Within the family Clariidae or air breathing catfishes, several species have developed unusually large (hypertrophied) jaw closing muscles. The extremely hypertrophied morphs (C and D of the figure on the left) have jaw adductors with physiological cross-sectional areas of up to 7 times those of the non-hypertrophied morphs (for a given skull length).

Inevitably, the extreme variation in this component of the cranial musculo-skeletal system will have important consequences on its function during feeding. Biomechanical modeling has shown that species with enlarged jaw closers can theoretically produce a higher maximal biting force (Herrel et al., 2002). However, biting is only one of the many functions of the cranial musculo-skeletal system in fish. As the hypertrophied jaw muscles also strongly interact with the suspensorium and the neurocranium, effects on the structure and mechanics of the bucco-pharyngeal expansion apparatus (responsible for prey capture, -transport, -processing, aquatic respiration and air-breathing) are expected. The aim of this study is to investigate the consequences of jaw closer hypertrophy on feeding in clariid catfishes.

Clarias gariepinus (A)

Clariallabes longicauda (B)

Gymnallabes typus (C)

Channallabes apus (D)