tag:theconversation.com,2011:/au/topics/animal-sex-6504/articlesAnimal sex – The Conversation2023-10-03T18:00:41Ztag:theconversation.com,2011:article/2147512023-10-03T18:00:41Z2023-10-03T18:00:41ZFemale animals teach each other to choose unusual males – new research<figure><img src="https://images.theconversation.com/files/551381/original/file-20231002-17-gnxcqd.jpg?ixlib=rb-1.1.0&rect=23%2C4%2C3056%2C1934&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/elegant-peacock-colors-1255144876">alexroch/Shutterstock</a></span></figcaption></figure><p>My friend recently changed their favourite celebrity crush from Anna Kendrick to
Lily James. While some people could see the attraction, others might
not. So, what is it that attracts us to potential mates? A <a href="http://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002269">new study</a> suggests that female animals learn from other females to prefer distinctive males as mates.</p>
<p>Sexual selection involves the evolution of traits such as the <a href="https://www.youtube.com/watch?v=TTwT1-TpFhE">long, elaborate tail
of the peacock</a>. These traits have evolved to enhance an animal’s chance of attracting a mate, rather than to enhance survival ability. A weighty, colourful tail is a hindrance if you’re trying to evade a predator. </p>
<p>Generally, males compete for access to females, as the male investment in
offspring –- often only sperm -– is much less substantial than the effort a female puts in, producing eggs (which are larger than sperm), pregnancy and probably raising the offspring. So it is much more costly for a female to mate with a poor-quality male than vice versa, as the male can move quickly on to the next female. </p>
<p>This has led to the evolution of a plethora of sexually-selected male traits in the animal kingdom, and some very choosy females.</p>
<p>Historically, scientists focused on the interactions between males and often ignored the way females shaped evolution. But now researchers are paying more attention to the fascinating effects of female agency. </p>
<p>The new study, from Florida State University in the US, developed a mathematical model to try and explain some of the gaps in sexual selection theories.</p>
<p>First, it’s helpful to understand what research has shown about what makes a male attractive in the animal kingdom. In terms of looks, the males with the largest
<a href="https://www.sciencedaily.com/releases/2015/09/150901113432.htm">cheek pads or flanges</a> are most appealing to female orangutans, whereas <a href="https://www.sciencedirect.com/science/article/abs/pii/S0003347205809285">males with the longest “swords”</a> drive female swordtail fish wild. </p>
<h2>Not just about looks</h2>
<p>It is not just physical appearances that females choose their mates for.
The most <a href="https://www.theguardian.com/uk-news/2020/apr/16/fruity-and-irresistible-male-lemurs-wrist-scent-seduces-the-girls">pungent-smelling male ring-tailed lemurs</a> attract the most females. There are also plenty of examples of more complex traits, including the <a href="https://news.cornell.edu/stories/2018/11/females-drive-song-and-dance-male-birds-paradise">song and dance moves</a> of birds of paradise, or the crop-circle patterns made by male Japanese puffer fish to impress females.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/VQr8xDk_UaY?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<p>And, it’s not always the males that compete to be chosen by the females. Male stalk-eyed flies choose females based on the <a href="https://academic.oup.com/beheco/article/26/2/376/257321">distance between their eyes</a>, and find wider eyespans more attractive. </p>
<p>Current <a href="https://www.pnas.org/doi/10.1073/pnas.0608184103">theories of sexual selection</a> involve animals choosing mates due to signs they have good genes– like a long, elaborate tail. A strong, virile mate signals they will produce healthy offspring. </p>
<p>Alternatively, animals that have a hindersome trait, yet still survive, are probably of high genetic quality. There are also sensory bias theories, where mating preferences are a by-product of natural selection of the senses. </p>
<p>For example, <a href="https://link.springer.com/referenceworkentry/10.1007/978-3-319-19650-3_93">the hearing range of female Tungara frogs</a> is biased towards lower frequencies, coinciding with their preference for the lower-frequency calls produced by larger males.</p>
<p>Yet, none of these theories explain why there is so much variation in traits of males of the same species, or why female preferences can vary over time or within a species. </p>
<h2>Rare sex appeal</h2>
<p>The new study looked at whether females’ mate choices are based on watching more
experienced females choose their mates. It is well-known that animals can
learn from watching others. For example, young crows <a href="https://www.nature.com/articles/s41598-018-27405-1">learn how to make basic stick tools</a> by watching their parents. </p>
<p>Learning has also been shown in mate choice as <a href="https://royalsocietypublishing.org/doi/10.1098/rspb.2005.3054">females observing others</a> with
a male are more likely to choose that male themselves, or one with similar
traits.</p>
<p>The researchers based their model on the inferred attractiveness hypothesis,
where inexperienced females compare the qualities of a male, chosen by an
experienced female, to the qualities of all males. </p>
<p>For example, if a female sees an experienced female with a bright coloured male, she might seek a brightly coloured mate too. This would lead to bright colouration becoming more common, reducing variation. However, the inferred attractiveness hypothesis still doesn’t explain why there is so much divergence between males. </p>
<p>The US study was the first to consider that females may not be mind readers and may make mistakes when they try to copy other females. </p>
<p>In the hypothetical example illustrated below, the experienced female prefers males with redder plumage, so chooses to mate with male number three. The inexperienced female observer thinks that male number three’s long tail made him more attractive than his peers. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Illustration of two female birds choosing which male bird to mate with." src="https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=266&fit=crop&dpr=1 600w, https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=266&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=266&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=334&fit=crop&dpr=1 754w, https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=334&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/551696/original/file-20231003-17-oibla1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=334&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Illustration from the Florida State University study.</span>
<span class="attribution"><a class="source" href="https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.3002269">Florida State University/PLOS Biology</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The researchers used a computer simulation based on a mathematical model
of a population in which males mated with many females. The model involved males with two traits, with only two variants each (bright/dull colour and long/short tail length).</p>
<p>Their model showed that when females chose males based on the same trait that
the experienced female went for, these traits became fixed in the population, with
no variation. When females chose a more distinctive male, this caused the rare trait to become more common and, subsequently, less attractive. </p>
<p>This resulted in switches in female preferences over time, rather than a single attractive trait outcompeting the others.</p>
<p>We won’t know whether this happens in real life until scientists run field studies. But this is the first theory of sexual selection that explains how variation might be maintained in populations. </p>
<p>My current celebrity crush is Ryan Reynolds due to his good looks and
sense of humour. But I now wonder what other people might see in him – is it those eyes, or that smile, or something completely different?</p><img src="https://counter.theconversation.com/content/214751/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Louise Gentle works for Nottingham Trent University. </span></em></p>A new study modelled how a game of snog, marry, avoid, may play out in the animal kingdom.Louise Gentle, Principal Lecturer in Wildlife Conservation, Nottingham Trent UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2021462023-03-28T19:21:22Z2023-03-28T19:21:22ZA rare video of wombats having sex sideways offers a glimpse into the bizarre realm of animal reproduction<figure><img src="https://images.theconversation.com/files/517564/original/file-20230327-344-90i7il.jpg?ixlib=rb-1.1.0&rect=52%2C22%2C4940%2C3300&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>If you look at where wombats deposit their poo, you realise they must be able to perform some surprising acrobatics. It has always amazed me to see wombat scats on top of grass tussocks or logs, because I’ve always wondered how the stocky creatures must have manoeuvred themselves to put it there. </p>
<p>It turns out these sturdy marsupials also engage in a different kind of acrobatics: we recently received a video from Lyndell Giuliano and Andy Carnahan at Tomboye, New South Wales, who had filmed two wombats in the wild “doing the wild thing”! </p>
<p>While we know it happens, because there are baby wombats replenishing the population over time, it is not often humans get to witness such an event.</p>
<h2>A rare sighting of above-ground intimacy</h2>
<p>Scientists have <a href="https://rep.bioscientifica.com/view/journals/rep/145/6/R157.xml">previously documented wombat sex</a> in some detail. Prior to the observations noted in the review, it was believed to occur underground in the privacy of the burrow, which was presumably the reason why it was rarely observed. </p>
<p>While we still don’t know a lot about what wombats do get up to underground, wombats have been spotted mating above ground in the open! </p>
<p>In this scenario, the male wombat has been described to chase the female wombat, often biting her, and pushing her on to her side, before also laying on his side and mating with her. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/-qTKtHwlf6k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">A rare video of wombats mating, captured at Tomboye in NSW.</span></figcaption>
</figure>
<p>In this recorded “rom-com”, it appears only the male is on his side during mating.</p>
<h2>Violence and death</h2>
<p>Other marsupials are also quite aggressive during mating. The Tasmanian devil, probably not unsurprisingly given its name, is particularly aggressive. Males drag females into their den and hold them captive, sometimes for days. </p>
<p>Among the tiny, rodent-like antechinus and phascogales, males are so determined to mate with as many females as they can that it results in a huge surge of stress hormones, leading to complete organ failure, and <a href="https://theconversation.com/doing-it-to-death-suicidal-sex-in-marsupial-mice-18884">subsequently death</a>. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/doing-it-to-death-suicidal-sex-in-marsupial-mice-18884">Doing it to death: suicidal sex in 'marsupial mice'</a>
</strong>
</em>
</p>
<hr>
<p>This reproductive strategy, called “semelparity”, also occurs in salmon, and some frogs and lizards – but it is extremely rare among mammals.</p>
<p>And in the insect kingdom, it’s not unheard of for males to die after mating, though the reasons are often quite different.</p>
<p>Female praying mantises attract males and after the event decapitate their male companion and devour them. This cannibalism strategy enables females to produce more eggs. Males that are consumed are provided with a reproductive advantage through potentially increased numbers of offspring. </p>
<p>Male bees (drones) mate with females (queens) in the air. In some species, during the height of the “process”, the end of the male’s barbed endophallus is ejected from his body, and is retained with his sperm inside the queen. His work done, the male subsequently falls from the sky dead. </p>
<h2>Subterfuge and fusion</h2>
<p>Many animals use pheromones, essentially chemical messengers between members of the same species. </p>
<p>Some orchids have taken advantage of these chemicals, <a href="https://theconversation.com/warty-hammer-orchids-are-sexual-deceivers-107805">mimicking</a> the pheromones of female wasps. Male wasps are tricked into thinking they have found their female, and while mating with the flower, become coated in pollen. These wasps subsequently mate with another orchid, thus transferring the pollen, and subsequently the orchid is fertilised.</p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/warty-hammer-orchids-are-sexual-deceivers-107805">Warty hammer orchids are sexual deceivers</a>
</strong>
</em>
</p>
<hr>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A photo of a flower with pink petals and a surprisingly beelike central structure." src="https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=429&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=429&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=429&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=539&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=539&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517572/original/file-20230327-16-ueqfg3.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=539&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">In the same way some orchids imitate wasps, the bee orchid (Ophrys apifera) mimics the appearance and smell of a female bee to trick males into trying to mate with it.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/w/index.php?curid=48715235">Bernard Dupont / Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>There are some even more bizarre mating encounters in the animal world. The female deep sea angler fish allows the male to fuse with her, and sometimes even more than one male will fuse to the same female. </p>
<p>In return for sperm, the male anglerfish obtains nutrients from the female via their fused circulatory system. A truly “until death do us part” relationship.</p>
<h2>Survival of the quickest</h2>
<p>Among marsupials, some species (polyprotodonts) give birth to many more young than they can support. These so-called “supernumerary” young then race to reach a teat first, in what is essentially survival of the fittest. </p>
<p>The maximum number of young able to survive is therefore determined by the maximum number of teats. </p>
<p>Virginian opossums have 13 teats and can give birth to up to 56 young (although the average is more like 21), thus many newborns die shortly after birth, unable to find and attach to a teat. Tasmanian devils likewise produce an average of 39 young, but only have four teats, thus the maximum surviving litter size for devils is four. </p>
<p>Wombats are not polyprotodonts and only have two teats. However they usually only have one joey at a time.</p>
<h2>Surprising organs</h2>
<p>Much can be said for the phalluses of the animal world. None more so than <a href="https://pursuit.unimelb.edu.au/articles/solving-the-mystery-of-the-four-headed-echidna-penis">echidna penises</a> with their four heads, of which they only ever use two at a time. </p>
<p>Sharks likewise have two claspers, extensions of the pelvic fins which support internal fertilisation, of which they only utilise one during mating. Whale penises have been said to have been mistaken for deep sea monsters, or perhaps kraken tentacles, observed wrestling with their whale prey. </p>
