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Comparative study of the taste attractiveness of different aquatic invertebrates (daphnids Daphnia longispina and D. pulex, larvae of Chironomidae, whirligig Gyrinus marinus, water skaters Gerris spp.) and plants (duckweed Lemna minor, filamentous alga Cladophora sp.) for roach Rutilus rutilus, bitterling Rhodeus sericeus amarus, and rainbow trout Oncorhynchus mykiss has been performed. Roach's taste preferences for agar-agar pellets, containing the aqueous extracts of the organisms under study, varies from maximum (daphnids, filamentous alga, larvae of chironomids) to minimum (duckweed) or it can be absent (whirligig). Different taste preferences to pellets containing the extracts of aquatic organisms has been also found in bitterling (daphnids, larvae of chironomids, water skaters) but not in rainbow trout (daphnids, water skaters). It has been suggested that whirligigs and water skaters do not contain any deterrent substances ensuring chemical defense from predators. It has been demonstrated that intraoral gustatory reception of food items follows two alternative behavioral stereotypes that are different from each other in the time during which food items are retained in the oral cavity and the number of manipulations (subsequent grasps of a food item) during the perception process. We discuss the importance of gustatory reception as the major sensory mechanism that ensures feeding selectivity of fish and decreases interspecific competition over food. [ABSTRACT FROM AUTHOR]