for National Geographic News
A new investigation into the tangled sex lives of deep-sea squid has uncovered a range of bizarre mating techniques.
The cephalopods' intimate encounters include cutting holes into their partners for sex, swapping genders, and deploying flesh-burrowing sperm.
These and other previously unknown reproductive strategies were documented in a survey of ten squid species living worldwide at depths of between 984 and 3,937 feet (300 and 1,200 meters).
Study leader Henk-Jan Hoving, a Ph.D. student at the University of Groningen in the Netherlands, examined squid caught during research voyages as well as preserved museum specimens.
Cutting and Burrowing
Hoving's findings suggest males of the bioluminescent species Taningia danae use their beaks and sharp claws to slice two-inch-deep (five-centimeter-deep) wounds into their partners.
Sperm packets, or spermatophores, are then inserted into the female's cuts using a penis-like appendage, according to Hoving.
Meanwhile, males of the species Moroteuthis ingens were found to have sperm packets that, once deposited onto a female, burrow into the body.
"The spermatophores penetrate the skin independently," Hoving said. "They probably do that with the help of an enzyme-like substance that dissolves tissue."
The study also identified the first known transgender squid: Ancistrocheirus lesueurii.
Some males of this species studied for the survey not only resembled the opposite sex in size and appearance but were found to have developed female sex glands.
One possible explanation is that the males impersonate females to sneak undetected among potential mates, Hoving said.
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