<figure class="align-center ">
<img alt="An echidna" src="https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=411&fit=crop&dpr=1 600w, https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=411&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=411&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=517&fit=crop&dpr=1 754w, https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=517&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/517580/original/file-20230327-20-7zzwfq.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=517&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Male echidnas have a four-headed penis, while females have two uteruses.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Not to be outdone by the males, female marsupials have three vaginas and two uteruses. Two of the three vaginas are used for reproduction to allow sperm to travel up to fertilise the eggs. The third vagina, located between the other two, is for giving birth. </p>
<p>Female platypuses and echidnas have two uteruses and two ovaries. However, in platypus, only the left ovary is functional, and thus they only use one side of their reproductive tract for producing young. </p>
<h2>Back to the wombats</h2>
<p>As we have seen, there are a broad range of strategies animals use to produce young. Some reproductive strategies we are familiar with, others are deadly. </p>
<p>It puts the wombat video in perspective: our correspondents report the creatures walked away unharmed from the scenario, albeit with some love bites. At least everybody survived.</p><img src="https://counter.theconversation.com/content/202146/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Death by exhaustion, cannibalism, complete body fusion: across the animal kingdom, mating takes many strange forms.Julie Old, Associate Professor, Biology, Zoology, Animal Science, Western Sydney UniversityHayley Stannard, Senior lecturer, Charles Sturt UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1491742020-11-12T19:50:05Z2020-11-12T19:50:05ZFierce female moles have male-like hormones and genitals. We now know how this happens.<figure><img src="https://images.theconversation.com/files/368987/original/file-20201112-23-1ourijf.jpg?ixlib=rb-1.1.0&rect=0%2C5%2C4000%2C2652&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">Shutterstock</span></span></figcaption></figure><p>Moles live a tough life underground. As a result, they’ve evolved helpful adaptations, such as excavator-like claws. Female moles in particular have evolved an unusual strategy: high levels of the male hormone testosterone. </p>
<p>This is an evolutionary advantage. It produces stronger muscles for digging and foraging and aggression, to help mothers defend themselves and their young. </p>
<p>Most of the year, female moles look and behave like males. They have masculinised genitals, with no external vagina and an enlarged clitoris. But when mating season comes, testosterone levels drop and a vagina is formed; mating and birth follow.</p>
<p>How they accomplish this remained a mystery for a long time. But now, the <a href="https://science.sciencemag.org/content/370/6513/208.abstract">complete sequencing</a> of the mole genome has revealed the genetic tweaks underpinning this strange cycle in female moles, by which reproductive organs (gonads) develop and hormones are produced.</p>
<h2>Gonads and hormones</h2>
<p>Male development in humans and other mammals is determined by chromosomes (the structures within cells of living things that contain genes). Females have two copies of an X chromosome. Males have a single X and a male-specific Y chromosome. </p>
<p>In XY embryos, a gene called <em>SRY</em> on the Y chromosome intervenes in a network of another 60 genes. <em>SRY</em> turns on testis genes and turns off ovary genes to transform a ridge of cells into a testis. </p>
<p>In the testis, one cell type becomes specialised to make sperm and another (Leydig cells) makes male hormones, including testosterone. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-makes-you-a-man-or-a-woman-geneticist-jenny-graves-explains-102983">What makes you a man or a woman? Geneticist Jenny Graves explains</a>
</strong>
</em>
</p>
<hr>
<p>Testosterone is responsible for the most visible sex differences in males, such as bigger bodies, more muscle mass, male genitalia and more aggression. In XX embryos, an alternate pathway makes an ovary, which pumps out oestrogen.</p>
<p>So in mammals, different genetic pathways drive the same patch of embryonic tissue to become either an ovary or a testis. Generally, there’s no in-between. </p>
<p>But female moles have a patch of testis within their ovaries.</p>
<h2>An evolutionary balancing act</h2>
<p><a href="https://dev.biologists.org/content/118/4/1303">In 1993</a>, it was discovered the basis for “intersex development” in female moles is a gonad with both ovarian and testicular tissue. </p>
<p>Like other male mammals, male moles have a Y chromosome, bearing the <em>SRY</em> gene which directs testis formation. </p>
<p>Also like other mammals, female moles lack a Y chromosome. Curiously, however, instead of developing ovaries they develop “ovotestes”, with ovarian tissue at one end and testicular tissue at the other. </p>
<p>The ovarian tissue makes eggs and gets larger during breeding, then regresses. The testicular tissue is full of Leydig cells that make testosterone (but not sperm). Outside of breeding season, it expands until it’s larger than the ovarian end. </p>
<p>This explains why female moles have male-like genitalia, and are muscular and aggressive. But how does a patch of testis form in female moles if they have no <em>SRY</em> gene to trigger the process?</p>
<h2>Genetic tweaks behind ovotestis development</h2>
<p>To look for genetic changes that could allow this to happen, a global consortium of scientists <a href="https://science.sciencemag.org/content/370/6513/208.abstract">sequenced the entire mole genome</a>.</p>
<p>They found no differences between moles and other mammals in the protein products of the 60-odd genes involved in sex determination. However, they did discover mutations that altered the <em>regulation</em> of two of these genes in female moles.</p>
<p>One difference was found in the DNA sequences of a gene that’s vital for developing testes: <em>FGF9</em>. In all mammals, this gene switches on testis growth in XY embryos and inhibits genes that determine ovarian development. </p>
<p>In females of other mammals, the <em>FGF9</em> gene is turned off in the absence of <em>SRY</em>, but in female moles it stays on. </p>
<p>Genome sequencing revealed why: a big patch of DNA just upstream of <em>FGF9</em> is flipped around in moles. This inversion removes the usual control sequences from the gene, allowing it to stay on for longer in XX embryos.</p>
<p>The other gene impacted in female moles is <em>CYP17A1</em>, which codes for an enzyme that’s key to producing androgens (male hormones). In female moles, this gene and its surrounds have two extra copies, which increases testosterone output. </p>
<p>To show these genomic changes were indeed responsible for masculinising female moles, the researchers introduced them into mice, causing sex reversal and higher testosterone levels.</p>
<p>It’s important to note these evolutionary changes are in the <em>regulation</em> of gene activity, rather than in the regulation of protein products — which could compromise other normal functions.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Clownfish (_Amphiprioninae_)." src="https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=522&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=522&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368997/original/file-20201112-19-gi6jel.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=522&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Other than mammals, many marine animals have gender-bending tendencies. Clownfish always begin life as hermaphrodites carrying both female and male reproductive organs. Later in life, males can become female on an as-needed basis to mate with other males.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/szipiszopi/4919095469/in/photolist-8uFDGR-d6iqgf-2pEgAR-a3xGB7-4t985n-a3uQ4i-5cadh1-8ECGaX-3L8UN5-up9Mh-3L8UYN-Cu66xD-9pfPTN-8GLsLd-4kL2uD-4J1u8d-8FsdQs-dzruc-5DpDBY-5GUkSb-4kQ5YW-4kL38D-8WkdZn-KozKd7-qnrwnJ-coksCs-a6fGi2-2wMpjF-FPVyZy-38dWFC-PGX7c4-Kc29n9-gRkLPn-xDeEWy-EjqyJJ-6Y189v-rGsD6c-34WhVy-6YA5ez-gRkSs5-4g9oXn-pjBqbJ-6XX1Zc-nfKMRT-4kL1Ke-4J1sGC-5j4jKU-5LYxz4-aad1RH-ayLz3G">Istvan/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/what-we-learn-from-a-fish-that-can-change-sex-in-just-10-days-129063">What we learn from a fish that can change sex in just 10 days</a>
</strong>
</em>
</p>
<hr>
<h2>What this means for sex and evolution</h2>
<p>Since mammals, including humans, develop as either males or females, we’ve been accustomed to regard testis or ovary development in the embryo as strict alternatives, depending on an on/off switch (the presence or absence of the Y chromosome and <em>SRY</em> gene). </p>
<p>But we now know there’s a complex gene network full of checks and balances that is the basis for alternate pathways of sexual development.</p>
<p>There are many studies of human babies born with <a href="http://theconversation.com/boy-girl-or-dilemmas-when-sex-development-goes-awry-49359">mutations in one of these genes</a>. This points to a more complex picture of the wiring behind the “switch” responsible for variation in human sexual development. </p>
<p>There are fierce females in other mammal species, too. Female spotted hyenas are <a href="https://www.sciencedirect.com/science/article/abs/pii/S0018506X00916349">bigger and more dominant</a> than males and have male-like genitalia. We don’t know how this change works at a genetic level. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="A female spotted hyena in the wold." src="https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/368992/original/file-20201112-17-1axmrqx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The spotted hyena, <em>Crocuta crocuta</em> (also known as the ‘laughing hyena’) is native to sub-Saharan Africa. In females such as this one, the clitoris is shaped and positioned like a penis that can become erect.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The downside of this is that mating is tricky. Cubs are birthed through the female’s narrow phallus. Mothers and/or cubs often die during this fraught process.</p>
<p>So while these larger, more aggressive females rule the hyena roost and get first pick at meals, like most things in nature, it seems this comes at a price.</p>
<p>Big fierce female moles and hyenas remind us the natural world, as always, features unique evolutionary differences — enlightening our view on human variation.</p><img src="https://counter.theconversation.com/content/149174/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jenny Graves receives funding from the Australian research Council. </span></em></p>Female moles evolved to have high testosterone levels, making them fiercer diggers and mothers. Female hyenas share this trait, but it means they must give birth through a male-like phallus.Jenny Graves, Distinguished Professor of Genetics and Vice Chancellor's Fellow, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1282842019-12-11T12:44:19Z2019-12-11T12:44:19ZLeopard slugs mate in the most beautifully bizarre way – and nobody knows why<figure><img src="https://images.theconversation.com/files/306088/original/file-20191210-95125-sj2zwu.jpg?ixlib=rb-1.1.0&rect=0%2C7%2C4710%2C2987&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Beautifully bizarre.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/mating-leopard-slugs-limax-maximus-australia-1435271348">Ken Griffiths/Shutterstock</a></span></figcaption></figure><p>Under the cover of night, two large leopard slugs begin to court, circling each other, before climbing single-file up a tree or onto a rock. They lower themselves on a mucus rope, while entwining their bodies in a strictly anti-clockwise fashion.</p>
<p>Both slugs then push out and entwine two overly-sized penises from openings on the side of their head, before exchanging sperm that may later fertilise each of their eggs. Or, perhaps be eaten. Eventually, one slug crawls off and the other follows, eating the mucus trapeze as it goes.</p>
<p>The astonishing sex lives of leopard slugs, or <em>Limax maximus</em>, have long been recognised by naturalists and frequently feature in <a href="https://youtu.be/wG9qpZ89qzc">wildlife documentaries</a>. But while their carnal dance has mesmerised millions, nobody knows why they mate in this most bizarre way.</p>
<p>This is because slug sex science has rarely attracted anything other than observational study. Fortunately for our curiosity, there are a few <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">noble individuals</a> who have taken time to understand the mating habits of snails and slugs, and <a href="http://www.joriskoene.com/">whose research</a> can give us some valuable clues.</p>
<figure>
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<p>It’s well known that leopard slugs, like the majority of land-based snails and slugs, are hermaphrodites – meaning that both sexual organs are contained in the same individual. Yet, self-fertilisation is generally not the <a href="https://zslpublications.onlinelibrary.wiley.com/doi/abs/10.1017/S0952836905007648">preferred option</a>. This is likely because natural selection favours mating with another individual to avoid the loss of health, fertility and fitness associated with <a href="https://www.sciencedirect.com/science/article/pii/S0169534716301586">inbreeding</a>.</p>
<p>Even though they can choose whether to mate as male or female, most slugs and snails mate as male and female at the same time. They can also <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">store sperm</a> for months and even years, and so don’t always need to receive sperm if they have previously mated with a better partner. They can have the best of both worlds by choosing to eat and digest most of the sperm, while retaining just enough to fertilise their eggs.</p>
<p>We also know why leopard slugs turn anti-clockwise when mating. Just like human hearts are <a href="https://www.theguardian.com/science/blog/2016/sep/08/situs-inversus-and-my-through-the-looking-glass-body">nearly always</a> to the left hand side in our bodies, a slug’s body is also asymmetric. This is most obvious during mating, when the genitals emerge from the right side of the head. This asymmetry makes leopard slugs turn anti-clockwise in synchrony during courting and mating – and is also what made rare left-coiling snail Jeremy <a href="https://web.archive.org/web/20171020222103/http://www.bbc.co.uk/bbcthree/item/249e54d9-7c5c-451e-940c-7826f6dd2a14">a media sensation</a> in his/her <a href="https://www.npr.org/sections/thetwo-way/2017/05/17/528796939/tragic-love-triangle-is-sad-for-lonely-rare-snail-still-good-for-science">search for love</a>.</p>
<h2>The rest is mystery</h2>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=903&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=903&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=903&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1135&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1135&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306207/original/file-20191210-95138-q0ny8k.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1135&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">It’s a long way up from there.</span>
