SOME PHYSIOLOGICAL AND HISTOPA THOLOGICAL RESPONSES OF THE FRESHWATER FISH CLARIAS LAZERA TO ACID STRESS

Abstract

The problem of acidification of the natural water and its subsequent effects on survival of resident fish population and their extinction have received intensive studies for over a decade. In the present study, a review of pertinent literature is provided. The frame-work of the preceding study was designed to address some haematological and physiological effects of both acute (pH 3.1, TL, pH level) for 96-hours, and chronic (pHs 5.4 and 4.7) for 12-weeks, acid (H,SO,) exposure systems on the freshwater fish Clarias lazera in comparison with a control group at pH 7.1. In addition, histopathological response of the gill tissue was also assessed under chronic acid exposure systems. Behavioural responses to increased Ht ion concentration were briefly reviewed. Clarias lazera exhibited significant increases in haematocrit and haemoglobin levels during both durations. Several attempts were offered to explain the mechanisms involved in these elevations. Haemopoietic or erythrocyte mobilization response to hypoxernia, decreasing plasma volume, swelling of erythrocytes due to osmotic shifts, utilization of endocrines to more O, and/or adrenergic disturbance of the Na/H exchange.