Cranial morphology of the anguilliform clariid Channallabes apus (Gunther,1873) (Teleostei : Siluriformes): are adaptations related to powerful biting?

Within the clariids (air-breathing catfish), a complete range of fusiform t o anguilliform species can be observed. This study deals with the cranial m orphology of Channallabes apus, an extreme anguilliform (eel-like) species, compared to the anguilliform Gymnallabes typus and the more fusiform Clari as gariepinus. The overall morphology of the head of Channallabes apus show s a hypertrophied adductor mandibulae complex, with the corresponding subst antial narrowing of the neurocranium, seen in the frontals, the sphenotics, the pterotics and the post temporo-supracleithra, as well as the reduction and displacement of the eyes and some canal bones, such as the infraorbita ls and the suprapreopercles. The presence of a hypertrophied muscle complex possibly indicates that a more powerful bite may occur. This implies that adaptations can be expected in several parts of the skull. On the lower jaw of C apus a higher coronoid process is found, and on the suspensorium, two sets of three processes are present on the hyomandibular bone, indicating a stronger connection to the neurocranium. Several of the observed features , such as the elongation of the body, the reduction of the eyes, the increa se in vertebrae number, limblessness and the increasing rigidity of the sku ll, may also be related to a process of miniaturization.