Fickle fish change sex at will

SYDNEY – Fickle coral reef fish can change sex according to the company they keep, a new study by US and Australian scientists showed on Monday.

Young bluehead wrasse choose their sex according to the crowd they grow up with in what appears to be the ultimate example of peer pressure, according to the study. “It turns out that social effects are really important to whether a bluehead wrasse becomes a male or a female when it is young,” said Doctor Philip Munday, of the Centre of Excellence for Coral Reef Studies and the School of Marine and Tropical Biology at James Cook University in Australia’s Queensland state.”These fish are very sensitive to their social surroundings which ultimately determine whether they will become male or female,” he said of the study conducted along with the University of California, Santa Barbara.The fish have developed their flexible gender structure to increase their chances of breeding, the study that was published in the scientific journal Proceedings of the Royal Society B: Biological Sciences.The fish, which start life as larvae without a specific sex, become either male or female as they develop.But young males appear to be able to alter their sex depending on how many other fish there are living around the same reef.The scientists found that there was a much greater chance of the youngsters turning female if there were only a handful of the species in one area as they would have a much greater chance of breeding than males.If there were many fish in the social group, the youths are likely to undergo a dramatic transformation and become male, the study indicated.”This shows that sex is not genetically predetermined, as it is in mammals and birds”, said Munday, explaining that far fewer fish became male when reared alone.In addition, the study showed, some fish could even change sex as adults depending on the breeding conditions around them.”When these fish alter their sex from adult female to adult male the change is very dramatic.They look completely different, their sex organs transform, their behaviour changes – their whole life story,” Munday said.Nampa-AFP”It turns out that social effects are really important to whether a bluehead wrasse becomes a male or a female when it is young,” said Doctor Philip Munday, of the Centre of Excellence for Coral Reef Studies and the School of Marine and Tropical Biology at James Cook University in Australia’s Queensland state.”These fish are very sensitive to their social surroundings which ultimately determine whether they will become male or female,” he said of the study conducted along with the University of California, Santa Barbara.The fish have developed their flexible gender structure to increase their chances of breeding, the study that was published in the scientific journal Proceedings of the Royal Society B: Biological Sciences.The fish, which start life as larvae without a specific sex, become either male or female as they develop.But young males appear to be able to alter their sex depending on how many other fish there are living around the same reef.The scientists found that there was a much greater chance of the youngsters turning female if there were only a handful of the species in one area as they would have a much greater chance of breeding than males.If there were many fish in the social group, the youths are likely to undergo a dramatic transformation and become male, the study indicated.”This shows that sex is not genetically predetermined, as it is in mammals and birds”, said Munday, explaining that far fewer fish became male when reared alone.In addition, the study showed, some fish could even change sex as adults depending on the breeding conditions around them.”When these fish alter their sex from adult female to adult male the change is very dramatic.They look completely different, their sex organs transform, their behaviour changes – their whole life story,” Munday said.Nampa-AFP