The way to a woman's heart is through her stomach—at least for the swordtail characin. When a male of this tropical freshwater species (Corynopoma riisei) wants to mate, he dangles an "ornament"—a flag-like appendage normally hidden close to his body—in front of his desired date. The ornaments come in different shapes and sizes, and researchers have suspected since the 1960s that the shapes reflect the females' preferred foods. Now a team of researchers has confirmed this by studying female diet and male ornament variation in different populations of the fish. Ant-like ornaments (pictured) were a hit among the females who most heavily fed on ants that fell into the streams and rivers where the fish live; oval, egg-like ornaments were popular with females that preferred beetles and beetle larvae. The scientists were even able to reproduce the food-based attraction in the lab by introducing ants into the diets of aquarium-raised females who were fed flake food all their lives. After 10 days on the ant diet, these females preferred the ant-like ornaments to the beetle-like ones. The discovery, published online today in Current Biology, represents the first known example of males of any species evolving to look like dinner to better their chances with the opposite sex.
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