Unique mating behaviours in knife livebearers of the genus Alfaro (Poeciliidae): New observations from Alfaro huberi

Poeciliid fishes show diverse courtship displays. Building on recent work in Alfaro cultratus , we document mating behaviours in its only congener, Alfaro huberi . In both species, males adopt a unique posture above females and initiate physical contact. A. cultratus males rub the tops of females' heads with their pelvic fins, whereas A. huberi males touch females' chins with the gonopodium, a modified anal fin used in copulation. We compare these behaviours and discuss how differences may relate to the distribution of female sensory organs.