<span class="attribution"><a class="source" href="https://flickr.com/photos/kongniffe/48904576193/">Inge Knoff/flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>The rest of their elaborate mating behaviour is less well understood. It might be that that <a href="https://www.youtube.com/watch?v=UOcLaI44TXA">communication and cooperation</a> are important aspects of sexual behaviour in the mollusc world, beginning with the head-to-tail <a href="https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12023">trail-following</a>. The long mucus trapeze could be an example of sexual evolution going into overdrive to signify commitment to what’s to come, making sure that any mating efforts won’t be wasted. The spiral entwinement between mating slugs may also facilitate close physical contact and commitment, minimising the risk of sudden withdrawal.</p>
<p>But this behaviour is also more sinister than it first appears. Some slugs and snails engage in hormone warfare or sexual conflict to increase their chances of fertilising their mate. For example, as artistically interpreted by <a href="https://www.youtube.com/watch?v=BckqviVaWl0">Isabella Rossellini</a>, many snails (including the common garden variety) <a href="https://bmcevolbiol.biomedcentral.com/articles/10.1186/1471-2148-5-25">stab each</a> with <a href="https://en.wikipedia.org/wiki/Love_dart">love-darts</a>, transferring hormones to improve the chances that sperm are used for fertilisation. The field slug <em>Deroceras</em>, seen below, <a href="https://youtu.be/b70CGCdeP3I?t=180">flicks and strokes</a> its partner with what looks like a <a href="https://bioone.org/journals/american-malacological-bulletin/volume-23/issue-1/0740-2783-23.1.137/A-review-of-mating-behavior-in-slugs-of-the-genus/10.4003/0740-2783-23.1.137.short">sticky slug blanket</a> for the same reason.</p>
<figure>
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</figure>
<p>The leopard slug’s beautiful entwinement could be another manifestation of this sexual coercion, maximising surface area for hormone transfer. The long penises – which can be <a href="http://www.scholarpedia.org/article/Gastropod_reproductive_behavior">60 to 90cm</a> long in one <a href="http://www.scholarpedia.org/article/File:Limax_Long_Penes.jpg">Italian version</a> of the leopard slug – may also be another extreme result of an evolutionary arms race to improve the prospects of fertilisation.</p>
<figure class="align-right ">
<img alt="" src="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=1067&fit=crop&dpr=1 600w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=1067&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=1067&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1341&fit=crop&dpr=1 754w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1341&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/306350/original/file-20191211-95159-bxkp7.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1341&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Yes, that’s all penis.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Accoppiamento_fra_lumache_2.JPG">Viktor Volkov/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<p>Why they intertwine so intricately is another matter. It could be that the beautiful complexity makes it more difficult for one slug to “cheat” by giving sperm and then not receiving some in return.</p>
<p>In the absence of direct study, the above explanations can only be considered speculation. The truth is that science doesn’t yet have a firm handle on the fascinating sex rituals of leopard slugs.</p>
<h2>More than voyeurism</h2>
<p>Scientists are not just being voyeuristic when we say we’d like to unravel the mysteries of slug sex. Aside from just understanding the wonder and beauty of the behaviour, there are potential benefits.</p>
<p>Some species of slugs are <a href="https://www.rhs.org.uk/advice/profile?pid=228">farm and garden pests</a>, eating holes in leaves, stems, flowers, tubers and bulbs and causing particular damage to new growth. With the pending ban of key pesticides for agricultural use in some countries, including the active ingredient in <a href="https://www.gardenorganic.org.uk/news/metaldehyde-slug-pellets-ban-overturned">slug pellets</a>, there is growing pressure to find other ways to control their spread. One way could be to identify otherwise harmless chemicals that interfere with their sex lives. A contraceptive sheath for slugs, so to speak.</p>
<p>Another approach could be to question why some of the slugs that cause the most agricultural nuisance forgo sex completely, especially in northern latitudes. Lack of sex reduces genetic variation, which causes crops such as potatoes and bananas to suffer from disease outbreaks. Studying the self-contained reproductive habits of slugs may reveal a similar vulnerability that could be exploited to control their numbers.</p>
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<p>There may of course also be benefits which we can’t anticipate. So just as people champion trees, bees and butterflies, we need more slug enthusiasts of <a href="https://www.bbc.co.uk/news/entertainment-arts-46399187">all kinds</a> to help unravel their mucosal mysteries, including backyard explorers who can contribute to <a href="https://www.rhs.org.uk/slugssurvey">citizen science</a> studies. </p>
<p>Of course, if you are already a convert, then how about a leopard slug sex ornament for the <a href="http://www.furaffinity.net/view/25744884/">Christmas tree</a>?</p><img src="https://counter.theconversation.com/content/128284/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Angus Davison received funding from the Biotechnology and Biological Sciences Research Council</span></em></p>Scientists don’t just want to unravel the mysteries of slug sex for voyeurism.Angus Davison, Associate Professor and Reader in Evolutionary Genetics, University of NottinghamLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/901272018-02-05T11:12:04Z2018-02-05T11:12:04ZWhat medieval artists teach us about animal sex<figure><img src="https://images.theconversation.com/files/204802/original/file-20180205-19952-1aq6tob.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/frog-sex-animal-mating-113047891?src=k_e5EX9xZX31WhersYJh0g-1-8">CRS PHOTO/Shutterstock.com</a></span></figcaption></figure><p>The prevailing view is that animals mainly have sex to reproduce. Until recently, therefore, scientists assumed that animals were relentlessly heterosexual. This is the message conveyed by countless zoos, wildlife documentaries, books and films. Think <a href="http://www.lurj.org/issues/volume-1-number-2/penguins">March of the Penguins</a> or 2014’s controversial <a href="http://www.bilerico.com/2014/04/no_gay_animals_on_noahs_ark.php">Noah</a>. Such representations perpetuate the belief that animals are best seen through the lens of human “norms” of gender, sex and family.</p>
<p>The presumed “heterosexuality” of animals has also traditionally provided a backhanded justification for regulating human sexual activity. Acts of homoeroticism or gender bending get cast as “unnatural” insofar as such things aren’t perceived as being clearly observable in other species.</p>
<p>But arguing against these viewpoints, biologists such as <a href="https://books.google.co.uk/books/about/Biological_exuberance.html?id=5EzaKnlxLLgC">Bruce Bagemihl</a> and <a href="https://books.google.co.uk/books/about/Evolution_s_Rainbow.html?id=6O9Wj8E_PZkC&redir_esc=y">Joan Roughgarden</a> have begun putting forward evidence that animal sexuality comprises an array of behaviours, gender expressions and body types. In fact, reproduction is marginal to many species. Scientists impose human categories on animals at their peril. And increasingly, popular culture is also getting behind these moves. The web is inundated with articles and blog posts on such topics as <a href="http://www.buzzfeed.com/mjs538/the-25-gayest-animals#.dlV88Yxzx">The 25 Gayest Animals</a> or <a href="http://www.transsexual.org/anec1.html">Our Transsexual Pets</a>. A search on YouTube turns up a wealth of <a href="https://www.youtube.com/watch?v=kYRIO4tz2gA">related footage</a>.</p>
<figure>
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<p>Yet a historical perspective on these issues is often lacking. Categories such as “gay” or “trans” are not ageless absolutes, after all. The word “heterosexuality” itself only began being used around 1900, initially in medical circles: a <a href="http://outhistory.org/exhibits/show/heterohomobi/merriam2">1923 dictionary</a> defines it as a “morbid” sexual passion for the opposite sex.</p>
<p>And what seems on the surface to be a relatively recent development – the discovery of expressions of queerness in the animal kingdom – turns out to have a long and dynamic history. It’s important to take a long view on the issue.</p>
<h2>Animal sex in the Middle Ages</h2>
<p>During the Middle Ages, discussions of animal sex proliferated in <a href="http://bestiary.ca/">bestiary</a> manuscripts. Designed to present a Christianised interpretation of the natural world, these volumes perpetuated a traditional Noah’s ark view of biology. But they also often featured creatures that don’t seem to fit the “heterosexual” mould.</p>
<p>For example, the <a href="http://bestiary.ca/beasts/beast153.htm">hyena</a>, which medieval scholars thought possessed male and female sexual organs that the animal used indiscriminately, is depicted in <a href="http://www.abdn.ac.uk/bestiary/translat/11v.hti">some illustrations</a> with enlarged humanoid genitals. Medieval Christian commentators interpreted the beast’s gender-switching behaviour as a figure for “Jewish” duplicity as well as sodomy.</p>
<p>Conversely, the male <a href="http://bestiary.ca/beasts/beast152.htm">beaver</a>, believed to castrate itself to escape human hunters, was likened to a chaste man of God. Others whose sexual habits were turned into spiritual lessons included <a href="http://bestiary.ca/beasts/beast267.htm">vipers</a> (presented as serial adulterers with a taste for fellatio) and <a href="http://bestiary.ca/beasts/beast233.htm">vultures</a> (which allegedly bred without sexual union).</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=606&fit=crop&dpr=1 600w, https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=606&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=606&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=761&fit=crop&dpr=1 754w, https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=761&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/204803/original/file-20180205-19956-1ujmmnp.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=761&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Depiction of a black vulture, 1893.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:The_royal_natural_history_(1893)_(14784868845).jpg">Wikimedia Commons</a></span>
</figcaption>
</figure>
<p>Animals allowed medieval audiences to contemplate taboos such as oral sex or promiscuity, while casting the religious ideal of chastity as a “natural” human activity. Bestiaries were therefore preoccupied less with “heterosexuality” as such than with the need for all humans, regardless of gender, to channel their desires towards the man upstairs.</p>
<p>Medieval bestiaries set the stage for a lively debate on sex and gender among humans. Arguably, a similar conversation is playing out today. The presumed heterosexuality of animals is giving way to glimpses of gender and sexuality that exceed our human-centred grids.</p>
<h2>The medieval science of sex</h2>
<p>Books translating and commenting on the biological works of the ancient philosopher <a href="https://plato.stanford.edu/entries/aristotle/">Aristotle</a> also sometimes adopted such perspectives. Like some of the images circulating in the bestiaries, these illustrations presented a kaleidoscopic view of creaturely coitus.</p>
<p>For instance, in the 13th century, <a href="https://plato.stanford.edu/entries/albert-great/">Albert the Great</a> wrote an influential commentary on Aristotle’s <em>De Animalibus</em>. A <a href="http://gallica.bnf.fr/ark:/12148/btv1b85409542.r=latin+16169.langFR">student copy of Albert’s text</a>, owned by scholars at the Sorbonne in Paris, contains a series of images depicting copulating creatures.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=428&fit=crop&dpr=1 600w, https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=428&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=428&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=538&fit=crop&dpr=1 754w, https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=538&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/204804/original/file-20180205-19944-icoein.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=538&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A copy of Albert the Great’s De Animalibus.</span>
<span class="attribution"><a class="source" href="https://en.wikipedia.org/wiki/File:Firenze,_alberto_magno,_de_animalibus,_1450-1500_ca._cod_fiesolano_67,_01.JPG">Sailko/Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>One page illustrates a section of the text where Albert is discussing what he calls the great “diversity” of nature. In the margins viewers are afforded a glimpse of the sexual dimension to this diversity. Fish mate belly-to-belly. Birds mount or touch beak-to-beak. A donkey gets astride a whinnying mare. Serpents get themselves into a real tangle.</p>
<p>Meanwhile, in the centre of the same page, a pair of naked humans, framed in a gold initial, are represented locked in an intimate embrace, the lower halves of their bodies chastely obscured by the decoration. This seemingly corresponds to Albert’s argument that whereas non-humans mate noisily and without shame, humans do it silently and in private.</p>
<p>Diversity, then, is crucial to visions of animal sex in medieval art. Not only do humans differ from other animals in the way they copulate, but artists also imagined a spectrum of possibilities among nonhuman animals.</p>
<h2>Monstrosities</h2>
<p>Another scene in the same book, focusing on generation and sex difference, shows how even within the human animal there exists sexual variety. In the accompanying text Albert asserts that what he terms “monstrosities” usually result from acts of intercourse between animals of different species but with similar natures. But some “monsters” result from a multiplication of members, as in those humans who are born possessing both sexes.</p>
<p>A page at the beginning of the relevant section features an image of a naked male touching the stomach of a heavily pregnant female – a conventional image of the end to which reproductive sex leads. </p>
<p>Corresponding to Albert’s description of the “monstrosity” he calls “hermaphrodite”, however, the illustrator has also included a rare medieval depiction of an intersex person possessing both male and female genitalia.</p>
<p>What’s more, the same margins also feature other examples of monstrous births, depicted as human-animal hybrids, including a lion-man with a bearded human head. Such imagery suggests that even within the sphere of reproduction there is potential for variety and multiplicity.</p>
<p>Such images in medieval art draw attention to the fact that we humans, too, are stranger and more complicated than we sometimes suppose. It’s a lesson from which those who persist in finding reflections in “nature” of human categories of gender and sexuality today can surely learn.</p>
<hr>
