Males produce faster sperm when mated to their sisters, according to a recent study of guppies.
Researchers from the University of Western Australia paired male guppies (Poecilia reticulata) with either their sisters or with unrelated females. Males recognised their sisters and responded with fewer courtship behaviours, an expected result given the problems associated with inbreeding.
However, males paired with their sisters also produced faster sperm, an adaptation that may give them a competitive mating advantage over unrelated males.
Researcher John Evans speculates that this seemingly contradictory behaviour could be a form of sexual conflict. Both sexes prefer to avoid inbreeding, but males may be more tolerant when no other options are available. Producing faster sperm would therefore allow them to counteract the females’ preferences against sibling mating.Read more at University of Western Australia