Ontogeny of the maxillary barbel muscles in Clarias gariepinus (Siluroidei: Clariidae), with some notes on the palatine-maxillary mechanism


* Address for correspondence: e-mail: Dominique.Adriaens@rug.ac.be


Siluroids are characterized by the presence of a palatine-maxillary mechanism, which enables a controlled mobility of the maxillary barbels. In Clarias gariepinus, the ontogeny of this mechanism is studied and described as well as those muscles related to the maxillary barbel. Two muscles are distinguished: (1) retractor tentaculi, connecting the maxilla to the suspensorium, and (2) extensor tentaculi, running from the ventro-lateral face of the skull to the posterior half of the palatine. These typical catfish muscles are derived from muscles that are present in generalized teleost fishes. The retractor muscle is believed to be derived from the A3 muscle of the adductor mandibulae complex. The extensor muscle is formed from the anterior fibres of the adductor arcus palatini. The palatine is rod-like in C. gariepinus and articulates with the orbitonasal lamina in larval specimens and with its ossification, the lateral ethmoid, in juvenile and adult specimens. The articulation occurs via a long cartilaginous strip on the dorsal face of the autopalatine, thereby enabling both a rotation and a restricted sliding.