A tropical fish uses the same tactics as human anglers to hook a mate, scientists have discovered.
The male swordtail characin has a sex ornament "lure" custom-made to appeal to hungry females.
Just as a fly fisherman uses a lure that mimics his quarry's favourite food, so the male characin adapts to carry the right bait.
The fish feed on ants, beetles, springtails and fly larvae which fall onto the water surface.
Scientists found characins that mainly eat ants also carry sex ornaments resembling ants.
Male swordtail characins, which "fish" for mates using flag-like baits on the end of a line
"This is a natural example of a fishing lure designed to maximise the chance to catch a fish," said study leader Dr Niclas Kolm of Uppsala University in Sweden. "In this case, it is not just any fish, however - it is a fish of the opposite sex that the lure is designed to catch."
Characins living in Trinidad show considerable variation in the shape of their mate-attracting ornaments.
The Swedish team suspected that the differences might have something to do with what the fish eat.
Laboratory studies showed that females fed on ants preferred to bite at the ornaments of males from ant-eating populations.
The findings, reported in the journal Current Biology, lend support to the theory that sensory stimuli can encourage animals to diversify and eventually become separate species.
They also blur the differences between food and mate preferences.
From the point of view of the female swordtail characin, the best mate is also the one that looks most like dinner.