The cranial lateral-line system in Clarias gariepinus (Burchell, 1822) (Siluroidei:Clariidae): morphology and development of canal related bones.

Abstract

The cranial lateral-line system, as well as the canal bones are well developed in the African clariid catfish Clarias gariepinus. A generalised cranial lateral-line pattern is present (supraorbital, infraorbital, preoperculo-mandibular, otic, postotic and temporal canals). The supratemporal commissure, however, is missing, although a supraorbital commissure is present (formed through the fusion of the epiphysial branches). In addition to canals, some pit-lines are present which cover both canal regions and non-canal regions (vertical, horizontal, oral, anterior, middle and posterior pit-lines). In this paper, several ontogenetic stages of the canal related bones in C. gariepinus were studied. A description of the canal bones, as well as some considerations concerning their nomenclature are given. All canal bones develop, whereas the parietal bone seems to have fused with the supraoccipital bone during ontogeny, as has been observed in some siluroids. The extrascapulars (= supratemporals) are missing in C. gariepinus, as is the case in many siluroids. The posttemporal and supracleithral bones have fused as well. Surprisingly, some separate splenial bones, enclosing the distal part of the mandibular canal are present. Some secondary modifications indicate the apomorphic features of the Clariidae. The infraorbital bones, from which the antorbital bone has lost the antorbital commissure, and the suprapreopercular bone are enlarged, plate-like bones. The nasal bone has undergone some secondary, plate-like extensions as well.