Gonopodium

A gonopodium is a modified anal fin (it looks rather like a thin rod) that allows male fish of the families Anablepidae and Poeciliidae to briefly hook into the vent of a female fish to deposit sperm.

This fin is normally held back and the male fish turns it down and forward just before mating.

Typical male fish with this fin are:

• Guppys
• Mollies
• Platy
• Swordtail
• Endler's livebearer
• Anableps anableps

• See also Andropodium