Antipredator behavior in paradise fish (Macropodus opercularis) larvae: the role of genetic factors and paternal influence.

The paradise fish, a small insectivore, coinhabits marshes of Southeast Asia with several predator fish species. Its ability to recognize and avoid harmful fish may depend upon both genetic factors and experience. Here we demonstrate genetic variability between the 20-day-old larvae of two inbred strains of paradise fish (P and S) in predator exploration and avoidance, using predator models. We show that, in comparison to S larvae, P larvae exhibited an elevated frequency of leaping and backing and an increased approach latency when faced with a predator model with eyespots. Analysis of a classical cross system between the two strains revealed significant departure from an additive-dominance genetic model and suggested the involvement of both epistatic effects of several genes and paternal effects. The effect of the paternal influence during the 5-day postspawning period was found to be strain dependent: later predator avoidance behaviors were influenced by the presence of the father in P larvae but not in S larvae. On the basis of these and previous results, we speculate that the 5 postspawning days may represent a developmentally sensitive period during which specific environmental stimulation, e.g., stimuli associated with the father, is critical for later development of appropriate antipredatory responses. We conclude that developmental aspects of antipredatory behavior in paradise fish are influenced by a complex interplay between genetic and environmental factors.