Physiological Changes in Clarias gariepinus Induced with Bacillus Species Used as Biological Agent in Aquatic Environment

Abstract

In order to study the potential use of Bacillus subtilis and B. cereus as biological control agents of mosquitoes larvae in aqueous environments as happens with B. thuringiensis var. israelensis, fish model was used hence treatments with these bacterial species will be in aquatic environment. The aim of the study was to evaluate any possible physiological alterations and toxicity to aquatic animals (catfish by inoculation with bacillus species). In this view, dissolved oxygen (DO), chemical oxygen demand (COD), pH of the experimental water culture was estimated. Effects of the Bacillus species were also monitored in fish haematology and histopathology of gill and liver tissues. Results showed that there was no significant variation (P<0.05) in the water quality parameters with catfish inoculated with B. thuringiensis and B. subtilis in comparison with the inoculation with the B. cereus. In the haematological parameters, values obtained from catfish inoculated with B. thuringiensis and B. subtilis treatments were related to values of the control group. Changes in body weight of B. cereus treated fish were reflected in the liver tissue histopathology with severe hepatic and damages to gill rakes and filaments. Summarily, the safety of B. subtilis as a biological control agent in an aquatic environment is guaranteed but B. cereus as an alternative to the existing biological control agent lack valuable safety records as it can cause harm in aquatic animals and human environments.