Image: Female Octopoteuthis deletron
©2007 MBARI
A female Octopoteuthis deletron in the water column observed by MBARI’s remotely operated vehicle Ventana in December 2007. The photophores on the arm tips are visible.
By Senior writer
updated 9/20/2011 8:50:44 PM ET 2011-09-21T00:50:44

Meeting girls is tough if you're a male squid living in the deep, dark waters off the coast of California. You may run across your own species only rarely — and when you do, the deep-sea gloom makes it hard to tell whether your new pal is a guy or gal.

But one squid species has come up with a work-around to this matchmaking problem, a new study finds. The eight-armed lotharios simply mate with any squid of their species that crosses their path. If that means wasting some sperm on male-to-male matings, the squid don't seem to mind.

This same-sex squid behavior can't necessarily be taken as more evidence of homosexual bonding in the wild, according to study researcher Henk-Jan Hoving, a postdoctoral researcher at the Monterey Bay Aquarium Research Institute in Moss Landing, Calif. Rather, the squid seem to mate indiscriminately out of necessity.

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"In addition to the dark habitat the animals live in, the animals only reproduce once, encounters with partners are few and far between, and mating is probably rapid," Hoving wrote in an email to LiveScience from a research vessel off the U.S. West Coast. "We think the high frequency of male matings is the result of a combination of all the above factors." [ Top 10 Swingers of the Animal Kingdom ]

Same-sex squid
The squid in question, Octopoteuthis deletron, is a medium-size creature whose body can grow to about 6.5 inches long. Little is known about the squid's life cycle, because O. deletron is relatively rare, and its deep-sea habitat hardly invites observation.

But by using remotely operated vehicles, scientists were able to capture images of 108 O. deletron squid in the Monterey Submarine Canyon off California's coast between 1992 and 2011. The squid were cruising waters from 1,300 to about 2,600 feet deep.

For many of the animals, the footage wasn't clear enough to determine the squid's sex. But 39 of the squid could be sorted into male and female. It was here that Hoving and his colleagues made a curious discovery: The same number of male and female squid showed evidence of a recent amorous run-in with a male. [ See images of squid ]

This evidence took the shape of spermatangia, little sacs of sperm that male squid deposit onto the female during mating. These packets inject sperm into the female's body. The packaging remains attached to her skin, signaling she has mated recently.

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Males were just as likely to be found sprinkled with empty spermatangia packets as females, the researchers reported Sept. 20 in the journal Biology Letters. Nine males and 10 females had spermatangia packets dotting their bodies.

Mysterious squid
The packets were placed in areas out of the reach of the males' own penises, suggesting they hadn't accidentally inseminated themselves. More likely, Hoving and his colleagues wrote, is that it's simply less costly for squid to waste some sperm on same-sex mating than it is to evolve elaborate courtship behavior to pick out fertile females.

The squid live solitary lives, Hoving and his colleagues wrote, and may run into members of their species only rarely. Thus it may make sense to grab any chance to mate.

Little is known about the deep-sea squid lifestyle, Hoving said, so it would be useful to do DNA testing on sperm packets to find out how many males are mating with females and males. Beyond that, he said, much about the species is a mystery. He and his colleagues are currently trying to find out how long O. deletron lives.

You can follow LiveScience senior writer Stephanie Pappas on Twitter @sipappas. Follow LiveScience for the latest in science news and discoveries on Twitter @livescience and on Facebook.

© 2012 LiveScience.com. All rights reserved.

Explainer: 10 peeks at sex in the wild

  • Image: scroll fragment
    Jerome Maison  /  AP file / Warner Independent Pictures

    Emperor penguins endure some the harshest conditions on the planet — the Antarctic winter — to satisfy their primal urge for sex. The annual ritual begins with a days-long, up to 75-mile slog to their inshore breeding grounds. Once there, an elaborate courtship of calls and poses reunites old mates and enables young lovers to form lasting bonds.

    Copulation itself occurs under the cover of the dark of the polar night. Then the true sign of their devotion begins: Males huddle together to incubate the eggs as the females waddle back out to sea to feast, fattening up to provide for their newly hatched young. Once she returns, males depart in the first of a tradeoff that may, eventually, allow for healthy offspring.

    Click on the "Next" label for nine more peeps at sex in the wild.

    - John Roach, msnbc.com contributor

  • Captive pandas require help to get it on

    Image: Pandas
    Wichai Taprieu  /  AP file

    In the wild, biologists say pandas get it on without too much of a hitch. But since the wild population in China's mountain forests hovers around just 1,600, there's a push to boost the panda population in zoos around the world. And that's where the problems lie. Many pandas lack interest in their arranged mates and some inexperienced males who give it the old college try fail to engage the proper body part. As an aid, some zoo keepers attempt to arouse the bears and teach them appropriate technique with specially made DVDs, a.k.a. panda porn. When that fails — and it often does — artificial insemination is considered a last resort. These tricks combined with a better understanding of what makes the panda libido tick are beginning to pay off. The captive population has boomed in recent years.

