Comparative histomorphological assessment of the testes of two Clarias species from the Okavango Delta Panhandle, Botswana

The testes of two Clarias species from the Okavango Delta Panhandle were histomorphologically assessed for differences in structure mainly because the testes varied externally in colour, with Clarias ngamensis having black testes while those of Clarias gariepinus were off-white. Although a detailed histological description of normal testes in C. gariepinus has been compiled based on laboratory experimentation, there is limited histomorphological field data available on both species which could be used as reference material in the histology and histomorphology assessment of gonads both in the laboratory and field experiments. In August 2006 and 2007 fifteen fish per species of C. ngamensis and C. gariepinus were collected from the Shakawe Panhandle in the Okavango Delta. Testicular samples excised from the fish were fixed in 10% neutral buffered formalin and later transported to the University of Johannesburg where laboratory analyses using standard histological procedures were conducted. Microscopic assessments were used to describe the testicular morphology and the reproductive developmental stages. Haematoxylin and Eosin (H&E), Periodic Acid Schiff (PAS), Perl's Prussian Blue and Gordon and Sweets Silver Stain Solution were used to enhance finer cellular detail and the morphology of various structures present in the catfish testes. Results emanating from this study (a) form a histomorphological baseline set of data from an undisturbed wetland system for comparison between normal morphology and anomalies within the catfish species, (b) contribute to the limited database of the normal histomorphology of gonads in Southern African freshwater fish species and (c) expand the academic knowledge and skills required for the conservation of wetland ecosystems in Southern Africa.