Suspensão das descargas de eletrolocação-comunicação e tamanho corporal no peixeelétrico Gymnotus carapo Miller, 1966 (Osteichtyes, Gymnotidae)

Gouvêa Junior, FranciscoMary Stopa, RosaMedeiros G. de Paula, HugoHoshino, Katsumasa

Body size in many animal species determines dominance and submissive relationships, being the smallest the submissive ones. Temporary arrest of electrolocation-communication discharges characterizes submission in the low-voltage electric fish Gymnotus carapo Miller, 1966. The present study investigated if larger sized individuals of this species may also present electric discharges arrest (EDA) when stimulated by the electrical pulses generated by smaller conspecifics. The electric discharges of 20 animals (210 to 350 mm, standardlength) were monitored by polygraphic recordings, before, during and after the presentation of discharges emitted by 50-100 mm smaller fishes, maintained in an isolated aquarium. Twelve animalsshowed long-lasting EDA. The number of greater animals showing EDA raised when differences between body sizes were increased. As the same animals did not present such response when confronted with discharges emitted by animals with equivalent or greater sizes, it was concluded that the species could use the EDA, originally a defense reaction, as part of the ambush strategy for cannibalistic predation.