The Transverse Septum Morphology of the Farmed Adult African Catfish (Clarias gariepinus B.) from Eastern Nigeria

The morphology of the adult African catfish transverse septum was studied to establish its functional anatomy as there is dearth of information on it from available literature. The fish sourced from commercial aquaculture was immobilized and the specimen- transverse septum dissected out, and investigated using haematoxyline and eosin stain. Grossly, the septum transversum was a milkish white membranous sheath separating the pericardial cavity from the thoraco-abdominal cavity. Histologically, the septum transversum was lined by simple squamous cells. The subepithelial region was composed mainly of loose irregular collagen fibres. Reticular fibres were also observed. Muscle tissue of mainly skeletal fibres and scant smooth muscle cells were seen embedded irregularly in the loose areolar tissue. Nerve fibres and blood vessels were also contained in this loose areolar tissue that formed the matrix of the septum transversum.