Bizarre Squid Sex Techniques Revealed

James Owen
for National Geographic News
December 22, 2008
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.

Alternatively, it may be that waterborne residues from human contraceptive pills or other "gender-bending" pollutants known to be affecting fish and amphibians are also harming the squid, Hoving said.

(Related news: "Sex-Changing Chemicals Found in Potomac River" [January 22, 2007].)

Previous studies have suggested "contaminating chemicals are slowly getting into the deep-sea food web," Hoving noted.

Evolution Novelty

Another surprise was the first recorded case of a squid that fertilizes its eggs internally.

In a still largely mysterious process, female squid are generally thought to release their eggs into the water to be fertilized by sperm left on their bodies by males.

But females of the mini-squid Heteroteuthis dispar were found to have an internal sperm storage sac that connects to the oviducts, the tubes through which eggs pass.

"Spawning and fertilization is usually external in squid, but this species suggests it can happen internally," Hoving said. "The sperm is able to migrate toward the eggs before they leave the body."

Squid expert Vladimir Laptikhovsky, a government fisheries scientist for the Falkland Islands, described the find as "an outstanding discovery."

Laptikhovsky, who collaborated with Hoving on related studies, said that "internal fertilization occurs in octopods, but in squids … it is the first time [this has been recorded]. Nobody could expect such an evolutionary novelty."

Mike Vecchione of the Smithsonian's National Museum of Natural History in Washington, D.C., called the internal fertilization find "remarkable."

The discovery of male squid with female characteristics is also "completely new," he said.

Strange reproductive strategies are often seen among deep-sea creatures, Vecchione noted.

"For instance, there are angler fishes where the males are basically parasitic on the female. The male sniffs out the female and then bites her, and then turns into a parasitic bag of sperm," he said.

"The deep sea is an alien environment that's huge and very diffuse," he added, "so finding a mate and sticking with her until fertilization occurs is a challenge."

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