Gender-bending mollusc shows coital cunning

Agence France-Presse

Posted at Jul 05 2012 12:09 AM | Updated as of Jul 05 2012 08:09 AM

PARIS - Scientists have observed a cross-dressing cuttlefish take sexual trickery to new depths.



On one side of its body, it adopts female markings to deter potential rivals, while on the other, it displays brilliant masculine colours, enabling it to flirt furiously with partners-to-be.



This behaviour in the male mourning cuttlefish, a squid-like creature common off Australia's east coast, is meant to boost mating chances in a short-lived species where discerning females far outnumber fiercely competitive males.



"On one side of their body they have this female coloration, they mimic the female that they are courting, and on the other side they have the full sexy male display going on," behavioural ecologist Culum Brown told AFP.



The male "is very, very vibrant, pulsating black and white stripes, high contrast, it is an amazing visual display, you can see it from a long, long way away."



The female, on the other hand, is a "boring, mottled brown colour" that is good for disappearing into the background.



Brown of the Macquarie University in Sydney's biological sciences department, is one of the authors of a paper published Wednesday in the Royal Society Journal Biology Letters.



He suggested the cuttlefish, about 15 centimeters (six inches) long when fully grown, evolved the unusual technique to improve its chances of reproduction.



It can strut its best stuff in the direction of a female while staying off the radar of rival males by turning its well-camouflaged side their way.



"If you go straight up to a female and use your male display on both sides of your body, and as we said you can see that from a very long way away, that immediately tells all other male cuttlefish in the area that this particular male found a female.



"What that means is that every other male is going to come and investigate. They compete, they beat each other up and chase each other away. So clearly the best thing to do is to not attract the attention of other males," said Brown.



The cuttlefish only adopt this split personality when there is another male around.



If they are alone with the female, or there are too many other cuttlefish around, the animal switches off its mixed signals.



"If there are more than one male, or indeed more than one female, then you can't do it anymore because you can't possibly orientate yourself in a way that actually works," said Brown.