  • Male macaques groom for sex

    Image: Japanese Macaque monkeys
    Shuji Kajiyama  /  AP

    Male macaques groom females in exchange for sex, according to a study that examined the market underpinnings of monkey sex. According to the research, based on 20-months of observation in an Indonesian nature reserve, a female is three times more likely to mate with a male if he grooms her first. Supply and demand also comes into play: Males spend more time grooming when competition for female attention is greater. Scientists refer to this practice as a biological market.

  • Male antelopes play hard to get

    Image: Antelopes
    Jakob Bro-Jorgensen / Zoological Society of London

    For highly-desired male topi antelopes in Africa, the frenzied six-week-long mating season is exhausting. Any given female is receptive for about a day, thus she wants to mate as many times as possible, especially with the fittest males. This creates intense competition for high quality antelope sperm, allowing those that possess it to be picky. A study of the phenomenon found the choosy males deliberately select the least mated females and fend off aggressive females they've already mated with. The aggressive female in the center of this image is attacking the male on the left as another female eyes the scene.

  • Sumatran rhinos tussle before they tango

    Image: Newborn rhino
    Tom Uhlman  /  AP

    Mating for the typically solitary and territorial Sumatran rhinoceros is a drawn-out affair. Studies of the critically endangered species in captivity show that when a female becomes receptive to a male's approach, she'll exhibit increased urine spraying, tail raising and swinging, and vocalizations. Foreplay includes head and genital butting, which can be a bit too much when a female isn't quite ready to tango with a young and aggressive male. But when the tussle is successful, a male will mount, often riding his mate for up to an hour. The image here shows the results of a successful mating at the Cincinnati Zoo. Such captive breeding efforts are a silver lining for conservationists hoping to keep the Sumatran rhino alive — just 300 are thought to remain in the wild.

  • Burliest walrus bulls get the harem

    Image: Walrus
    Liz Labunski  /  AP

    With a cacophony of clicks, clacks, whistles, and bellows, male walruses swim around the chilly Arctic waters vying for the attention of ice-bound females. Males will also fight off other males that get too close, sending the loser packing. Once the fussing and fighting is done, female harems surround the burliest males in the water for an underwater romp. Though scientists know little about what actually happens under the cover of the waves, they do know walruses are endowed with the mammal world's largest penis bone, called a baculum, which extends up to 30 inches.

  • Dolphin mating is brief, but bountiful

    Image: drainage channel
    Noaa  /  NOAA

    For playful dolphins, mating seems just like another carefree and pleasurable way to pass away the day. Along with some typical male posturing for access to females, there's plenty of chasing, rubbing, nuzzling and stroking that constitutes as foreplay. The belly-to-belly copulation act itself lasts less than a minute, though is often repeated several times over the course of an hour.

  • Virgin female spiders risk all for a big mate

    Image: archaeological site in Masada

    For some male spiders, sex is the ultimate sacrifice: females eat them as part of the reproductive ritual. But among the East African blood-gorging jumping spider Evarcah culicivora, shown here, males possess the coital-infused cannibalistic urge. Nevertheless, female virgins opt to be deflowered by bigger males before settling in with a small guy for the long haul. Scientists suspect females gamble with their fate once in hopes of producing larger, fitter offspring, but decide not to double down after the flirtation with danger.

  • Sappy sex for beetles of all sizes

    Kensuke Okada

    As this picture shows, Japanese sap beetles come in big, medium, and small sizes. Generally, in the beetle world, mating success is only bestowed on males with the biggest bodies because they can beat out the competition with brute force. Big sap beetles successfully employ this strategy, but when they do, the medium guys take to the air with their extra long wings and survey for sites where big males are absent. But the little guys have the biggest testicles. This allows them to hang with the big guys and sneak sex behind their backs. Since the little beetles have such big testes, they produce more competitive sperm, upping their chances at siring offspring when they get a shot.

  • Cycads have 'hot' plant sex

    Irene Terry  /  Univ. of Utah

    Hot sex has ancient roots. The males in a group of plants called cycads, which have been around for at least 250 million years, get all hot and bothered as a means to compel pollen-covered insects deep in their cones to flee forth and find a female to pollinate, according to scientists. The plants begin the process by emitting a fragrance that lures little insects called thrips into their cones. After a few hours of the thrips feasting and rolling around in there, the cycads heat up as much as 25 degrees Fahrenheit, which turns their sweet smelling fragrance into a stench. The thrips flee, some landing on benign-smelling female cycads and thus completing the pollination cycle.

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