Comparative osteology and three dimensional computed tomography of Nile catfishes, in relation to feeding mechanisms

Abstract

Introduction:For the first time three-dimensional Computed Tomography was used in a study concerning Nile catfishes heads. Methods: The present study is carried out on 40 heads of four examplar species of catfish families, Bagridae (B. bajad); Clariidae (C. garpineus); Malapteruridae (M. electricus) and Mochokidae (S. schall). Specimens are double-stained for cartilage and bone, as done by Taylor and Van Dyke (1985). Results: the skull of M. electricus was consisted of both bones and cartilage, as the frontal, parietal, supraoccipital, postparietal, sphenotic and pterootic were remained cartilages in mature fish. In order to ease the studying process the bones of catfish skulls were arranged in clear twelve series. This arrangement may facilitate the diagnosis of the malformations and other related diseases. Despite the similarity of the feeding apparatus in the Nile-catfish, they have different feeding mechanisms. B. bajad able to feed on large sized preys because of the free branchiostegeal membrane, the large dimensions of the oral and pharyngeal gap limits. M. electricus has another method as we suggest that the liable cartilages which form the skull roof are easily squeezed by voluminous muscles, raise the roof of the mouth and expand the oropharynx. In S. schall the narrow oropharyngeal limits and the subterminal mouth are suitable for sucking small mollusks, a process aided by the hard pad of the upper lip and the brush like mandibular teeth. Conclusions: This work provides an anatomical description of the fish heads using 3D CT which may facilitate the diagnosis of malformations and other related diseases. It also discussed the different feeding habits of the Nile Catfish.