HISTOLOGY AND HISTOCHEMISTRY OF THE LIVER OF AGE- RELATED AFRICAN CATFISH (CLARIAS GARIEPINUS) EXPOSED TO SUB-LETHAL CONCENTRATIONS OF UREA FERTILIZER.

Despite the valuable use of Urea fertilizer in agriculture, studies have it that whether acute or sub-acute concentration in water body may cause histophysiological changes in multiple vertebrate taxa. This study investigates changes in the histology and histochemistry of the liver of age-related African catfish (Clarias gariepinus) exposed to sub-lethal concentrations of Urea fertilizer. The study was carried out in the Postgraduate Research Laboratory, Department of Zoology, University of Jos, Nigeria. One hundred each of apparently healthy C. gariepinus fingerlings, juveniles and adults of mixed sex were purchased from a reputable fish farm in Jos, Plateau State and transported in an aerated plastic Jeri cans and acclimated for two weeks. During the acclimation period, fish were fed with commercial pelleted feed as reference diet. Three different types of Urea fertilizer: Indorama- N46%; Dangote – N46% and Notore – N46%were procured from Plateau Agricultural Development Program (PADP) while two types of foreign fish feeds: Copen and Skretting were procured from reliable marketers. Solubility and stability test for Urea fertilizers and fish feeds were determined. The selected Urea fertilizer was weighed into different sub lethal concentrations 0.75g/L, 1.50g/L and 3.00g/L. One kilogram each of the test feed (skretting) according to age of fish was poured into the different concentrations of Urea fertilizer to enable the feed absorb the Urea fertilizer solution for 30 minutes then sieved out and allowed to dry under laboratory condition. Each of the dried feed was labelled: 0.75g/L, 1.5g/l and 3.00g/l accordingly. The experiments were conducted in twenty-four (24) plastic bathes according to C. gariepinus age groups. A total of three test concentrations: 0.75g/L, 1.5g/l and 3.00g/l of fish feed each for C. gariepinus fingerlings, Juveniles and adults and control each duplicate replicate were labelled A1, A2, B1, B2, C1, C2, F1, F2 each for the three age groups. The 24 containers were grouped into eight according to age of fish labelled and randomly distributed on a platform in the laboratory. Ten (10) apparently healthy each of acclimated C. gariepinus age groups were exposed to each of the 24 plastic containers accordingly and each filled with dechlorinated water. The test fish were fed for 62 days within which behavioral changes were observed. Water quality parameters were determined bi-weekly throughout the exposure period using the methods of APHA. (2005). The liver organs of the C, gariepinus age groups were excised and processed routinely for variations in histology (H &E) technique and histochemistry using periodic acid Schiff (PAS). Findings revealed that significant differences (p<0.05) were recorded in the histophysiological changes of liver of C. gariepinus age groups exposed to sub-lethal concentrations of Urea fertilizer and control. In conclusion, sub-lethal concentrations of Urea fertilizer (0.75, 1.50 and 3.00g/L) has effect on the histology and histochemistry of the Liver of C. gariepinus age groups compared to the control.