Habitat Ecology of a Freshwater Crab, Sartoriana spinigera (Wood-Mason, 1871) in Three Districts of Eastern Odisha

Abstract

The habitat ecology of freshwater crab Sartoriana spinigera was studied for a period of two years (January 2010-December 2011) in two distinct ecosystems viz., the canal and the ponds in three districts of eastern Odisha (Cuttack, Kendrapara and Bhadrak). These crabs were available in good numbers in the monsoon season in these districts with two peaks of abundance in each year. During the first and second year of study the total crab availability showed a greater peak in the month of August and lower in the month of April. It was found that the freshwater crab S. spinigera required an optimal habitat having a sandy clay soil. The water parameters in the study sites were found varied such as temperature 24.36 to 35.19°C, pH 5.9 to 7.6, conductivity 0.423 to 0.461µS/cm, dissolved oxygen 3.4 to 6.9 mg/l, free CO2 13.3 to 18.2 mg/l, total alkalinity 115 to 156 mg/l, phosphate 0.012 to 0.036 mg/l, ammonia nitrogen 0.008 to 0.053 mg/l and nitrate nitrogen 0.041 to 0.054 mg/l. Similarly, the sample crabs required different soil parameters in their habitats: pH 6.5-7.3, organic carbon 0.45-0.63 mg/l, nitrogen 8.28-8.84 mg/l, phosphate 1.23-1.86 mg/l and conductivity 0.053-0.072 µS/cm. Further, it was observed that to support the scavenging and omnivorous food habits of such crabs, a rich growth of micro flora and fauna was essential in their habitat. The gut content analysis of such crabs showed the presence of phytoplankton, zooplanktons like copepods, ostracods, amphipods, isopods along with crustacean larvae and their appendages, molluscan larvae, eggs of fishes, certain unidentified species and soil. This study confirmed the food habit of crabs and thus explained the role of these crabs in the food web of their habitats.