Effects of prey type on suspension-feeding behavior in Nile tilapia

Quantitative analysis of feeding behavior in the Nile tilapia,Oreochromis niloticus(Linn.), assessed the frequencies and functions of five behaviors (long pumps, short pumps, benthic pumps, reversals, spits) during suspension feeding on four prey types (whole TetraMin flakes, crushed TetraMin flakes, brine shrimp, bacteria). We tested the hypothesis that suspension-feeding behavior is affected by prey type. Long pumps occurred significantly more frequently (p= 0.01) during feeding on bacteria (2-8 ×10^sup 5^ cells ml^sup -1^) than on other prey. Short pumps, with a substantially reduced gape and significantly shorter duration (p < 0.0001) relative to long pumps, appeared to separate organic particles from inorganic material such as gravel. Benthic pumps were directed at food that had settled on the substrate, which also resuspended organic particles into the aquarium water due to substrate disturbance. Reversals, shown previously to generate a posterior to anterior water flow within the oral cavity, function both to separate organic from inorganic particles by resuspension within the oral cavity and to transport prey retained in mucus. Spits expelled inorganic material through the mouth, and occurred significantly less frequently (p = 0.04) during feeding on brine shrimp versus whole or crushed flakes. Prey type affects the frequency of specific behaviors for prey collection and processing during suspension feeding, providing insight into the functions of these behaviors.[PUBLICATION ABSTRACT]