Female Fish Wise up to Males’ Sexual Shows

March 24, 2005

A study of fish has shown how females have triumphed in their own battle of the sexes. Males of several species of Goodeinae, a group of fish that live in central Mexico, carry yellow bands on their tails to entice females. These bands initially evolved to look like a wriggling worm, but as research in the March 24, 2005 Nature shows, females have since rumbled the males’ conniving trick.

The yellow band initially evolved as a ‘sensory trap,’ explain Constantino Macías Garcia and Elvia Ramirez. By mimicking a morsel of food, males could encourage females to hang around for longer. Indeed, males with tail bands attracted speculative bites from other fish that lacked them. But females from species with prominent male bands did not attempt to bite the males’ tails, presumably because they have stopped falling for it.

That’s not to say, however, that females ignored the males completely. They still showed a sexual interest in males with the brightest tails, suggesting that they now favour a showy tail as a badge of mating quality. The tail band has therefore become an ‘honest signal,’ the researchers conclude—probably because only the best males can afford to put on such a show and put up with constant bites from more gullible fish.

Abstract © 2005 Nature

“Evidence that sensory traps can evolve into honest signals,” Constantino Macías Garcia, Elvia Ramirez, Nature, March 24, 2005

Constantino Macías Garcia, University of St. Andrews, Fife, Scotland