September 21, 2011
The Secret Sex Life Of The Promiscuous Deep-Sea Squid
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By studying footage taken by submersible vehicles, researchers, led by Hendrik Hoving of the Monterey Bay Aquarium Research Institute (MBARI) in Moss Landing, California, found that this rarely seen marine creature will often engage in same-sex mating.
The reason for these encounters, researchers believe, is because in the dark depths where these animals live, squid may be unable to distinguish between sexes and, therefore, deposit their sperm packets on any squid they encounter.
The difference between sexes is so slight and meetings with other squid are so rare that the mating males are either unaware or unconcerned whether the receiving party is female or not, the researchers said.
Publishing the findings in the Royal Society journal Biology Letters, Hoving and colleagues said the squid only have a single, brief reproductive period during their short lifespan and will mate with any partner they encounter during this time regardless of its gender.
Chance-meetings are so rare, that some specimens can drift a lifetime without ever encountering another squid, much less the opposite gender.
Hoving and his colleagues had suspected male deletron were depositing their sperm sacs on other males, based on empty spermatangia (squid sperm sacs) found on the surface of dead males caught in fishing nets, but needed to investigate further to be sure.
The team studied video footage taken over 20 years by remotely operated vehicles (ROVs), most of which was recorded in the Monterey Submarine Canyon off the coast of California.
Little was known of this creature´s sex life until now. Researchers have known previously that the male uses a long, penis-like organ to deposit the sperms sacs onto a female, which are then absorbed into her tissue.
By studying the footage, the team found out their suspicions rang true. The video footage captured 108 individuals, of which only 39 could be identified gender-wise: 19 females and 20 males.
While none of the specimens were caught mating, the team did find that 9 male squid and 10 female squid had clusters of spermatangia attached to their bodies, front and back.
“Males were as likely to be found mated as females,” the authors said. Based on the evidence, male squid “routinely and indiscriminately mates with both males and females.”
The unusual behavior may be explained by the fact the squid is boosting its chances of successfully passing on its genes in the challenging environment in which it lives. The costs involved in wasting sperm on another male are probably smaller than the costs of developing courtship or the ability to discriminate between sexes.
“This is a solitary species that is not very abundant; it lives in deep, dark waters where opportunities for reproduction are few and far between. In response to that challenge, this reproductive strategy ensures that no opportunity for successful mating is lost. It's kind of like buying a Lotto ticket, except the odds are much better,” co-author Bruce Robison explained.
“This behavior further exemplifies the ℠live fast, die young´ life strategy of many cephalopods,” said Hoving.
Experts have previously observed more than 1,000 different animal species, including dolphins and primates, engaging in same-sex coupling.
The researchers now hope to use genetic techniques to determine the paternity of the sperm packages, to determine whether more than one male is trying to deposit its sperm onto males and females.
Image Caption: A female Octopoteuthis deletron in the water column observed by MBARI´s remotely operated vehicle Ventana on December 6th 2007. This animal was observed at 854 meters depth in Monterey Canyon. Spermatangia were present on the dorsal arms. (MBARI)
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