Innate and Learned Shoaling Preferences Based on Body Coloration in Juvenile Mollies,Poecilia latipinna

Shoaling offers fish enhanced protection from predators through a phenomenon known as the confusion effect. This phenomenon depends on a high degree of phenotypic homogeneity within a shoal, which may confuse predators that have difficulty in targeting a single individual as prey. Accordingly, fish typically choose shoalmates with similar phenotypic characteristics to themselves. In the molly (Poecilia latipinna), dramatic differences in body coloration have been shown to affect shoalmate choice in adults. Here, we show that juvenile mollies (50 d old) were capable of shoaling and that early experience impacted shoalmate choice. When raised in isolation, mollies chose shoalmates with similar body coloration to their own. When raised with other juvenile mollies, test fish chose to associate with individuals of the same coloration as the fish with whom they had been reared. These results show that P. latipinna are capable of the behavioral plasticity that has been demonstrated in other fish species, and that early experience affects the impact of body coloration on shoaling decisions in this species.