<p><em>The next edition of our podcast The Anthill is on sex. Subscribe <a href="https://theconversation.com/uk/podcasts/the-anthill">here</a>.</em></p><img src="https://counter.theconversation.com/content/90127/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Robert Mills does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>How do different species have sex? Medieval illuminated manuscripts contain some surprisingly varied depictions.Robert Mills, Professor of Medieval Studies, UCLLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/465992015-09-02T00:01:15Z2015-09-02T00:01:15ZThe secret sex life and pregnancy of a seahorse dad<figure><img src="https://images.theconversation.com/files/93394/original/image-20150831-13178-11rdncu.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Tagged male seahorses in the laboratory aquarium.</span> <span class="attribution"><span class="source">Camilla Whittington</span>, <span class="license">Author provided</span></span></figcaption></figure><p>When it comes to bending gender stereotypes, <a href="http://animals.nationalgeographic.com.au/animals/fish/sea-horse/">seahorses</a> and their relatives would have to be one of the most extreme examples. These fish swap the traditional roles of mums and dads as they are the only animals where the males get pregnant.</p>
<p>Even though fish don’t have the external genitalia that we normally associate with males and females, we can still distinguish between them. That’s because we <a href="https://theconversation.com/male-female-ah-whats-the-difference-12786">classify animal sexes</a> according to the size of the <a href="http://biology.about.com/od/geneticsglossary/g/gametes.htm">gametes</a> (sex cells) they produce. Males produce the sperm (the smallest gametes) and females produce the eggs (the biggest gametes).</p>
<p>But in seahorses, the sperm-producers are also the ones that get pregnant. The female transfers her eggs to the male’s abdominal pouch, made of modified skin. The male releases sperm to fertilise the eggs as they enter, before incubating them for 24 days until they are born.</p>
<h2>Investigating pregnant dads</h2>
<p>We’ve known for a long time that seahorse males get pregnant. But until now, we haven’t known much about what actually goes on inside the male pouch.</p>
<p>In new research published this week in <a href="http://mbe.oxfordjournals.org/content/early/2015/09/01/molbev.msv177.abstract">Molecular Biology and Evolution</a>, just in time for <a href="http://www.timeanddate.com/holidays/australia/father-day">Father’s Day</a>, our team investigated whether male seahorses contribute more to their offspring than just sperm and a container to gestate the embryos.</p>
<p>We took samples from male pouches at different stages of pregnancy and then used new DNA sequencing technologies to assess how pouch gene expression changes.</p>
<p>This is the first time that these technologies have been used to examine the full course of pregnancy in any animal. It allowed us to examine the genetic basis of the processes going on inside the pregnant pouch.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=874&fit=crop&dpr=1 600w, https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=874&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=874&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1099&fit=crop&dpr=1 754w, https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1099&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/93399/original/image-20150831-13172-1i9qf3z.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1099&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Male seahorses give birth to hundreds of babies after a short pregnancy.</span>
<span class="attribution"><span class="source">Rudie Kuiter, Aquatic Photographics</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>We found that seahorse pregnancy is incredibly complex: more than 3,000 different genes are involved. When we examined them in detail, we found genes involved in many different processes. We even discovered genes allowing seahorse fathers to provide nutrients to their developing embryos.</p>
<p>In particular, fathers supply energy-rich fats and calcium to allow the embryos to build their tiny skeletons and bony body rings that sit just under the skin. Other pouch genes help the males remove wastes produced by the embryo, such as carbon dioxide and nitrogen.</p>
<p>Seahorse dads even seem to protect embryos from infection, producing antibacterial and antifungal molecules to ward off pathogens.</p>
<h2>Preparing for birth</h2>
<p>Seahorse birth is even more of a mystery than seahorse pregnancy, and we were excited to find that some of those 3,000 genes also prepare the father and the embryos for labour.</p>
<p>With around one week to go, instead of packing a hospital go-bag, seahorse dads start producing hatching signals. These signals cause the embryos to hatch out from their thin membranes and swim freely inside the brood pouch.</p>
<p>As the embryos take up more room, the pouch begins to stretch, much like the belly of a very pregnant human. The hormone oestrogen also gets involved and these combined forces produce cascading genetic signals that produce birth.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/MsHCqrrU-Gk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How many offspring can a seahorse dad give birth to?</span></figcaption>
</figure>
<h2>Similarities across animal pregnancies</h2>
<p>So seahorse dads make excellent “mums”, performing many of the same functions that occur in females during mammalian pregnancy and birth. Strikingly, many of the seahorse genes are similar to those in other pregnant animals.</p>
<p>This is surprising because pregnant mammals, reptiles and other fish all incubate their embryos inside the female reproductive tract. Their pregnancies have evolved entirely independently of seahorse pregnancy, millions of years apart, and yet we see the same processes occurring.</p>
<p>Why would the genes controlling male and female pregnancies be similar? We think that this is because gestation presents the same set of complex challenges to the parent, regardless of species.</p>
<p>Seahorse dads, just like human mums, need to make sure they can provide oxygen and nutrients to their embryos. We do it with a placenta inside a uterus and seahorse dads do it with thickened skin inside a pouch, but we’ve used similar genetic instructions to get there.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/93408/original/image-20150831-15790-oxm3i6.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">All thanks to dad for the birth of juvenile seahorses, here being reared in the laboratory.</span>
<span class="attribution"><span class="source">Camilla Whittington</span>, <span class="license">Author provided</span></span>
</figcaption>
</figure>
<p>Our findings raise the possibility that the same genes have been repeatedly and independently recruited for pregnancy across vertebrate animals – a remarkable display of <a href="https://theconversation.com/au/topics/convergent-evolution">convergent evolution</a>.</p>
<p>We’ve shown how seahorse dads use thousands of genes working in concert to provide the ideal environment for embryonic growth. This is a breakthrough in our understanding of the genetics of seahorse reproduction, although much follow up work is required to definitively test the functions of every one of those genes.</p>
<p>But we still haven’t solved the mystery of why seahorse fathers get pregnant given that females have that responsibility in every other animal. Seahorse mums still contribute nutrient-rich egg yolks that feed developing embryos, but their responsibility for their offspring ends at mating.</p>
<p>So seahorses, with their bizarre reproductive strategies, still have plenty more to offer evolutionary biologists.</p><img src="https://counter.theconversation.com/content/46599/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Camilla Whittington does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s long been known that it’s the male seahorse that gives birth to the young. But what role the father plays in the gestation is only now being revealed.Camilla Whittington, Postdoctoral Researcher in Comparative Genomics, University of SydneyLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/359682015-01-07T14:51:11Z2015-01-07T14:51:11ZSome creatures use electricity and vibrations in sex (and this can be dangerous)<figure><img src="https://images.theconversation.com/files/68349/original/image-20150107-1968-1djev3k.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Finding mates using electric signals.</span> <span class="attribution"><a class="source" href="http://www.wikiwand.com/en/Ghost_knifefish">Derek Ramsey</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span></figcaption></figure><p>Most animals use touch, smell, hearing, taste and sight to identify and attract a mate (that goes for humans too). But some species have additional and unusual weapons in their sexual armoury – the ability to sense vibrations and electric signals which indicate that a similar creature is in the vicinity. </p>
<p>Of course, it takes one to know one – and these signals are usually invisible to other species that don’t possess the requisite receptors needed to pick up on these vibrations and signals. So while some electric fish have specialised cells to send and receive messages to members of their own species, other fish remain oblivious to this secret courtship within their neighbourhood.</p>
<p>But while this is usually an advantage, sometimes these secret courting signals can be picked up on by predators.</p>
<h2>Ghost knifefish and electric sex</h2>
<p>The ghost knifefish, native to freshwaters of South America, are quite unusual. They have developed a unique way of finding mates in dark, turbid waters where their vision may be compromised: they <a href="http://epub.uni-regensburg.de/2108/1/ubr00728.pdf">communicate with each other using electricity</a>.</p>
<p>Brown ghost knifefish (<em>Apteronotus leptorhynchus</em>) have a specialised electric organ in their tail that generates a signal called Electric Organ Discharge (EOD). One fish produces an electric field to send a message, and the receiver uses electroreceptors distributed over its skin to interpret the signal. The frequency and waveform of the message give it a unique code that conveys recognition, aggression, location of food, warnings of danger, and in some cases, even courtship.</p>
<p>Male and female knifefish recognise each other from their <a href="http://www.ncbi.nlm.nih.gov/pubmed/9691480">unique EOD frequencies</a> (EODfs). Males produce higher-frequency signals in the range of 800-1100 Hz, whereas females emit signals in the range of 600-800 Hz. </p>
<p>EODfs do more than just help these fish identify the opposite sex. They may even be indicators of “male quality”. Female knifefish generally prefer males with high EODfs, perhaps because they tend to have <a href="http://www.sciencedirect.com/science/article/pii/S0003347202920191">larger bodies</a> and <a href="http://www.ncbi.nlm.nih.gov/pubmed/12122465">gain precedence</a> over others while competing for limited resources like food.</p>
<p><a href="http://biology.mcgill.ca/faculty/krahe/">Rüdiger Krahe</a> of McGill University is an expert on communication in weakly electric fish and has recently demonstrated how environmental changes can manipulate mating behaviour in ghost knifefish. In <a href="http://www.sciencedirect.com/science/article/pii/S0018506X11002145">his experiment</a>, male and female fish were housed in the same aquarium for a month, during which researchers simulated breeding conditions within the aquarium by imitating a rainy environment – knifefish <a href="http://www.ncbi.nlm.nih.gov/pubmed/14692503">prefer to breed in the rainy season</a>. They recorded the electric signals produced by the fish using electrodes placed on the fish and in the water. They found that in the rainy environment, males increased their EODfs, most likely to attract females.</p>
<p>The same team also performed a second experiment in which they housed one group of male knifefish in isolation and a second group surrounded by other male and female knifefish. The males housed in a social environment had higher EODfs. Thus, ghost knifefish not only use electric signals to find their partners but also are capable of continuously adjusting the nature of these signals according to changing environmental conditions.</p>
<h2>Killed by vibrations</h2>
<p>Some species of insects recognise their own kind with vibrations that convey specific information. The male leafhopper, for instance, transmits low-frequency vibrations through plants to recognise, locate and approach females. The insects possess specialised receptor cells in their legs to detect acoustic mating signals. However, unlike electric signals, these vibrational signals sometimes stand out from background noise and can therefore be <a href="http://beheco.oxfordjournals.org/content/18/1/236.abstract">intercepted by predators</a>.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=207&fit=crop&dpr=1 600w, https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=207&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=207&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=260&fit=crop&dpr=1 754w, https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=260&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/68348/original/image-20150107-1971-hkrwc4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=260&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Tangle-web spiders (right) use the leafhopper’s (left) sexual vibrational signals to locate and kill them.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/gails_pictures/6931081369">JamesKLindsey and gailhampshire</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Tangle-web spiders prey on leafhoppers – and scientists at Cardiff University have shown that they locate their prey by <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2011.05038.x/full">exploiting the leafhopper’s sexual vibrational signals</a>. In the study, spiders were placed on a plant and exposed to recordings of the leafhopper’s mating calls, generated using a vibrating device attached to the plant. These signals were adjusted to match the amplitude and frequency of the leafhopper’s natural calls.</p>
<p>The researchers found that the spiders changed their behaviour in response to different signals. In the presence of such vibrations, the spiders spent more time on the plant and began to display typical foraging behaviour. They started to make their way towards the vibrating leaf, probably because they thought it was a source of food. This directed movement was only observed in the presence of the male calling signal. The authors postulate that since male vibrational calls are more conspicuous and have higher amplitudes (that is, stronger vibrations) than female calls, spider foraging behaviour may be influenced by the difference. Wolf spiders that do not prey on leafhoppers remained unaffected by the insect’s vibrational signals in this experiment.</p>
