Evaluation of toxicity and response of African catfish (Clarias gariepinus) exposed to manganese chloride solution

Abstract

This study investigated the acute toxicity and behavioural response of African catfish (Clarias gariepinus) to manganese chloride (MnCl ) solution.  One hundred (100) pieces of juvenile Clarias gariepinus were acclimatized 2 for 14 days in ten (10) plastic bowls containing 25 L of water each. The acute-toxicity of manganese chloride, LC and sub chronic exposure (28 days) were investigated. For sub-lethal exposure; fifty pieces of C. gariepinus  50 were divided into five groups of ten in bowls labelled (A to E). The fish in groups (A to D) were exposed to manganese chloride solutions at: 68.5, 137, 205.5 and 274 mg/L respectively while group G served as the control. On day 28, the exposed fish were sacrificed; blood, muscle, liver, and gills were collected for haematological and histological studies. The activities of the superoxide dismutase (SOD) and glutathione-Stransferase (GST) were determined using standard methods. The manganese concentrations in the liver, gills and muscle tissues were determined using Atomic Absorption Spectrophotometer (AAS). The LC obtained 50 was 2.74 g/L. The mean water temperature showed that there was no significant variation at (p < 0.05) between the control and other groups. The results of growth parameters showed that fish exposed to 137 mg/L manganese  concentration had better growth performance than those exposed to higher concentrations. The activities of SOD and GST in the liver of fish  increased significantly (p < 0.05) as manganese concentration increases. The red blood cells concentrations decreases while white blood cells  increases as the concentration of manganese increases respectively. The mean bioaccumulation of manganese in the organs of C. gariepinus followed the order of liver > gill > muscle. The histopathological study revealed alterations in the liver, gill and muscle tissues. This study concluded that manganese at concentration greater than 137 mg/L elicits adverse effect on C. gariepinus growth performance, haematology, histopathology as well as liver SOD and GST activities.

Key words: Behavioural response, Cat-fish, Juvenile, Manganese chloride, Toxicity