Osteology and morphology of the characiform fish Alestes stuhlmanniiPfeffer, 1896(Alestidae) from the Rufiji River basin, East Africa

Abstract

The osteology of a population of the characiform fish Alestes stuhlmannii, from the Rufiji River basin of Tanzania, is described, and meristic and morphometric data from over 100 specimens, ranging from 15·5 to 218 mm standard length are given. Two allometric changes occur during growth of this fish: both the number of gill rakers and the interorbital width relative to the head length increase with size. There are also changes in tooth form associated with growth in A. stuhlmannii, with the unicuspid teeth of juveniles becoming almost molariform in adults. This change in dentition with age, and therefore size, may have implications for recognizing taxa, some of which (the fossil genera Sindacharax and Bunocharax, and the living dwarf petersiines) have been distinguished by jaw or dental characters.