Some Consequences of Transformations in Siluriform Chondrocrania: a Case Study of Clarias Gariepinus (Burchell, 1822) (Siluriformes: Clariidae)

Abstract

Several catfishes, or siluriforms, have become adapted to a benthic and nocturnal life style. Eyes have become small, whereas oral barbels and the Weberian apparatus compensate for the loss in visibility. The head has become dorso-ventrally flattened, which improves benthic stability. To give an idea of the network of consequences of such adaptations, which arise early during ontogeny, four topics are discussed. (1) Siluriformes have a platybasic skull instead of a tropibasic skull, found in most teleosts. This difference seems to be the result of a reduction in eye diameter, and has some consequences on the general form of the head, the ethmoid region and the functionality of the adductor arcus palatini muscle. (2) In Siluriformes, some general trends seem to occur in the chondrocranial roof morphology, which influence the path of some nerves. (3) Some transformations of existing structures have become part of a palatine-maxillary mechanism, which enables controlled movements of the maxillary barbels. (4) The interhyal frequently disappears during ontogeny in catfishes, which seems to be of some functional significance, again as an adaptation to a benthic life style.