Diet composition in relation to morphology in some African, anguilliform clariid catfishes

Genera of the catfish family Clariidae that have an extreme anguilliform body shape (e.g. Dolichallabes, Gymnallabes and Channallabes) are also characterized by an extreme hypertrophy of the jaw closing muscles. Whereas it has been demonstrated that the hypertrophy of these muscles results in increased bite performance, the adaptive significance of these enlarged jaw muscles remains unclear. Given that hypertrophied forms bite harder it was suggested that the hypertrophy of the jaw adductors might be correlated with changes in diet or an altered feeding pattern. To test this hypothesis, stomach contents were analysed from specimens of a few more anguilliform species, as well as in a limited set of specimens from some of the less anguilliform clariid species. The results show that specimens with a more anguilliform body-shape have a different feeding pattern with a special preference for coleopterans. However, the absence of bite-marks on the prey retrieved from the stomachs indicated that jaw morphology and bite performance are not likely to be related to the dietary composition in the species with hypertrophied jaw adductors.