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点击量:   时间:2019-03-08 07:18:00

By Jon Copley IF YOU want to sneak into a harem, the best strategy is to dress up in drag. At least, that’s the tactic favoured by male giant cuttlefish, which turn transvestite to slip past other males guarding their mates. Cuttlefish and their cousins octopuses and squid are masters of disguise, transforming their colour, shape and texture to evade predators. The animals also use these abilities in elaborate courtship displays. For instance, male giant cuttlefish (Sepia apama) flash black and white stripes over their bodies to attract the smaller, mottled females. Large numbers of the cuttlefish gather to mate on rocky reefs at Spencer Gulf in South Australia. Whilst watching the courtship behaviour of these animals, Mark Norman of James Cook University in Townsville and Julian Finn of the University of Tasmania in Hobart noticed that small males often tagged along with breeding pairs in the guise of females. The males’ arms are usually fringed with webs, but the smaller males can retract these to impersonate the females, as well as adopting the female body colour and pattern. When the larger male is tied up fending off other rivals, the sneaky male reveals his true colours in an often successful attempt to woo the female. Furthermore, if the larger male returns to find his paramour flirting with the sneak, the smaller male can rapidly don female disguise again to avert the wrath of the spurned male (Proceedings of the Royal Society B, vol 266, p 1347). It’s not just the cuttlefish that are fooled. The biologists also have a hard time telling the impostors from the real females. “We have to follow them and see when they change back,” says Norman and Finn’s colleague Tom Tregenza of the University of Leeds, who studied their videos of the cuttlefish. He says that although there are other male animals that mimic females, none can switch its disguises on and off as easily. The cuttlefish originally transformed itself as a means of camouflage and only later turned to female impersonation, according to Tregenza. “Once you’ve got those abilities, they start to come into play for something else.” But it’s unclear whether the transvestite males are undersized or simply younger than those they cuckold—later abandoning the strategy once they are large enough to compete for mates openly. “The larger males don’t need to—they can win contests with other males,” says Tregenza. There may now be an evolutionary “arms race” between the males, the researchers suggest. Larger males may be developing better ways of spotting the impostors, while the smaller males may be refining their disguise to overcome this. “Certainly there’s a potential pressure for the impersonation to get better and better,” says Tregenza. As very little is known about the mating behaviour of cuttlefish, octopus and squid in the wild,