In a form of imposed contraception, some arrow squid males prevent their female consorts from fertilizing their eggs with another male’s sperm.
Arrow squid aren’t particularly loyal. Females mate with several males and can even store the sperm from such liaisons in special receptacles for future use. New research led by Luiza Saad, a doctoral candidate in zoology at the University of São Paulo in Brazil, however, shows that certain males have evolved a strategy to get ahead of the competition: they lodge a tube-like plug into the female’s reproductive tract, blocking her ability to use stored sperm.
Joshua Rapp Learn 