Meristic Characters and Electric Organ Discharge of Mormyrops curviceps Roman (Teleostei: Mormyridae) from the Moa River, Sierra Leone, West Africa

Abstract

Mormyrids of the genus Mormyrops were collected from the Moa River around Tiwai Id., Sierra Leone, West Africa. Meristic analysis and comparison with paratypes identify these fish as Mormyrops curviceps Roman. They differ from M. deliciosus (Roman) in seven meristic characters: the number of lateral-line scales, caudal-peduncle scales, total vertebrae, caudal vertebrae, anal-fin rays, and teeth on the upper and lowerjaws. From M. curviceps we recorded two electric organ discharge (EOD) pulse types, which were not related to developmental stage or sex. Individual EOD lasted on average either 0.471 msec (with a major head-positive phase followed by an equally large head-negative phase), or about three times longer (1.611 msec) with reversed polarity (i.e., a major head-negative phase), followed by a major head-positive phase. We contrast two views concerning mormyrid EOD: 1) the EOD of M. curviceps simply exists in two pulseform morphs; and 2) characteristics of the EOD pulse-form function as a reproductive isolating mechanism, suggesting the existence of sibling species.