Fish Tough Guys May Get the Girls


Female cichlid fish seem to want heroes not zeros, according to researchers at Stanford University. The female fish prefer pugnacious piscine pugilists.

The African cichlid females’ brains showed signs of anxiety after witnessing a preferred mate lose a fight with another fish. At the same time, seeing their chosen male beat down his opponent resulted in increased activity in parts of the female’s brain associated with reproduction and pleasure.

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Humans might show some of those same responses, because the brain areas involved in the cichlid’s response are similar and perform comparable functions in humans, fish, and in fact all other vertebrates, said Russ Fernald, a professor of biology at Stanford in a press release.

“It is the same as if a woman were dating a boxer and saw her potential mate get the crap beat out of him really badly,” Julie Desjardins, a postdoctoral biology researcher and lead author of the paper published in Proceedings of the National Academy of Sciences. “She may not consciously say to herself, ‘Oh, I’m not attracted to this guy anymore because he’s a loser.’ But her feelings might change anyhow.”

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In humans the subconscious change could result from failure in any competitive situation, such as losing a game or failing to get a promotion, not just physical violence, said Desjardins. Also, human males might feel a similar loss of interest if a female failed in a competition.

To observe the female fish’s reaction to male fights, the researchers split an aquarium into three see-through compartments. The female was placed in the center and the males on either side. The female would eventually select a particular male and show mating behaviors towards him.

After making her selection, the female always went back to the same male. After two days of 20-minute observations, the researchers put the males in the same compartment and left them battle it out. Following the 20-minute battle royale, the scientists dissected the females’ brains.

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“I was extremely surprised by how large a difference in brain activity we were able to measure,” Desjardins said. “To an outside observer like me, it always looked like the same thing: two similar fish fighting. But to the females, it meant something very different.”

Unfortunately, since the observation of brain activity involved killing the females, there was no way to determine if she would act upon the anxiety produced by seeing her chosen mate get whupped. The next step in the research will be to see if the female dumps the zero and mates with the hero.

PHOTO: Cichlid fish; iStockphoto

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