VAN WASSENBERGH, S*; HERREL, A; ADRIAENS, D; AERTS, P; University of Antwerp; University of Antwerp; Ghent University; University of Antwerp: Terrestrial feeding in the eel catfish, Channallabes apus

The air-breathing catfish Channallabes apus lives in the muddy swamps of tropical Africa. Stomach contents revealed that this species selectively feeds on (mostly terrestrial) Coleoptera. Although it was originally assumed that terrestrial insects are only taken when they had accidentally fallen into the water, recent aquarium observations have shown that these fish are actually capable of capturing prey on land. During aquatic feeding, this species uses considerable suction to draw prey towards the mouth. Once out of the water, however, a flow of air is unlikely to cause displacement of the prey. Consequently, the eel catfish is forced to apply an alterative prey capture strategy. To investigate what morphological and/or behavioural characteristics enable the eel catfish to feed terrestrially, high-speed video recordings were made of this animal�s remarkable feeding mode and compared to sequences of aquatic bottom feeding. During terrestrial feeding, the catfish lifts up the rostral part of the body and points the head downwards. The anguilliform body of Channallabes apus makes it possible to assume this posture without losing stability. Next, the jaws are placed onto the prey, followed by a substantial abduction of the hyoid and the pectoral girdle. After this, the mouth closes and the catfish returns to the water holding the prey between the jaws. So, despite the drastic mechanical differences of water versus air, kinematics of suction feeding are still applied terrestrially. Yet, given the catfish�s characteristic posture when searching for food on land, these cranial kinematics do not prevent the animal to perform successful prey captures in this unusual environment.