ScienceShot: Distracted Female Fish Lose Weight

Flashy colors and elaborate dances help the males of many species score a mate. But sometimes these showy displays hurt females, according to a study published online today in the Proceedings of the Royal Society B. The new work concerns splitfins (Goodeidae), a family of small North American fish whose males sport a vertical yellow stripe on their tail, which they wave to mimic wriggling prey. The ruse attracts females—but it also causes them to lose weight. When the researchers presented pregnant (and thus hungry) females from six species of splitfins with both yummy insect larvae and males from two of the most flamboyant splitfin species—the polka-dot splitfin (Chapalichthys pardalis) and the butterfly splitfin (Ameca splendens)—the females from all six species were so distracted by the males' tails that individuals from five of the species lost weight over the 1-week trials. Females that lost the least amount of weight were from species in which males sported more conspicuous tails. The authors speculate that this was because the females had learned to separate sexual attraction and feeding behavior over time, preventing them from confusing fake food for the real thing.

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