Effects of ultraviolet photooxidation of cypermethrin on the activities of phosphatases and digestive enzymes, and intestinal histopathology in African catfish, Clarias gariepinus (Burchell, 1822)

Abstract

The possibility of ultraviolet (UV) photooxidation of cypermethrin generating more toxic intermediates or isomers demands that studies that look at the effects of cypermethrin and UV irradiation under a coexposure scenario be carried out. In this study, juvenile African catfish (Clarias gariepinus) were exposed to 50 µg/L cypermethrin, 100 µg/L cypermethrin, UV, 50 µg/L cypermethrin + UV or 100 µg/L cypermethrin + UV, in a static renewal for 3 weeks. The control fish were maintained in uncontaminated water, and not exposed to UV radiation. After the exposure duration, the fish were killed, and the activities of acid phosphatase, alkaline phosphatase, amylase, protease, and lipase were determined in the liver or intestinal homogenates. Also, the histopathology of some sections of the intestine was performed. The results showed that the activities of the enzymes decreased significantly following exposure to cypermethrin while there was no change in the activities of the enzymes due to UV irradiation alone. The histopathological analyses indicated that exposure to cypermethrin caused alterations in the histoarchitecture of the fish such as severe erosion of the mucosa layer, faded lamina propria, and disintegration of the muscle layer. The exposure of fish to both cypermethrin and UV irradiation caused significant decrease in the activities of the enzymes. This could be an indication that UV irradiation has the tendency to potentiate cypermethrin‐induced toxicity in fish.

Tissue Distributions and Toxic Effects of Hexavalent Chromium in Laboratory-Exposed Periwinkle (Littorina littorea Linnaeus)

“…There have been disparities in the levels and patterns of tissue-specific accumulation of hexavalent chromium in laboratory-exposed aquatic organisms. For example, the gills and digestive glands levels of hexavalent chromium in the bivalve mollusk, Venus verrucosa were 180 and 150 µg/g, respectively, while a tissue concentration as low as 1.73 µg/g in the gills of a fish chronically exposed to 5.3 mg/L hexavalent chromium [21,31]. Comparatively, the levels of hexavalent chromium in the tissues of periwinkles were low ranging from 0.40 to 0.48 µg/g in the gills to 0.67-0.78 µg/g in the brain.…”

“…The changes in the histological architecture have been used as indices of the physiological effects of pollutants on organisms [30,31]. The tissue-specific histological changes in animals have been shown to relate to the extent of pollutant accumulation in the tissue [48,49].…”

“…In the present study, exposure to hexavalent chromium resulted in several changes in the histological structures of the tissues of L. littorea such as atrophy of neuronal cells, necrosis and atrophy of the gills' secondary lamellae, degeneration of mantle's secretory cells, degradation of the villi epithelial cells, and atrophy and degeneration of foot's myofibers. Although the reports of histopathological effects of hexavalent chromium in periwinkle and aquatic mollusks are scarce, a number of studies have shown that exposure to chromium resulted in histological changes in the tissues of fish and other aquatic animals [18,31,[50][51][52]. The histopathological changes are physiological responses to defend the animals against assaults by toxicants [31].…”

“…Although the reports of histopathological effects of hexavalent chromium in periwinkle and aquatic mollusks are scarce, a number of studies have shown that exposure to chromium resulted in histological changes in the tissues of fish and other aquatic animals [18,31,[50][51][52]. The histopathological changes are physiological responses to defend the animals against assaults by toxicants [31]. For example, histological changes such as hyperplasia and hypertrophy, and fusion of lamellae have been identified as defense mechanisms to minimize the toxic effects of pollutants in fish [53].…”

“…The procedures described by Adeyemi et al [31], with slight modifications, were followed for the histopathological analyses. The soft tissues (brain, gills, intestine, foot, and mantle) were fixed in 10% formaldehyde for 24 h, after which they were dehydrated in ethanol gradients.…”