INTRODUCTION:
Chlorine chloride pesticidal endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a, 6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxatrin-3-oxide) is a chlorinated hydrocarbon that is one of the most toxic pesticides for aquatic life, especially fish, and therefore has been registered as a priority pollutant by the US Environmental Protection Agency. In particular, in developing countries, endosulfan is commonly used to control pests in jute, cotton, sugar cane and vegetables. It is reported that endosulfan has been reported in connection with agricultural activities in surface waters and soil in developing and developed countries. This is more toxic to the fish model of the present study, as the fish is mud and remains in contact with the soil for a longer time. Endosulfan is moderately persistent in the soil environment with a reported average half-life of 50 days. The acute toxicity of endosulfan to fish has been previously reported.
Previous histopathological studies of fish exposed to pollutants have shown that fish organs are effective indicators of water quality. The gills are important organs in fish for breathing, osmoregulation, acid base balance and excretion of nitrogenous waste. Fish gills are also vulnerable to pollutants in the water due to their large surface area and external location. For this reason, fishing gills are considered the most appropriate indicators of the level of water pollution. Many researchers have reported histopathological changes in the gills of various fish species exposed to various pesticides. However, there was little information about the histopathological effects of endosulfan on fish gills. It was previously determined to determine the histopathological effects of the gills of a catfish, Clarias Butrachus Linn. subjected to chronic endosulfan in the present study.
MATERIALS AND METHODS:
Adult fish with an average body weight of 0.2 ± 0.03 kg and a total length of 20 ± 0.4 cm were collected from the local market. The fish was transferred to oxygen-containing containers in the laboratory. They acclimatized in glass aquariums at a constant temperature (24 ± 1 ° C) and pH 7.5 ± 0.3 7 days before the experiment. Old tap water was used for acclimatization, as well as for the preparation of test solutions. Water was continuously carbonated. Fish fed twice a day Tubifex tubifex. Endosulfan technical class (Thiodan®, 33.70% endosulfan) was provided by Hoechst Co. India Ltd.
The fish were divided into two groups and placed in separate glass aquariums. Ten fish were used for each group. Group I was subjected to commercial preparations of endosulfan. Test nominal concentrations were 0.5 µg / L for endosulfan, accounting for 1/12 of the 96-hour LC50 value. Group II was maintained in water without pesticides for control. Half the amount of water tested was updated every 24 hours. The mean values of the water quality data were 24 ± 1 ° C, pH 7.5 ± 0.3, dissolved oxygen 7.2 mg / l and total hardness 168 mg / l as CaCO3.
Clarias Butrachus exposed to endosulfan, does not detect any changes in behavioral patterns and activity of nutrition. Similarly, growth did not slow down after exposure to endosulfan, and besides mucus secretion, macroscopically open signs of pathology could not be diagnosed during the autopsy.
Both experimental and control fish were sacrificed every 15 days for 30 days. Immediately after decapitation, the gills were removed and discarded into an aqueous Buin liquid. After fixation for 24 hours, the tissues were dehydrated through a graduated series of ethanol, purified in xylene, and infiltrated with paraffin. The plot with a thickness of 4-6 microns was cut into a microtome and stained with hematoxylin-eosin. Pathological lesions were examined under an optical microscope.
RESULTS AND DISCUSSION:
Endosulfan is a chlorinated hydrocarbon insecticide and acaricide of the cyclodiene subgroup, which acts as a poison for a wide range of insects and mites on contact. Although it can also be used as a wood preservative, it is used mainly in a wide variety of food crops, including tea, coffee, fruits and vegetables, as well as rice, cereals, maize, sorghum, or other grains (Extoxnet, 1996). It enters the air, water and soil during its production and use. It is often sprayed on crops, and the spray can travel long distances before it lands on crops, soil, or water. Endosulfan on crops usually breaks in a few weeks, but sticks to soil particles and can take years to completely collapse. By hydrolysis, the expected half-lives for the alpha and beta endosulfan isomers were found to be 3.6 and 1.7 days, respectively. Endosulfan is readily soluble in water. In surface waters, it attaches to soil particles floating in water or attached to the soil below. It can accumulate in the bodies of animals living in water polluted with endosulfan (ATSDR, 2000). Endosulfan is moderately persistent in the soil environment with a reported average half-life of 50 days.
The EPA recommends that the amount of endosulfan in rivers, lakes and streams should not exceed 74 parts per billion (74 ppb). The Food and Drug Administration (FDA) allows no more than 24 parts per million (24 ppm) of endosulfan on dried tea. EPA can produce no more than 0.1-2 ppm of endosulfan on other agricultural raw materials. Commercial formulations of endosulfan are 1.88 times more toxic than its technical materials.
Histopathological changes were evident in specimens exposed to endosulfan and were not observed in control fish. After exposure, an excessive amount of mucus is observed over the gills of live specimens. It has been reported that stress caused by changes in the environment and pathological agents induces mucosal cell proliferation and increases secretion.
In the present study, after 15 days of exposure to 0.5 μg / l of endosulfan, epithelial necrosis, hypertrophy of epithelial cells, loosening of the gill epithelium, hemorrhage in primary lamellae, peeling of the respiratory epithelium and hypertrophy of epithelial cells were noted. Elevation of the epithelium, edema, epithelial necrosis, fusion of auxiliary secondary lamellae and hemorrhage in the primary lamellae were observed in the gills of the fish, examined after 30 days of exposure to 0.5 μg / l.
Epithelial necrosis and loosening of the gill epithelium are the direct harmful effects of irritants. Protective reactions of fish - excessive secretion of mucus. Lift of the epithelium, lamellar fusion and tuberiform plates can be protective, since it reduces the amount of vulnerable surface of the gill surface. Histopathological changes in gill cells can lead to hypoxia, problems with respiratory failure with ionic and acid-base balance.
RECOMMENDATIONS:
Agency for Toxic Substances and Disease Registry [ATSDR], (2000). Toxicological profile for endosulfan. Refresh , Atlanta, GA: US Department of Health and Human Services, Public Health Service.
Expansion Toxicology Network [EXTOXNET] (1996). Pesticide information profiles, files stored and archived at Oregon State University.
