Male deep-sea squid seeks mate of either sex for fun in the dark
By Ian Sample
Scientists have identified another mishap that can result from sex in the dark after filming creatures that live in the deeps of the Pacific Ocean.
Footage from remote-controlled submersibles revealed that male deep-sea squid struggle to distinguish between potential mates and members of the same sex in the dimly lit waters.
But instead of developing keener senses to help find a partner, the male of the species has adopted a sexual strategy to suit the conditions: it mates with any deep sea squid it comes across.
Researchers blame bad light, similar male and female body size and the rarity of encounters for the squid's indiscriminate behaviour, which leaves its mark on the bodies of unsuspecting males in the form of spent sperm sacs.
Henk-Jan Hoving, a marine biologist at the Monterey Bay Aquarium Research Institute in California, said that wasting sperm was apparently less costly for the males than honing their ability to spot females.
His team found evidence of the squid's "shot-in-the-dark" approach to sex when they examined screen grabs from video recorded at depths of 400-800 metres in the Monterey submarine canyon off the coast of California. To their surprise, as many males as females carried spent sperm sacs on their bodies, a sure sign that males had attempted to mate with them.
In a report published in the journal Biology Letters, the authors claim the behaviour "exemplifies the 'live fast and die young' life strategy of many cephalopods."
The study centred on a squid species called Octopoteuthis deletron. When the squid mate, the male releases a sperm-filled bag that discharges into the female's tissues. The act is swift, but leaves empty sperm sacs on the female body as an outward sign of recent mating.
Underwater footage of the squid in action was recorded by robotic submersibles between 1992 and 2011. Though 108 squid were filmed, 15 were juveniles and in 54 cases, it was impossible to determine the maturity of the squid, their sex, or whether sperm sacs were present on the animals' bodies.
Among the remaining squid were 19 females and 20 males, of which 10 females and 9 males had visible sperm sacs on their bodies. Those left on the males were in such positions that they must have been left by other males, the researchers note.
In some species, such a scattergun approach to mating might be seen as a waste of valuable sperm. But the squid are solitary creatures and encounter other members of the species only rarely, and since males and females are the same size and shape, it is hard to tell the difference in the dark. When sex is so rapid, evolution favours multiple matings with any individual encountered.
"Deep-sea squid are extremely important in the oceanic food webs as tuna and many other fish feed primarily on them. However, our knowledge of these animals is very limited," Hoving told the Guardian.
"Squid, including deep-sea species, only reproduce once and they have to find mates in time in an environment where encounters between individuals of the same species are few and far between."
© 2011 Guardian News and Media Limited or its affiliated companies.
This article originally appeared here.
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