Convergence in the feeding mechanics of ecomorphologically similar species

We examined the hypothesis that fish species with similar ecomorphological patterns, but from different taxonomic groups, would use similar feeding modes. We contrasted the feeding behavior of Micropterusalmoides(Lacépède) (Centrarchidae) and Cichla ocellaris(Block and Schneider) (Cichlidae), both large-mouthed piscivores with a locomotor morphology designed for fast acceleration, with Lep mispp. (Centrarchidae) and Cichlosomaseverum(Heckel) (Cichlidae), both small-mouthed predators on benthic invertebrates with a locomotor morphology designed for maneuverability. Pressure profiles in the buccal and opercular cavities were more similar for species that shared ecomorphological patterns than for species that shared phylogenetic histories. For small-mouthed predators, minimum buccal pressures were significantly greater and occurred earlier than the corresponding opercular pressures. For both large-mouthed predators, minimum buccal and opercular pressures were similar in magnitude and in timing. We developed the ram–suction index (RSI) to identify the relative contributions of ram feeding (i.e. predator movement) and of suction feeding (i.e. prey movement) to shortening the predator–prey distance during the strike. The RSI values for small-mouthed predators fell closer to the suction end of the ram–suction continuum than did strikes by the large-mouthed predators. The RSI provides a bench mark for evaluating the hydrodynamic consequences of intraspecific, interspecific and interprey variation in strike mechanics