TUBE-SNOUTED GYMNOTIFORM AND MORMYRIFORM FISHES - CONVERGENCE OF A SPECIALIZED FORAGING MODE IN TELEOSTS

GAfrican mormyriform and South American gynmotiform fishes are unique among freshwater fishes in their abilities to generate and perceive an electrical field that aids in orientation, prey detection, and commun ication. Here we present evidence from comparative ecology and morphol ogy that tube-snouted electric fishes of the genera Sternarchorhynchus (Apteronotidae) and Campylomormyrus (Mormyridae) may be unique among fishes in their mode of foraging by grasp-suction. The grasp-suction m ode of feeding is a specialization for extracting immature stages of a quatic insects that burrow into, or hide within, interstitial spaces a nd holes in matrices of compacted clay particles that form the channel bottom of many tropical lowland rivers. Ecomorphological implications of the remarkable evolutionary convergence for this specialized mode of foraging by tube-snouted electric fishes provide a challenge to Lie m's (1984, 1990) theory of separate aquatic and terrestrial vertebrate feeding modes.