<p>Vibrational signalling in animals has been well documented, but this is the first evidence for its use in predator-prey relationships. It is likely that there are other predators that intercept sexual vibrational cues to locate and capture their prey, and that this tactic is an <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2011.05038.x/full">unrecognised driver of evolution</a> in many invertebrates.</p><img src="https://counter.theconversation.com/content/35968/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sana Suri blogs at <a href="http://neurobabble.co.uk">http://neurobabble.co.uk</a>.</span></em></p>Most animals use touch, smell, hearing, taste and sight to identify and attract a mate (that goes for humans too). But some species have additional and unusual weapons in their sexual armoury – the ability…Sana Suri, PhD student, University of OxfordLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/275622014-06-04T05:02:25Z2014-06-04T05:02:25ZFrom monogamous termites to male-eating spiders, an ecologist explains<figure><img src="https://images.theconversation.com/files/50138/original/4sggkyg5-1401815209.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Mating pair of Meconema bushcrickets, female to the left, with male’s genital tongs highlighted in purple</span> <span class="attribution"><span class="source">C. Roesti</span></span></figcaption></figure><p>The Conversation organised a public <a href="http://www.reddit.com/r/science/comments/276ygd/science_ama_series_hi_im_james_gilbert_a/">question-and-answer session</a> on Reddit in which James Gilbert, postdoctoral researcher at the University of Sussex, explained weird and stunning insect reproductive strategies.</p>
<hr>
<p><strong>What is an example insect reproductive strategy that you would describe as especially ‘creative’?</strong></p>
<p>I use the word “creative” because that’s precisely what some of the strategies evoke to me. However, I must stress that it is evolution being “creative” here – I’m not trying to claim that the individual male is being “creative” or even evaluating what he is doing. </p>
<p>I think one embodiment of evolutionary creativity in the arms race over mating would be a <a href="http://blogs.discovermagazine.com/notrocketscience/2010/08/10/male-water-striders-summon-predators-to-blackmail-females-into-having-sex/#.U42_kZSwKFc">recently discovered behaviour</a> of unwanted suitors in water striders. These insects sit on top of water, using surface tension to stop them falling in. But their vibrations are sensed by predators underneath the water, like fish. When mating, the male climbs on the female’s back and is relatively safe from predators, but she can still be snapped up. Now, when mating, the female has a virtually impregnable hatch that covers her genital area that allows her (all else being equal) effectively to control completely who gets to mate. This presents a problem to unwanted males. Their solution is to climb on top of the female and produce vibrations that attract predators until the female “consents” to open the hatch and let them mate. Effectively this is insect blackmail. Although the individual male may not realize what he’s doing, in evolutionary terms I think this is an amazingly creative – if horrible – solution to what might otherwise have been a very difficult problem for these males to overcome.</p>
<p><strong>My bug-loving 7-year-old asks: how do worms have babies?</strong></p>
<p>Earthworms are hermaphrodites, which means each individual worm is both male and female. Two worms thus fit together by lying in opposite directions. After mating, both worms ooze away, and after a while each one produces a ring-shaped cocoon around itself into which it deposits the fertilised eggs, and then slips out backwards. The cocoons are like little eggs in the soil. I believe quite a few are parthenogenetic too, that is there are only ever females, and they have babies without mating.</p>
<p><strong>Is there any truth to the theory that caterpillars and butterflies evolved as separate species and then converged?</strong></p>
<p>An extraordinary hypothesis. However, it was very controversial and the hypothesis has since been <a href="http://www.pnas.org/content/106/47/19906.full?origin=publication_detail">rejected</a>.</p>
<p>For those that didn’t see it, the <a href="http://www.pnas.org/content/106/47/19901.short">original paper</a> proposed that caterpillars were originally their own separate lineage of animals that were related to an extremely odd kind of animal called a velvet worm, and that these velvet worms somehow hybridised with butterfly-like insects to produce an organism with a larva like a caterpillar and an adult like a butterfly.</p>
<p>On one hand this appears to be science working extremely well: the author proposes a hypothesis, makes some predictions, and the predictions are taken by other scientists and tested, and found to be false – job done.</p>
<p>However, in this case the hypothesis was absolutely outlandish and went against a ton of existing evidence – furthermore, the predictions were very easy to test, and really the author should have taken the extra step of testing them first to provide some concrete evidence for the claim, before advancing something so controversial and unfounded – so as not to waste the time of other authors who have better things to do than test wild theories.</p>
<p>As for how we really think metamorphosis evolved – well, that remains <a href="http://www.scientificamerican.com/article/insect-metamorphosis-evolution/">somewhat of a mystery</a>.</p>
<p><strong>Do you have examples of forced reproduction in insects?</strong></p>
<p>Traumatic insemination, as <a href="https://theconversation.com/invertebrates-inject-a-bit-of-romance-during-sex-by-stabbing-each-other-24154">practised by bedbugs</a>, is perhaps the most horrific – and there are <a href="http://news.bbc.co.uk/1/hi/sci/tech/8023413.stm">plenty of examples</a>. Some of the best documented are in <a href="http://www.sciencedirect.com/science/article/pii/0169534794900329">water striders</a> and <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3032.2008.00656.x/full">seed beetles</a>, but it has been reported from damselflies, diving beetles, bushcrickets, and many more. You could argue that <a href="https://theconversation.com/handcuffs-traps-and-spikes-shed-light-on-sex-lives-of-insects-26425">bushcrickets too</a> are an example of forced copulation.</p>
<p><strong>How can I identify insects?</strong></p>
<p>Some insects look positively ancient. If you have found an insect you are curious about identifying, I would say the first stop would be to send photos to the folks at <a href="http://www.bugguide.net">BugGuide</a> together with a description of where it was and what it was doing – they reply very quickly and will help to identify it. </p>
<p>In many cases if you would like it identified right down to its species level you’d sadly have to kill the specimen – but don’t do this until the experts say that’s necessary, as some species are recognisable from photos and locations.</p>
<p><strong>What insect has the weirdest shaped, um, equipment?</strong></p>
<p>I reckon you would have to go a long way to beat the <a href="http://phenomena.nationalgeographic.com/2012/10/25/to-find-out-why-this-beetle-has-a-spiky-penis-scientists-shaved-it-with-lasers/">seed beetles</a>. The gin-traps of the bushcrickets in our study do a good job, as does this <a href="http://maukamakai.wordpress.com/2010/03/08/shouldering-penis-extraction-in-rove-beetles/">rove beetle</a>.</p>
<p>Unfortunately researchers have typically made much more effort looking at male than female equipment – so it is hard to tell whether females usually have equivalently bizarre systems. I think my candidate for the weirdest system so far has to be <a href="http://phenomena.nationalgeographic.com/2014/04/17/in-this-insect-females-have-penises-and-males-have-vaginas/">this barklouse</a>, discovered only this year, where females have penis-like structures and males have vaginas, and females hold males down and scoop the sperm out of him over three days.</p>
<p><strong>Has monogamy ever been seen in insects?</strong></p>
<p>Yes, insect sex is not all crazy. Although, in animal terms, monogamy itself is pretty crazy in that it is extremely rare.</p>
<p>Termites are lifetime monogamous, with <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.1469-185X.1991.tb01136.x/abstract">a queen and a king</a>. Additionally, many ants are monogamous in that the queen is singly mated, although that was probably not the kind of monogamy you’re asking about.</p>
<p>There are also plenty of insects where the male sticks with the female for much, or even all, of the process of parental care. Burying beetles provide one well-studied example (in some cases), but males will often attempt to attract additional females, and the female will <a href="http://link.springer.com/article/10.1007%2FBF00176711">actively kick him over</a> to stop him producing the pheromones to do so! </p>
<p>The family Passalidae of dead-wood beetles are monogamous – the pair and their offspring form cooperative family groups in dead logs. There is a remarkable insect, a dung beetle <em>Cephalodesmius</em>, which lives in Australia. Males and females stay together throughout the provisioning period and the original paper proposed that they mate for life. This is probably because their form of parental care is particularly intensive – instead of collecting dung, they collects leaves and let them ferment into a ball of “homemade dung”. But this ball needs constant topping up and that is intense work, if you also have to defend the nest. Unfortunately this is a very poorly studied species and there are only really a few papers on it – and are not really widely available.</p>
<p><strong>Why do mantises eat the heads of their mates?</strong></p>
<p>It’s not immediately obvious what females get out of sexual cannibalism, but it could be a number of things. Males often make <a href="http://link.springer.com/article/10.1007%2Fs00442-009-1518-3?LI=true">poor-quality meals</a>, but in mantises, the hungrier a female is, the more she is <a href="http://beheco.oxfordjournals.org/content/19/4/710.full">likely to eat the male</a>. However, female orb spiders tend to attack everybody, and by doing so they can <a href="http://www.sciencedirect.com/science/article/pii/S0003347288802215">weed out the weaklings</a> and only mate with the strongest males. Finally some <a href="https://www.engr.colostate.edu/%7Eapruden/resume/Insect%20Behavior.pdf">female spiders kill males</a> whose attention just attracts predators and would endanger the female – after that, it doesn’t make sense not to eat him. But it seems mantises and spiders are particularly prone to sexual cannibalism, because their <a href="http://www.jstor.org/discover/10.1086/589518?uid=3737496&uid=2&uid=4&sid=21101310296827">sizes matter</a>. The smaller the males relative to the females, the more likely they are to be gobbled up. In mantises and spiders, females commonly dwarf males. </p>
<p><strong>Is there a fly that has a sperm which is 2.5 inches long?</strong></p>
<p>Yes, the fly is called <em>Drosophila bifurca</em> and produces 6cm sperm, more than 20 times the length of the male. Utterly incredible. The male produces only about 5 sperm per mating, which he feeds into the female until they snap. Producing such enormous sperm entails enormous testes, and the testes of a <em>D. bifurca</em> male can reach 11% of his body weight.</p><img src="https://counter.theconversation.com/content/27562/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Gilbert does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>The Conversation organised a public question-and-answer session on Reddit in which James Gilbert, postdoctoral researcher at the University of Sussex, explained weird and stunning insect reproductive strategies…James Gilbert, Postdoc in evolutionary insect ecology, University of SussexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/264252014-05-27T15:10:26Z2014-05-27T15:10:26ZHandcuffs, traps and spikes shed light on sex lives of insects<figure><img src="https://images.theconversation.com/files/49544/original/gm23zpqd-1401188147.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A male Mexican true bushcricket, left, grasps female with bear-trap genital claspers.</span> <span class="attribution"><span class="source">L Barrientos-Lozano</span></span></figcaption></figure><p>Handcuffs, spikes and traps – you would think they were part of some bondage aficionado’s bedroom collection. But what are they doing in the insect world?</p>
<p><a href="http://onlinelibrary.wiley.com/doi/10.1111/evo.12421/abstract">A new study</a> I worked on sheds light on why some bushcrickets – usually gentle creatures – get pretty violent when it comes to sex, and in the process helps to settle a decades-old debate about their odd mating habits.</p>
<p>In just a few species of bushcrickets, scattered across the evolutionary tree, we found that males have evolved horrific-looking clasping devices near their genitals. They use them to hold females down for as long as possible after sex is done – that is, after they have transferred all their sperm. This results in long mating sessions, up to seven hours in some cases.</p>
<p>Bushcricket claspers are usually simple feelers that engage with pits on the female. But some species use spiked hooks to grab onto the female, often piercing her cuticle. Others have bear-traps, tongs that wrap around her, or even interlocking “handcuffs” that completely encircle her.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=391&fit=crop&dpr=1 600w, https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=391&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=391&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=492&fit=crop&dpr=1 754w, https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=492&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/49270/original/nfttscfw-1400760502.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=492&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Male genital claspers from bushcrickets with relatively normal sex (left) and with protracted sex (right). In <em>Anonconotus</em> (top right) the spike pierces the female’s cuticle; in <em>Phasmodes</em> (bottom right) the interlocking claspers resemble ‘handcuffs’ and completely encircle the female.</span>
<span class="attribution"><span class="source">Karim Vahed</span></span>
</figcaption>
</figure>
<p>Females of these species are, perhaps understandably, not down with this. Although they themselves have not evolved any defensive tools, they actively resist by jumping, biting and kicking to dislodge the male – and with a degree of success, because species where females resist have less prolonged copulations than those where they do not.</p>
<p>Why would these males want to restrain their partners, when bushcricket mating is usually relatively peaceful? Female bushcrickets aren’t dangerous to males, unlike in some spiders where, before sex, males <a href="http://www.jstor.org/stable/4536229">gas females</a> or <a href="http://www.jstor.org/stable/3705799">tie them up in silk</a> to avoid being cannibalised. The answer takes us into one of evolution’s most important, but also most secretive, conflicts – the battle over what happens to sperm after mating – and also helps answer a longstanding question about some other odd sexual habits of bushcrickets.</p>
<h2>Sperm in a bag</h2>
<p><a href="http://press.princeton.edu/titles/7232.html">The act of mating itself is only the beginning</a> of a struggle to determine which male actually gets to fertilise the female’s eggs. One in which <a href="http://phenomena.nationalgeographic.com/2014/05/06/wheres-all-the-animal-vagina-research/">females play just as active a part as males</a>. </p>
<p>For example, female water striders have a submarine hatch covering their genitals, utterly preventing access. Unwanted males resort to “blackmailing” them into opening this hatch by <a href="http://www.nature.com/ncomms/journal/v1/n5/full/ncomms1051.html">threatening to attract predators</a>. Other female insects have <a href="http://motherboard.vice.com/read/the-labyrinthine-world-of-animal-genitals">labyrinth-like vaginas</a> with tortuous twists and blind endings. Some females even <a href="http://phenomena.nationalgeographic.com/2014/04/17/in-this-insect-females-have-penises-and-males-have-vaginas/">actively scoop sperm out of the male</a>. </p>
