BASAL EXPANSION OF ANAL-FIN RAYS - A NEW OSTEOLOGICAL CHARACTER IN WEAKLY DISCHARGING ELECTRIC FISH (MORMYRIDAE)

Bone expansion of anal-fin rays in mormyrid fish is introduced as a ne w osteological character to distinguish two mormyrid species, Brienomy rus brachyistius from Nigeria and Brienomyrus kingsleyae from Gabon. T his character is sexually dimorphic and species-specific, affecting th e bases of anal-fin rays in adult males only. Between the two species, it differed in degree, the number of rays involved, and the number of the first ray affected. These differences together with differences i n conventional meristic and morphometric characters further support on going revisions of Brienomyrus taxonomy. (C) 1996 The Fisheries Societ y of the British Isles