Beeckman, T.; Caemelbeke, K. (Ed.) (1998). Populations: Natural and manipulated, symposium organized by the Royal Society of Natural Sciences Dodonaea, University of Gent, 29 October 1997. Biologisch Jaarboek (Dodonaea), 65. Koninklijk Natuurwetenschappelijk Genootschap Dodonaea: Gent. 257 pp., more
Ontogeny of the skull may appear to occur at random, however, it does not seem unlikely that evolution will have fine-tuned this process of differentiation. The question raised here is whether some functional interpretation can be given concerning the sequence of bone formation in Clarias gariepinus, a catfish species. In the present study, 26 different specimens, ranging from 4, 1 mm Standard Length (SL) to 127,0 mm SL, were used. The first bones to appear are the opercular bone, some dentigenous bones, as well as branchiostegal rays and the maxillaries. Later, the broad hypophyseal fenestra becomes closed off by the parasphenoid and the occipital region becomes ossified. Consequently, several canal- bearing bones are formed, followed by mainly all perichondral ones. The last bones to be formed are the sphenoid bones, some infraorbitals, the suprapreopercular bone, the infrapharyngobranchials and dorsal hypobranchials. This latter stage largely corresponds to a miniature skull of the adult situation. The skull roof consists of strongly interdigitating bones that enclose two foramina and which are connected to the canal- bearing bones of the skull wall. The interopercular bones absent. Suspensorium, lower jaw and hyoid bar are heavily ossified, whereas the interhyal has disappeared. When looking at the onset of the formation of a certain bone, in relation to certain behavioural or physiological changes, there appears to be some indications of a non-random cranial ossification. Some functional interpretations can be suggested for this appearing determined sequence.
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