<p>In most land animals, however, we never actually get to see what happens next, because sperm is placed deep inside the female. Often we have to make guesses about what male and females do with their genitalia, based on their shape. But bushcrickets are ideal study animals to look at the evolutionary fate of sperm. </p>
<p>Male bushcrickets transfer all their sperm in a bag, which then drip-feeds into the female after the male has left. But female bushcrickets can, if they want to, get rid of unwanted males’ sperm by simply removing (and <a href="https://theconversation.com/if-size-and-frequency-count-crickets-may-be-the-sexiest-creatures-11691">usually eating</a>) the sperm bag before the sperm is completely transferred. Males would naturally rather this didn’t happen, and try to stop it. And because this happens outside the female’s body, we have an opportunity to watch what is going on.</p>
<h2>The food of love?</h2>
<p>If giving females sperm in a drip-feed bag isn’t weird enough, male bushcrickets normally also produce a giant sticky blob of gel from their genitals, which females proceed to eat. This “nuptial gift” is enormously costly to produce, weighing up to 40% of the male’s body weight. </p>
<p>(To be fair, it could be substantially worse for the male – in sagebrush crickets, for instance, females <a href="http://www.sciencedirect.com/science/article/pii/S0003347284711559/pdf?md5=e7ac7453474413ea2fa47cb1cfd52c37&pid=1-s2.0-S0003347284711559-main.pdf">suck the males’ blood</a> during sex and in striped ground crickets they <a href="http://www.jstor.org/stable/3496883">begin eating his legs</a>.)</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=404&fit=crop&dpr=1 600w, https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=404&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=404&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=508&fit=crop&dpr=1 754w, https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=508&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/49280/original/f2r7y3k4-1400764568.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=508&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Female bushcricket, <em>Poecilimon thessalicus</em>, feeding on a huge nuptial gift given to her by the male.</span>
<span class="attribution"><span class="source">Gerlind Lehmann</span></span>
</figcaption>
</figure>
<p>For decades, scientists have debated what this huge nuptial gift, or “spermatophylax”, is for. Some think that the gift is a nutritious meal that helps the female make more, better babies with the male sperm – a win-win situation that is <a href="http://www.scopus.com/record/display.url?eid=2-s2.0-0031935896&origin=inward&txGid=C5ECC5A91D0AABFF9D4ABC593CEAEF54.aXczxbyuHHiXgaIW6Ho7g%3a1">common in the insect world</a>. Especially when food is scarce, females can <a href="http://www.nature.com/nature/journal/v307/n5949/pdf/307361a0.pdf">use the gift as nutrition</a> for making offspring.</p>
<p>But others think that the nuptial gift is also a device for manipulation – ensuring the female is distracted, so the sperm bag gets to <a href="http://www.scopus.com/record/display.url?eid=2-s2.0-0001135320&origin=inward&txGid=C5ECC5A91D0AABFF9D4ABC593CEAEF54.aXczxbyuHHiXgaIW6Ho7g%3a8">drain as much sperm as possible</a> before she gets around to eating it. Gifts contain very poor nutrition – the equivalent of flavoured chewing gum – and are laced with substances that <a href="http://171.66.127.192/content/5/2/194.short">stimulate the female to feed</a> and also <a href="http://www.sciencedirect.com/science/article/pii/S0003347211004970">make her less likely to mate again afterwards</a>. </p>
<h2>Why bushcrickets get kinky</h2>
<p><a href="http://dx.doi.org/10.1111/evo.12421">Our new study</a> looks at some of the more bizarre mating habits of 44 species of bushcrickets to work out why in some cases males have resorted to more aggressive practices.</p>
<p>In a scattering of bushcricket species, we found that, over evolutionary time, males have stopped bothering to produce the nuptial gift for females at all. </p>
<p>In every case where the nuptial gift has been lost, males have evolved to protract sex for long periods even after they have transferred their sperm bag, attempting to restrain the female using hooks, tongs or handcuffs while she desperately resists. In cases where males present females with a food gift, though, the decision appears to be more mutual: females do not typically resist sex, and the males’ genital claspers fit neatly into special grooves on the female with no evidence for conflict.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=454&fit=crop&dpr=1 600w, https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=454&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=454&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=571&fit=crop&dpr=1 754w, https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=571&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/49271/original/j5jnrq7v-1400762116.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=571&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Mating pair of <em>Meconema</em> bushcrickets, female to the left, with male’s genital tongs highlighted in purple (and shown in inset).</span>
<span class="attribution"><span class="source">C. Roesti</span></span>
</figcaption>
</figure>
<p>Why do males of these species engage in such violent behaviour? We argue this almost certainly acts to prolong the drainage of sperm from the bag into the female for longer than she wants – the exact same function that had been proposed for the nuptial gift these species have lost. It is highly likely that this restraining behaviour is a substitute for the nuptial gift. </p>
<h2>It’s what you do with it that counts</h2>
<p>A great many studies of sexual conflict, especially spanning lots of species, <a href="http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001851">focus on the form and complexity of male genital structures</a> in particular – and there are <a href="http://maukamakai.wordpress.com/2010/03/08/shouldering-penis-extraction-in-rove-beetles/">certainly some corkers about</a>. </p>
<p>But our study shows that sexual conflicts don’t necessarily lead to more complex male genital structures. For example, bushcricket male claspers already had simple hooked “teeth” – which usually engage peacefully with pits on the female. Some of our “stingy” males, though, used these same teeth in a different way – holding the female forcefully, piercing her cuticle. Without observing the behaviour, this difference wouldn’t have been obvious.</p>
<p>There is also currently a prevailing view that <a href="http://www.sciencedirect.com/science/article/pii/S0003347211000510">females are passive</a> or possibly even <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1420-9101.2003.00506.x/full">willing recipients</a> of male attempts to manipulate them. Female genital structures are often not as varied as those of males, and <a href="http://onlinelibrary.wiley.com/doi/10.1111/j.0014-3820.2004.tb00482.x/abstract">some have pointed to this fact</a> as evidence that there really is no conflict going on. But our study clearly shows that, in this case, females actively and effectively resisted males using simple behaviour – jumping, biting and kicking – and not with specially evolved structures.</p>
<p>Whether you have gin-trap shaped genitals, a giant gift of jelly, or relatively normal-looking sexual apparatus, it is not what you have but what you do with it that counts.</p>
<hr>
<p><em>Next, read this: <a href="https://theconversation.com/invertebrates-inject-a-bit-of-romance-during-sex-by-stabbing-each-other-24154">Invertebrates inject a bit of romance during sex – by stabbing each other</a>.</em></p>
<p><em>James Gilbert will be doing a Reddit Ask Me Anything (AMA) on June 3 from 4pm to 6pm BST. Summaries of past AMAs are <a href="http://theconversation.com/topics/reddit-science-ama">here</a>.</em></p><img src="https://counter.theconversation.com/content/26425/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Gilbert receives funding from the European Commission’s Seventh Framework Programme.</span></em></p>Handcuffs, spikes and traps – you would think they were part of some bondage aficionado’s bedroom collection. But what are they doing in the insect world? A new study I worked on sheds light on why some…James Gilbert, Postdoc in evolutionary insect ecology, University of SussexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/241542014-03-11T06:18:03Z2014-03-11T06:18:03ZInvertebrates inject a bit of romance during sex – by stabbing each other<figure><img src="https://images.theconversation.com/files/43496/original/2yvv7pp6-1394463983.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Bedbug male stabbing a female during sex.</span> <span class="attribution"><span class="source">Wikimedia</span></span></figcaption></figure><p>It is fair to say we belong to a species obsessed by sex. We are among the only species to have <a href="http://www.goodreads.com/book/show/1991.Why_Is_Sex_Fun_The_Evolution_of_Human_Sexuality">sex for fun</a>, not just for reproduction. For some other species, though, sex is far from fun. In fact, as two recent review papers show, it is a war zone, involving penis fencing and love darts.</p>
<p>In 1897, the Italian zoologist Constantino Ribaga discovered a strange organ in female bedbugs, halfway up the abdomen. He suggested they used it to produce sound, like cicadas. But something wasn’t right: in the bundle of cells underneath this organ he found large quantities of sperm.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43494/original/ps6xf7ty-1394462791.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The organ discovered by Ribaga, later dubbed a spermalege.</span>
<span class="attribution"><span class="source">Rich Naylor</span></span>
</figcaption>
</figure>
<p>How did they get there? At the time, puzzled scientists concluded males must flood females with sperm, and the female digested the excess – as a “nuptial gift” – using this organ. But this theory was tenuous at best.</p>
<p>It wasn’t until 1913 that males were observed stabbing females through this organ with a horrifying syringe-like penis, then copulating with the wound. Sperm swim directly to the ovaries through the body cavity. This has been termed “traumatic insemination”.</p>
<p>In the first of the two papers, appearing in <a href="http://onlinelibrary.wiley.com/doi/10.1111/brv.12018/abstract">Biological Reviews</a>, Rolanda Lange and colleagues at Tuebingen in Germany and Sheffield in the UK show that similar behaviour occurs across invertebrates. </p>
<p>In snails, which are hermaphrodites, amorous advances involve “traumatic secretion transfer”, blasting potential mates at close range with <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1560308/">“love darts” covered in psychoactive mucus</a>. Understandably, neither party is keen to play the female role, involving being shot. In sea slugs this results in “<a href="http://euplotes.biology.uiowa.edu/web/sexpapers/2004/week3/penisfencing.pdf">penis fencing</a>” – each attempting to penis-stab the other. An inflicted wound inoculates the recipient with sperm.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=617&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=617&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=617&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=775&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=775&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43485/original/vs5dscmb-1394459583.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=775&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A brown garden snail (<em>Cantareus aspersus</em>) impales its mate with a “love dart”.</span>
<span class="attribution"><span class="source">Ronald Chase/Proceedings B</span></span>
</figcaption>
</figure>
<p>Why would a male want to impale the mother of his future children? In a paper in <a href="http://www.annualreviews.org/eprint/kaA4UnbT5FIwsSjtW5Wp/full/10.1146/annurev-ento-011613-162111">Annual Review of Entomology</a>, Nik Tatarnic and colleagues from Sydney in Australia and Sheffield in the UK focus on arthropods. They explain that stabbing is, in evolutionary terms, a game-changing tactic for males.</p>
<p>To sire offspring obviously requires mating, but this is only a prelude. Much more crucial is fertilisation, and females understandably want to control when, where and by whom their eggs are fertilised.</p>
<p>In many cases <a href="http://press.princeton.edu/titles/5817.html">females are highly successful at this</a> – by, for example, using their reproductive tract as a powerful tool to screen out all but preferred males. Females often simply <a href="http://www.nature.com/nature/journal/v405/n6788/full/405787a0.html">eject unattractive males’ sperm</a>, or <a href="http://www.researchgate.net/publication/257811739_Ejaculate-female_and_sperm-female_interactions/file/9c960525dfc396be0c.pdf">filter it out chemically,</a> and sometimes can <a href="http://www.sciencedaily.com/releases/2007/04/070430214515.htm">close their tract entirely</a>. Female control is especially widespread in insects, where females store sperm in a sac – sometimes for years, opening it to fertilise eggs at their leisure.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43487/original/m3m462qb-1394460823.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The dragonfly penis is shaped like a spade for removing rivals’ sperm.</span>
<span class="attribution"><span class="source">Jonathan Waage/Science</span></span>
</figcaption>
</figure>
<p>On the other hand, each male mating with a female would prefer his own sperm to fertilise the offspring. To achieve this, he must both overcome the female’s defences and beat her other mates – two neverending “arms races”. </p>
<p>Males can beat rivals to the first step – that is, mating – by impressing females through courtship. This may also <a href="http://rspb.royalsocietypublishing.org/content/267/1443/559.abstract">win favour at the fertilisation phase</a>. But males are more sneaky than that, with outlandish adaptations to ensure their sperm win the race, like <a href="http://link.springer.com/article/10.1023/A:1005596707591">plugging females up</a>, or <a href="http://www.jstor.org/stable/pdfplus/1747893.pdf">scooping out rival sperm</a>. Our own human organ may indeed have a <a href="http://www.fed.cuhk.edu.hk/%7Elchang/material/Evolutionary/Penis%20shape%20and%20sperm%20displacement.pdf">dual function as a “sperm scoop”</a>.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=516&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=516&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=516&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=648&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=648&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43488/original/9sfs3dwd-1394461050.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=648&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Wood mouse sperm form a snake by hooking on to each other.</span>
<span class="attribution"><span class="source">Harry Moore/ABC</span></span>
</figcaption>
</figure>
