“Squid Males “Bisexual”—Evolved Shot-in-the-Dark Mating Strategy Mating with anything with eight arms pays off in dim depths, study says.”

A female O. deletron squid carrying sperm packets—seen as white dots—in 2007. Photograph courtesy MBARI

Traci Watson

for National Geographic News

Published September 20, 2011

When it comes to mating, some male squid aren’t very picky: They copulate just as often with other males as with females, a new study says.

That’s because would-be suitors of the hand-size species Octopoteuthis deletron, which live in the murky depths of the eastern Pacific Ocean, can’t easily tell the males from the females, the research shows.

“They can see each other, but they are not able very well to distinguish between the sexes at the distance at which they decide, ‘I’m going to mate’ or ‘I’m not going to mate,'” said study leader Hendrik Hoving, of the Monterey Bay Aquarium Research Institute in California.

So “males mate with basically any member of the same species. … They just take a chance.”

It’s also hard to tell he from she: A female squid’s defining feature is a patch of wrinkled skin.

The result is a strategy that the study authors call “a shot in the dark”—it’s just not worth it to males to make sure their partner is the right gender.

Same-Sex Mating Rare in Nature

For the study, Hoving and colleagues recorded squid via robotic submarines in the dark, 1,300 to 2,600 feet (400 to 800 meters) underwater. The scientists observed more than a hundred male and female squid, and found that just as many male squids as female squid bore sperm packets on their bodies—showing that males slap a sperm packet on just about anything with eight arms.

After courting, the male uses his large penis to transfer multiple sperm packets into the female through an opening in her mantle—or the main part of her body—as well as her arm tissue.

But the “love affair” ends there: The squid, which lead a solitary existence, die shortly after mating.

Nathan Bailey, of the U.K.’s University of St. Andrews, said the study team “makes a pretty good case” for their claims about the male squid’s lack of choosiness.

Very few species show such high levels of what biologists call same-sex sexual behavior, Bailey, who wasn’t involved in the research, said by email. “Some primates or dolphins do, but this study puts O. deletron on the higher end of the scale.”

Hoving acknowledged that his research results can become fodder for jokes.

“But I don’t really care,” he said. “I’m interested in deep-sea animals and how they’re capable of living in that environment, and one of the challenges is finding the opposite sex.”

The study appears in this week’s issue of the journal Biology Letters.


The white dots on this female Octopoteuthis deletron are embedded sperm. Males are often recipients of these rocket sperm.

Amorous Squid Seeks Partner: Any Sex Will Do

Published: September 20, 2011

A five-and-a-half-inch deep-sea squid that lives a solitary life up to half a mile down in the dark waters of the Pacific Ocean is the latest addition to the hundreds of species that are known to engage in same-sex sex

Over the years, scientists have added one creature after another to the list, making it clear that although nature may abhor a vacuum, it seems to be fine with just about everything else.

Male squid, for example, pay no attention to the sex of other squid. Understandably so. They live alone in the dark, males and females are hard to tell apart, and only occasionally do squids pass in the night. Far better to risk wasting a few million sperm than to miss out on a chance to reproduce.

This is only one among many sorts of same-sex sexual behavior. In some insect species, males engage in traumatic insemination, which is just what it sounds like, of other males and females alike. Among mammals, bottlenose dolphins and bonobos engage in lots of different kinds of sex. Male dolphins pursue sex with males and females equally, but the females show a preference for males. Bonobos pair off in all the combinations, often.

Laysan albatrosses form long-term female/female pair bonds, but for them the point is raising chicks, not sex. If one female can arrange a quick liaison with a male from another pair, the two females will tend the young. Noah might well have had two female albatrosses on the ark.

But for sheer amazement, the mating behavior of the squid, Octopoteuthis deletron, has to rank near the top. And the same-sex part is the least of it.

For the record, Octopoteuthis is the first among the spineless masses of invertebrates known to mate equally with males and females, Hendrik J.T. Hoving and two colleagues report in their paper, “A shot in the dark: same-sex sexual behavior in a deep-sea squid,” published, lurid title and all, in Proceedings of the Royal Society: Biology Letters. No surprise given its life in the deep.

The way the squid mate is something else. Little is known about the details but it seems that the male ejaculates a packet of sperm at the mating partner, and the packet turns inside out, essentially shooting the sperm contained in a membrane into the flesh of the partner, where they stay embedded until the female (if the shooter has been lucky) is ready to fertilize its eggs. If males are the recipient of these rocket sperm, they are just stuck with them. It is the kind of mating that would make a good video game.

And the visible evidence of those embedded sperm is what allowed Dr. Hoving and his co-authors to document the squid’s mating choices. They pored over video recordings acquired during almost 20 years of dives by remotely operated vehicles sent out by theMonterey Bay Aquarium Research Institute, where Dr. Hoving is doing research, to the deep Monterey Canyon off California.

One hundred and eight individual squid had been captured on video, and of that number the scientists could determine the sex of 39 of them: 19 females and 20 males. The equal numbers of males and females suggested that the sample was representative. So when they found that of these 39, 9 males and 10 females had embedded sperm — roughly equal numbers — they concluded that males were trying to mate equally with other males and females.

Dr. Hoving, who was leaving for research at sea himself around publication time for his paper, was prepared for attention to the same-sex behavior and was ready for people to conflate squid and human behavior and announce the discovery of gay squid.

He fended off that notion, reiterating that the squid has no discernible sexual orientation, and that a tentacled invertebrate that shoots sperm into its mate’s flesh really has nothing to do with human behavior.

Marlene Zuk, author of the newly published “Sex on Six Legs: Lessons on Life, Love, and Language from the Insect World,” and a biologist at the University of California, Riverside, agreed. She has written about the evolution of same-sex sex in a variety of insects and other animals, and she added a further caution.

Don’t imagine that squid are stupid, Ms. Zuk said, at least about being squid. “The animal is not making a mistake. It’s not mistaken to deposit sperm with another male,” because somehow, the behavior works, or natural selection would have eradicated the behavior or the squid.

And, she said, “we still have squid.”


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