EARLY DEVELOPMENT OF CEPHALIC BONY ELEMENTS IN CHRYSICHTHYS AURA TUS (GEOFFROY SAINT -HILAIRE, 1808) (PISCES, SILURIFORMES, CLAROTEIDAE)

Abstract

The inception and development of the bony cephalic skeleton of Chrysichthys auratus is described from hatching to 28 days. The larval development is divided, into morphological levels rather than following days after hatching or fry Iength. Fry were cleared by trypsin and stained with alizarine. The bony cephalic development passes through periods of fast and slow growth. These rates are not the same in different parts of the skull. The operculum, dentary and two branchiostegal rays are present after two days. The first bone appearing in the braincase is the parasphenoid; many of other bones develop subsequently and at the same time : the interoperculum, maxilla, lacrimal and upper pharyngeal jaw. The splanchnocranium continues to develop at a relatively fast rate while the neurocranium grows slowly. The braincase begins to close when the bucco-pharyngeal apparatus is aiJnost complete