<p>Another solution is to try and directly overcome challenges posed by the females’ reproductive tract. Fruit fly males <a href="http://onlinelibrary.wiley.com/doi/10.1046/j.1365-2540.2001.00961.x/abstract?deniedAccessCustomisedMessage=&userIsAuthenticated=false">spike their sperm</a>, drugging females into releasing more eggs, even though this <a href="http://www.pnas.org/content/96/9/5083.short">shortens females’ lives</a>. Wood mice females produce mucus that only strong-swimming sperm can cross. Ever resourceful, males’ <a href="http://www.nature.com/nature/journal/v418/n6894/full/nature00832.html">sperm team up into long “snakes”</a> that, together, altruistically push one lucky sperm through the mucus to success.</p>
<h2>Stabbing for the win</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=362&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=362&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=362&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=454&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=454&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43493/original/76g8kd3j-1394462564.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=454&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Syringe-like bedbug paramere (penis), adapted for stabbing females.</span>
<span class="attribution"><span class="source">Cassandra Willyard/lastwordonnothing.com</span></span>
</figcaption>
</figure>
<p>Penis-stabbing, though, shifts the goalposts entirely. By injecting sperm directly into females’ body fluid, male bedbugs bypass the female’s adaptations to control access to her eggs. <a href="http://www.pnas.org/content/98/10/5683.full">The female is injured in the process</a>, reducing her number of offspring. But in the cold language of statistics, this may be worth it for the male – a healthy female is no good if she doesn’t bear his offspring. Males can both prevent females from excluding their sperm and also from preferring other males.</p>
<figure class="align-left zoomable">
<a href="https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43489/original/v4cphft9-1394461244.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The nightmarish embolus (penis-like organ) of a male <em>Harpactea sadistica</em> spider.</span>
<span class="attribution"><span class="source">Milan Rezac/Science Blogs</span></span>
</figcaption>
</figure>
<p>This has been such a successful strategy for males that it has evolved repeatedly across the animal kingdom. Male <em>Myzostoma</em> worms <a href="http://link.springer.com/article/10.1007%2FBF01632709">secrete corrosive enzymes from their penis</a>, dissolving a hole in the female’s skin into which they ejaculate. Male giant squid <a href="http://www.nytimes.com/1997/10/21/science/when-giant-squids-mate-it-s-a-stab-in-the-dark.html">inject sperm packets into females’ arms</a> – although occasionally they end up inseminating themselves, literally shooting themselves in the foot. In <em>Harpactea sadistica</em> spiders, the male bites the female, then <a href="http://scienceblogs.com/notrocketscience/2009/04/28/traumatic-insemination-male-spider-pierces-females-undersi/">stabs her with needle-like genitals</a>, ejaculating into the wound.</p>
<p>In some groups, like “bat bugs”, males spear females at random. In many others, though, females have evolved damage-limiting adaptations such as <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1691516/">the bedbug “spermalege”</a> (the organ discovered by Ribaga), offering an easy entry point to discourage indiscriminate stabbing. <a href="http://rsbl.royalsocietypublishing.org/content/2/1/58.abstract">Some species</a> have entire “paragenital systems” guiding sperm to their ovaries, while the regular reproductive apparatus shrivels from disuse.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/43491/original/2cdwjbhg-1394461861.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption"><em>Polistes</em> wasp infected with a female <em>Xenos</em> twisted-wing parasite. Her brood canal pokes out for prospective mates, who, mysteriously, often ignore it and stab her instead.</span>
<span class="attribution"><span class="source">Macro Photography/Aculeata Research</span></span>
</figcaption>
</figure>
<p>Males will often jump on and penis-stab anything that comes their way, even females of other species, often killing them in the process – a phenomenon that has <a href="https://theconversation.com/piercing-genitals-good-for-species-diversity-17897">driven some species to evolve apart</a>. Male bedbugs regularly jump other males by mistake – which is such a problem that males in one species have <a href="http://www.jstor.org/discover/10.1086/522844?uid=3738032&uid=2&uid=4&sid=21103692477673">evolved their own damage-control spermaleges</a>. </p>
<p>In an arms race, though, neither side can win – each can only gain a temporary advantage – and, as expected, females are fighting back. Astonishingly, some female bedbugs have evolved modified spermaleges that <a href="http://www.jstor.org/discover/10.1086/522844?uid=3738032&uid=2&uid=4&sid=21103692477673">mimic those of males</a>, to reduce harassment. Others have evolved ways of <a href="http://www.pnas.org/content/106/51/21743.abstract">digesting the injected sperm</a> and using it to repair their wounds, minimising the damage.</p>
<p>The course of true love never did run smooth. For males and females locked in an arms race, though, it could be said to run in circles – vicious ones at that. And all to inject a little bit of romance.</p><img src="https://counter.theconversation.com/content/24154/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>James Gilbert receives funding from the European Commission’s Seventh Framework Programme. </span></em></p>It is fair to say we belong to a species obsessed by sex. We are among the only species to have sex for fun, not just for reproduction. For some other species, though, sex is far from fun. In fact, as…James Gilbert, Postdoc in evolutionary insect ecology, University of SussexLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/201752013-11-13T06:12:48Z2013-11-13T06:12:48ZHead-butting did not lure mates for horny-domed dinosaur<figure><img src="https://images.theconversation.com/files/35035/original/czhqvqd6-1384268794.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">For glory, not sex.</span> <span class="attribution"><span class="source">PLOS</span></span></figcaption></figure><p>Pachycephalosaurus is famous for its appearance in the movie Jurassic Park: The Lost World, where one is shown battering a man and his car. To achieve the feat the dinosaur used its greatly-thickened skull, which is one of its unique features. But for many years there has been a feud between researchers about the real-life role of this skull.</p>
<p>The dome-shaped skull is often decorated with knobs and spikes, which made some researchers think that the skull of pachycephalosaurs was for some sort of sexual display. But now, in a new study published in <a href="http://dx.doi.org/10.1371/journal.pone.0068620">PLOS ONE</a>, researchers have shown that pachycephalosaurs were into head-butting far before Zinedine Zidane. They used it as a weapon against rivals.</p>
<p>To work out whether pachycephalosaur skulls were for lovers or fighters, Joseph Peterson of the University of Wisconsin looked at the “wounds” of specimens recovered from palaeontological digsites. He found that more than 20% showed signs of having suffered from combat. More interestingly, most of the wounds appeared at the top of the skull. This bit of the skull could only have been used so often if it was used as a weapon. This pattern is seen across most of the 14 analysed species in a decent sample-size of 109 skulls.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=957&fit=crop&dpr=1 600w, https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=957&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=957&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1203&fit=crop&dpr=1 754w, https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1203&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/35034/original/ss3whm7q-1384268638.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1203&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Using that head for good.</span>
<span class="attribution"><span class="source">PLOS</span></span>
</figcaption>
</figure>
<p>There is a possibility that these “wound marks” were caused after the animal had died, for example by getting hit by pebbles in a river. But Peterson published <a href="http://www.bioone.org/doi/abs/10.2110/palo.2013.p13-003r">another study</a> testing this hyphothesis using a method called “experimental taphonomy”. The idea is to reconstruct the post-mortem activities that might have influenced an animals’ transformation into a fossil. This also involves factoring processes like tissue degradation.</p>
<p>Peterson created several casts of pachycephalosaur skulls of almost identical density and consistency as bone. He then plopped them in a flume which can mimic the flow of water and sediments within a stream. They found that the skull domes landed either on their top or bottom surfaces. If erosional damage did leave marks, you would expect to find scars on both sides of the skull. But that wasn’t the case with the skulls Peterson used for the analysis.</p>
<p>Such traumatic scars are arguably more value than the fossils they are scorched onto. Whereas a standard bone tells us about when an animal died, the traces left behind on these, such as bite marks or other combat wounds, give us an insight into the behaviour of animals that have been dead for 66 million years.</p>
<p>It also shows that palaeontology is a lot like trying to solve a rubik’s cube – we have a jumble of information, which needs to be solved to give us the story. In the process we are led down different paths or interpretations of that data – and sometimes we need to go backwards. But there are times when exquisite and rare fossils, and their accompanying studies such as this, give us a completed face to continue forward and discover ever more. Maybe one day we’ll be able to solve the cube.</p><img src="https://counter.theconversation.com/content/20175/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Jon Tennant receives funding from NERC</span></em></p>Pachycephalosaurus is famous for its appearance in the movie Jurassic Park: The Lost World, where one is shown battering a man and his car. To achieve the feat the dinosaur used its greatly-thickened skull…Jon Tennant, PhD student, Imperial College LondonLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/178522013-09-09T05:39:58Z2013-09-09T05:39:58ZGuppies lie about mate choice to trick rivals<figure><img src="https://images.theconversation.com/files/30697/original/73dzgdbt-1378285111.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Is he leading her on?</span> <span class="attribution"><span class="source">orkomedix</span></span></figcaption></figure><p>When it comes to sex among guppies, competition is high for those at the top of the game. To get around this predicament, <a href="http://f1000research.com/articles/2-75/v2">a recent study</a> has shown, guppies use trickery. </p>
<p>Competition in fish of the Poeciliidae family (fresh-water fish to which guppies belong) is especially intense, because members of the species commonly mimic each others’ choices. This creates a conundrum: what to do when everyone wants the same mate?</p>
<p>Poeciliids also experience significant <a href="https://theconversation.com/fathered-by-the-dead-guppies-push-the-extremes-of-reproduction-16289">sperm competition</a>. After copulation, females can store sperm to use later, meaning that sperm from multiple males co-exist and compete within the female’s body. </p>
<p>There is evidence that more recently injected sperm is more likely to be used to fertilise eggs. Thus, a male poeciliid has a very good reason to lead other males away from his preferred female. If he can prevent — or even delay — her copulation with another male, then he can improve his odds of fathering her offspring. </p>
<p>Poeciliids are known to mimic each other’s mate choices, which means that by the very act of copulating with his first-choice mate, a male may have encouraged his rivals to do the same. It is a poeciliid predicament.</p>
<p>One way to get around this is to fake it. If you are vigilant about when others are observing and imitating your choices, then you can act as though you prefer X, even when you actually prefer Y. This will make others eager to obtain X as well, leaving you with Y all to your manipulative self.</p>
<p>If a male fish were especially successful at this form of trickery, he could mate with his preferred female first, then turn around and mate with a different, less desirable one, to try to divert the attention of rival males away from his first choice. A little bit of deception could go a long way when it comes to avoiding sperm competition.</p>
<p>David Bierbach and colleagues at the University of Frankfurt designed a study to test this hypothesis. They conducted experiments to determine whether the more sexually active species - the ones most likely to have mating systems involving sperm competition — were more likely to change their mate preference when they had an “audience” of another sexually mature male. They obtained data from ten types of poeciliid fish. </p>
<p>The researchers determined whether male sexual activity and aggression was consistent within species, and also whether behaviour differed between species. Next, they tested to see whether more sexually active species were more aggressive than less sexually active species. Finally, they compared the magnitude of “audience-induced” changes in mate choice across species. </p>
<p>Then, the ultimate question: if there are differences in deceptive mate choice between species, are the more deceptive species also the more sexually active and aggressive species, as hypothesised?</p>
<p>To understand the answer to that question, we need to step back. Deceptive mate-choice behaviour may not be entirely explained by sperm competition. It could be that a male is trying to avoid an aggressive encounter with another male by selecting non-preferred females when rivals are around. He may be more of a wimp than a trickster. This is why Bierbach also tested whether a species’ level of male aggression was correlated to sexual activity and audience effects in mate choice.</p>
<p>Bierbach’s results are best summarised in the title of the journal article: “Casanovas are liars”. The results indicate that male poeciliids are indeed tricksters: males showed significant “audience effects” in nine of the ten species that were tested. There was a positive correlation between level of sexual activity and the likelihood that a male fish would show audience effects in his mate choices. However, the analyses show correlation, not causation. Every reason to keep studying guppy sex.</p><img src="https://counter.theconversation.com/content/17852/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Anne-Marie Hodge does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>When it comes to sex among guppies, competition is high for those at the top of the game. To get around this predicament, a recent study has shown, guppies use trickery. Competition in fish of the Poeciliidae…Anne-Marie Hodge, PhD student, University of WyomingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/162892013-07-25T05:06:57Z2013-07-25T05:06:57ZFathered by the dead: Guppies push the extremes of reproduction<figure><img src="https://images.theconversation.com/files/27915/original/4jjz8qwg-1374568723.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Where is my dad, mum?</span> <span class="attribution"><span class="source">Alice Chaos</span></span></figcaption></figure><p>All organisms have been evolutionary programmed to spread their genes as far and wide as possible. One way to do that is to produce many offspring, and for that animals have developed some very strange tactics of reproduction. </p>
