by TFH Magazine on July 13, 2012 at 5:49 am
By Ed Yong
Anglers ensnare fish with bait, or with man-made lures that look like bait. Anglerfish do the same thing – they have worm-like growths on their heads that act as living fishing lures to entice their prey. The swordtail characin, a small fish from Trinidad and Venezuela, has a similar lure, and it uses it not to attract food, but sex.
The male characin has a small bean-shaped patch attached to his gill flaps by a thin thread. When he swims, he holds these ‘flags’ against his body. When he encounters a female, he flares one of them out in front of her. The female clearly thinks that the flag is food, for she bites at it vigorously. While she’s occupied, the male sidles across and impregnates her with his sperm.
Photograph courtesy of Discover Magazine