Morfologia funcional dos mecanismos de alimentação em raias Myliobatoidei, com ênfase em espécies de Potamotrygonidae do médio rio Negro

Abstract

Studies on the feeding mechanisms in elasmobranchs have contributed to understand the mechanics of prey capture and processing; however, this kind of information is still scarce for batoids, considered important predators of the benthic fauna. This study describes the diet and feeding habits of potamotrygonid rays (Potamotrygon motoro, P. orbignyi, Potamotrygon sp. “cururu” and Paratrygon aiereba), analyze their mechanisms of prey capture, and compare these mechanisms phylogenetically related marine rays species (Dasyatis akajei, D. matsubarai and Urolophus aurantiacus). Therefore, specimens of freshwater rays from middle Negro River, Barcelos, Amazonas and marine rays from central eastern coast of Japan were studied. Lateral line canals and orobranchial musculature of these species were studied and described in order to correlate their morphology with the feeding habits of each species. The feeding behavior of P. motoro and D. akajei was studied under aquarium conditions to describe the mechanics of prey capture. Potamotrygon motoro presented carcinophagous habits, whereas P. orbignyi seems to be insetivorous and Paratrygon aiereba consumed mainly fish; Potamotrygon sp. “cururu” showed a generalized carnivorous diet. Differences on the diet may be related to the use of different types of sensitive and feeding mechanisms. In general, the lateral line system in Potamotrygonidae was similar to that of marine species. Dorsal canals possibly play an important role in identifying predators or prey positioned above the ray’s body, and ventral canals probably are employed to precisely locate the position of the prey under the disc. The study of orobranchial musculature showed a direct correlation between the relative size of different muscles and the main prey types consumed. The relative size of such muscles was also valuable to understand the mechanics of prey apprehension, manipulation and transport by P. motoro and D. akajei. Pelvic fins movements are essential to direct the mouth of the ray towards the prey during foraging by P. motoro. Overall, the information on the diet, feeding habits, lateral line system, orobranchial musculature, and feeding behavior obtained during this study allowed a broad and better understanding of the predation modes of these rays, as well as their role in aquatic communities.