<p>For instance, the [Antechinus], a tiny marsupial carnivore, has a “live fast and die young” pattern (also known as “<a href="http://www.abc.net.au/science/articles/2011/07/07/3262428.htm">big bang reproduction</a>”) in which the males mate for two weeks straight. In the process, they bring themselves to such a state of exhaustion that their immune system fails, and they die. This behaviour may seem like a rather unwise choice, but it seems to work for them …</p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=449&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=449&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=449&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=565&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=565&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27844/original/jrqjwz4s-1374510857.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=565&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Agile antechinus.</span>
<span class="attribution"><span class="source">Wikipedia</span></span>
</figcaption>
</figure>
<p>The Trinidadian guppy has found an even stranger way - by fathering offspring after death. In a recent paper in the journal <a href="http://dx.doi.org/10.1098/rspb.2013.1116">Proceedings of the Royal Society B</a>, David Reznick of the University of Pennsylvania reports that female Trinidadian guppies (<em>Poecilia reticulata</em>) can store sperm from a male and continue to use it to fertilise eggs for generations even after the male’s demise.</p>
<p>Reznick has been studying Trinidadian guppies <a href="http://cnas.ucr.edu/guppy/">for many years</a>. The species exhibits rapid evolutionary responses, making it a great model for answering questions that evolutionary biologists are interested in.</p>
<p><a href="http://dx.doi.org/10.1016/0300-9629(78)90200-1">Earlier research</a> showed that female guppies have special adaptations for storing and nourishing sperm after they mate. Lab experiments showed that these females can reproduce long after they have been removed from the presence of males. Also, Trinidadian guppies exhibit a large difference in lifespan between the sexes. Female lifespans can actually stretch over several male generations — they may survive up to two years, in contrast to just three to four months for the males.</p>
<p>All this raises an interesting question: given the sperm storage capabilities of females, and the fact that they outlive males by a wide margin, is it possible that some sperm is technically fertilising eggs and producing offspring after the father himself is dead? </p>
<p>The data for the recent study came from a set of guppies that had recently been introduced to a stretch of the Lower LaLaja tributary in Trinidad’s Northern Mountain Range. The researchers put the guppies in tanks to mate, then released them into a contained tributary. They returned at regular intervals to capture the guppies and collect both demographic information and DNA samples.</p>
<p>When it became apparent that there were more fathers producing offspring than there were reproductive males in the population, the team decided to analyse the demographic and genetic data to answer several questions: whether posthumous reproduction was occurring, and just how common it might be, relative to “traditional” reproduction (that is, fertilisation with the gametes of two living animals). This was a perfect opportunity for such a study, because the animals were already individually marked and had known pedigrees.</p>
<h2>Strange sex lives</h2>
<p>The results confirmed the researchers’ hypothesis about posthumous reproduction. They found that there were indeed some males producing new offspring long after they had disappeared from the population. </p>
<p>Because only unmated juveniles were initially included in the introduction, the population started out with zero “dead reproductives” (males producing offspring after disappearing from the population), but the number of dead reproductives gradually increased as time passed. The proportion of dead males that remained reproductively active maxed out at about 25% of the total population. The individual male guppies may have been gone, but their sperm was getting along just fine in their absence.</p>
<p>Out of the 278 male guppies included in the study, just over half had at least one successful reproductive event. Only about half of those that successfully reproduced did so only while they were alive. Another third reproduced both before and after their deaths, and a persevering 15% managed to reproduce only after their demise. So it turns out that being dead is not necessarily a barrier to successful reproduction for these guppies. But why? And what does this tell us about guppy ecology?</p>
<h2>Why do it, dad?</h2>
<p>Guppy mortality patterns show extreme seasonal spikes for males, with a sharp rise in mortality during the wettest months of the year (July to November). The the females make up for this by acting as living arks for the males’ genes. They essentially act as swimming seed banks: protecting the delicate gametes from challenging conditions and releasing them later, when the environment is more hospitable.</p>
<p>Reznick point out that as long as sperm is stored inside a female guppy’s body, it is essentially “shielded” from selection. This allows the persistence of adaptations that may not necessarily be useful at a given time, but could prove to be valuable for increasing genetic diversity at some point in the future.</p>
<p>This reproductive pattern could have profound benefits for a species that often exists in small, isolated populations. If females are carrying the sperm from previous partners, this can increase both the diversity of gametes available and the <a href="http://www.uwyo.edu/dbmcd/molmark/lect07/lect7.html">effective population size</a>. More genetic diversity will <a href="http://evolution.berkeley.edu/evosite/evo101/IIID3Bottlenecks.shtml">relieve risk the risk of genetic bottlenecks</a>, which frequently plague small, isolated populations. Also, this study lasted less than a year. Female guppies may store sperm for even longer than is reflected by the present data.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/27916/original/3yxwczqk-1374569777.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Fancy those colours?</span>
<span class="attribution"><span class="source">thefixer</span></span>
</figcaption>
</figure>
<p>Sperm storage may also allow female guppies to produce sons that are more attractive to other females. Previous research has shown that guppies exhibit a variety of colour polymorphisms, and that females tend to prefer males exhibiting <a href="http://dx.doi.org/10.1006/anbe.1999.1225">rarer colour patterns</a>. If a mother guppy can mate with a male of a particular colour, there is a chance that by several male generations down the line that colour pattern will be rare or non-existent. When the female guppy finally uses her banked sperm, she will have an exotic looking son that should be highly preferred by other females. Having a popular son is beneficial to both males and females, as it means that their genes are more likely to be carried into future generations. </p>
<p>This also creates an unusual situation: males may face competition both within their own cohort and with older males that may have died before the current crop of suitors had even hatched. There is some evidence for “last-male precedence” (fresher sperm being preferred for fertilisation), which gives an advantage to the young guys, but they cannot entirely escape the fact that their predecessors’ sperm is still on the market.</p>
<p>The implications of this discovery are noteworthy. The study unveils a new mechanism that animals can use to maintain genetic diversity, and shows that male reproductive fitness may not necessarily depend upon long-term survival. The news should also spur researchers to take a second look at other animals that are known to store sperm, such as <a href="http://www.livescience.com/37782-animal-sex-how-ants-do-it.html">ants</a>, <a href="http://dx.doi.org/10.1007/s00040-003-0641-0">bees</a>, <a href="http://io9.com/5626348/female-whale-sharks-may-have-a-built+in-sperm-bank">sharks</a> and even <a href="http://dx.doi.org/10.1016/j.ygcen.2009.06.012">bats</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/W4KR4oK8nDc?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
</figure>
<hr>
<p><em>This an edited version of a post that was first published on <a href="http://www.scilogs.com/endless_forms/2013/07/16/deadbeat-dads-first-evidence-of-posthumous-reproduction/">Anne-Marie Hodge’s blog</a>.</em></p><img src="https://counter.theconversation.com/content/16289/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>There are no potential conflicts between the author of this article and any parties related to the research being reported or the journal in which the study was published.</span></em></p>All organisms have been evolutionary programmed to spread their genes as far and wide as possible. One way to do that is to produce many offspring, and for that animals have developed some very strange…Anne-Marie Hodge, PhD student, University of WyomingLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/116912013-01-18T05:23:28Z2013-01-18T05:23:28ZIf size and frequency count, crickets may be the sexiest creatures<figure><img src="https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">crickets Mormon Tom Zegler</span> </figcaption></figure><figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=450&fit=crop&dpr=1 600w, https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=450&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=450&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=566&fit=crop&dpr=1 754w, https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=566&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/19379/original/j446dn4f-1358486472.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=566&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Life as a cricket is rough: cannibalism, exhausting procreation and the world’s largest testicles.</span>
<span class="attribution"><span class="source">Tom Zegler</span></span>
</figcaption>
</figure>
<p>If you had to guess what creature in the world had the largest testes, I doubt you would guess that the prize belonged to a cricket.</p>
<p>The <a href="http://www.abc.net.au/science/articles/2010/11/10/3062584.htm">testes of the tuberous bush cricket</a> (<em>Platycleis affinis</em>) are an internal affair, taking up most of the cricket’s abdomen. At nearly 14% of their body weight, they are disproportionately large when compared to other species. Just think, a 100kg human would be walking around with 14kg of testicles, which would be mighty uncomfortable.</p>
<p>Why do these crickets need all that sperm power? It is because their females are highly promiscuous. The male bush crickets do not release more sperm than normal in any given sexual act, but they can be called upon to do it so often they apparently need the reserves. In the world of insects, it is not worth missing an opportunity, and if the females are going to be all available like that, then a cricket needs some world-class balls.</p>
<p>But this is not the only sexual record held by crickets. An Australian species known as scaly crickets (<em>Ornebius aperta</em>) have <a href="http://www.abc.net.au/science/articles/2010/11/10/3062584.htm">the most frequent sex</a> of any species in the world. These little guys can do it more than 50 times in a few hours, often with the same female! </p>
<p>Why do they have to keep this up? Because she eats it.</p>
<p>That’s right, cricket sex provides more than the spark for the next generation. Males actually produce a package called a spermatophore, which is sperm wrapped up in a nutritious protein package. When the males insert it into a special opening in the females, sometimes she just bends down to gobble up her yummy post-coital snack.</p>
<p>Australian spiny cricket males respond to this sabotage by releasing only a few sperm per package, between 5 and 225 sperm per copulation, an astonishingly low amount compared to the average (100,000). Yet when researchers measured sperm loads in females, they had up to 20,000 sperm stored away. This means that they had sex up to 200 times to collect that amount.</p>
<p>Of course the females were storing up more than sperm. They also gathered nutrients that will help them develop eggs for the next generation. Other species of crickets manage the situation by offering a <a href="http://www.abc.net.au/science/articles/2004/05/12/1106630.htm">courtship gift</a> in the form of food from the dorsal glands that distract the female and give her something to eat during sex.</p>
<p>Some female crickets seek out males in order to get these tasty gifts. A <a href="http://www.livescience.com/16262-female-cricket-mating-food.html">study of 32 different species of bushcrickets</a> showed that the larger the spermatophore, the more likely the females were to actively seek out males. These gifts are costly to produce, so species that produce small spermatophores may mate twice a night, while those with large spermatophores may mate only once or twice in a lifetime.</p>
<p>The final cricket sex record goes to the <a href="http://en.wikipedia.org/wiki/Mormon_cricket">Mormon cricket</a>, which produces a spermatophore that is 27% of its body weight. That’s a huge investment in wild oats, which is a good description, since most of the package is food. The Mormon crickets are flightless and form swarms similar to locusts. These great walking hordes are often so hungry that cannibalism is common.</p>
<p>Female Mormon crickets will compete for males just so they can get a feed, and the benefit for the male is that some of his sperm may make it to the next generation.</p>
<p>Crickets are not likely to be overly loyal to each other, because <a href="http://news.sciencemag.org/sciencenow/2010/06/sex-and-the-crickets.html">research on Spanish field crickets</a> shows that individuals with more mating partners leave more offspring. This applies to both male and female crickets, so it is surprising that males will nevertheless protect a female that they have mated with.</p>
<p>Male crickets will linger near a female they have recently given their sperm to, not to scare away other suitors, but to <a href="http://www.nytimes.com/2011/10/11/science/11cricket.html/">protect the female from predators</a>. He does this at his own peril, because males that hang about after sex are four times more likely to be eaten. On the other hand, the females are six times less likely to be eaten if he is there to protect her.</p>
<p>Male crickets are not confused about the goal of spermatophore transfer. But female crickets want more than just sperm from their partner. A meal (or several dozen meals) increases the male cricket’s chance of getting lucky.</p>
<p>Maybe they are not so different from people, after all. </p><img src="https://counter.theconversation.com/content/11691/count.gif" alt="The Conversation" width="1" height="1" />
If you had to guess what creature in the world had the largest testes, I doubt you would guess that the prize belonged to a cricket. The testes of the tuberous bush cricket (Platycleis affinis) are an…Susan Lawler, Head of Department, Department of Environmental Management & Ecology, La Trobe UniversityLicensed as Creative Commons – attribution, no derivatives.