Toxicity and Histological Effects of Two Liquid Soaps on African Mud Catfish (Clarias gariepinus, Buchell, 1822) Fingerlings

Abstract

Aim: To determine the toxicity and histological effects in Clarias gariepinus fingerlings exposed to different concentrations of liquid soaps. Study Design/Methodology: A total of 500 C. gariepinus fingerlings with a mean weight of 1.7 ± 0.2 g were purchased from the University of Calabar fish farm. Samples were carefully collected and transferred to a transparent rectangular plastic container of 60 × 30 cm3 and transported to the postgraduate research laboratory, Department of Zoology and Environmental Biology, University of Calabar, Calabar, Nigeria. Fish specimen were transferred into a laboratory aquarium (80 x 30 x 30 cm3), each containing 80 litres of water and allowed to acclimate under laboratory conditions of 30.02 ± 0.09°C and a pH of 8.0 for two weeks. Twenty-five (25) fingerlings were used for each aquarium exposed to four (4) different concentrations of the two soaps (GBC car wash and morning fresh) and the control group. The fingerlings were exposed to 0.00, 400, 450, 500 and 550 ppm of the two soaps and the experiment was done in duplicate. The mean weight of fingerlings used for the study was 1.7 ± 0.2 g. The mortality data trend of fingerlings exposed to different concentrations of the soaps were dependent on the concentration and exposure duration. Results: The result of the probit transformation revealed that mortality rate increased linearly with increase in concentration of the soaps. The regression equations for the probit transformation of Clarias gariepinus fingerlings exposed to different concentration of GBC and morning fresh were y = 4.7546x – 0.6244 and y = 6.2557x – 0.6175 respectively. The 96 hours LC50 value of GBC car wash and morning fresh liquid soap on C. gariepinus fingerlings were 5.40 and 5.80 respectively. The low LC50 value for the fingerlings exposed to the soaps showed a high toxicity of the two liquid soaps. Distress behaviour was observed; they showed gasping of air, erratic swimming, piping and frequent surfacing. Conclusion: The study revealed that GBC and morning fresh liquid soaps resulted in several histological alterations in the gills ranging from erosion of secondary gill lamellae, fusion of gill lamellae and hyperplasic /erosion of gill lamellae. GBC car wash liquid soap was slightly more toxic to the test organism than morning fresh liquid soap, suggesting that the chemical constituents of GBC car wash may have more effects in other exposed non target organisms in the environment. Government should enlighten and sensitize the public on the lethal and sub-lethal effects of soap effluents to our eco-system as well as enforce against their discharges into our environment, in order to maintain a healthy aquatic environment.