Estuarine mud crab, Scylla serrata (Crustacea: Decapoda) is an economically important edible species. The crustacean is widely distributed in the mud flat of the intertidal zone of Sunderban delta of West Bengal (Ali et al., 2004). Different toxicants, heavy metals and pesticides have a major role in the contamination of the aquatic ecosystem (Eisler, 1988; Selvakumar et al., 1996; Shibu Vardhanan and Radhakrishnan, 2002). All the pollutants released on land eventually find their way to the rivers and oceans as the final repository. Since the estuaries are the links to the freshwater and marine systems, they contain a variety of anthropogenic chemicals referred to as xenobiotics, viz., heavy metals, pesticides, fertilizers, etc., (Vijayavel and Balasubramanian, 2005). The arsenic contamination of aquatic ecosystem is through the use of pesticides, non-ferrous smelters, coal-fired and geothermal power plant and also from the earth's crust (Wang and Hang, 1994; Gomez-Caminero et al., 2001). Natural habitat of S. serrata faces environmental threat due to exposure of such diverse toxins including metalloid toxin arsenic (Krishnaja et al., 1987; Acharya, 2002; and Saha and Ray, 2005). Hemocytes, the chief effector cells of S. serrata are considered as prime immunoeffector cells. Diverse immunological responses including phagocytosis, nonself recognition, nodule formation, surface adhesion, cellular aggregation, super oxide anion generation, etc. are carried out by the immunoreactive hemocyte subpopulations (Sindermann, 1971; Hose et al., 1990; Soderhall and Cerenius, 1992; Johansson et al., 2000; Yildiz and Atar, 2002). In this study adult S. serrata were exposed to different sublethal concentrations (1, 2 and 3 ppm) of sodium arsenite in controlled laboratory condition for analysis of alteration of total count of hemocytes in varied span of exposure (24, 48, 72 and 96 hours). Arsenic induced modulation of total count of hemocyte of S. serrata may lead to increase in susceptibility of the animal for parasitic infection and affect normal physiology of the habitat in its natural habitat. A shift in total count under sodium arsenite exposure in S. serrata is reported for the first time.
Live adult S. serrata were collected (N = 120) from selected habitat of South 24 Paraganas district of West Bengal and transported to the laboratory. The length and breadth of the carapace were 6 ± 0.5 cm and 9 ± 0.5 cm respectively. Animals were maintained in standard glass aquaria in batches and fed with fresh flesh of molluscs. The water of the static water environment was replenished and animals were acclimatized for one week (Heasman and Fielder, 1983). The temperature of water was kept constant at 28 ± 2 oC. S. serrata were exposed to 1, 2 and 3 ppm for sodium arsenite in batches along with the control for a span of 24, 48, 72 and 96 hours duration. During the treatment, the animals received uniform ration of daylight and checked for mortality and morbidity. Fresh blood was collected aseptically from heart using anticoagulant (1% EDTA), 23 gauge sterile needle and volume of collected blood never exceeded 0.5 ml (Yildiz and Atar, 2002) from post treatment S. serrata. Total Hemocyte Count (THC) was analyzed using improved Neubauer hemocytometer (Jussila et al., 1997; and Manjula et al., 1997). |
