Adaptation to hypo-saline environment of mud crab, Scylla serrata: Metabolic changes

Abstract

The present study envisaged demonstration of metabolism in the mud crab Scylla serrata during hyposaline adaptation. The crabs were collected from the estuarine regions of Goa, west coast of India in 6 pre-determined seasons (1 year) and were acclimated for 15 days (from new moon day to full moon day) every season at 1 parts per thousand (experimental group) and 12 parts per thousand (control group). Significant increase (P less than 0.001) in the rates of aquatic respiration (55-80 percent), ammonia (above 90 percent) and free amino acid (30-45 percent) excretion along with significant reduction (P less than 0.001) in the rates of urea (50-75 percent) and TMAO (15-45 percent) excretion were noticed in the crabs acclimated at 1 parts per thousand (experimental group) as compared to 12 parts per thousand (control group). In addition, analysis of crab tissue revealed significant increase in the concentration of tissue free amino acids (10-40 percent; P less than 0.001) and triglycerides (8- 40 percent; P less than 0.005), whereas significant reduction was observed (P less than 0.001) in the concentration of total protein (10-35 percent), free sugars, total carbohydrates and free fatty acids (15-70 percent) in experimental group crabs as compared to control group. The above results demonstrated that 1 parts per thousand acclimation led to utilization/mobilization of greater amount of protein and carbohydrates in order to meet the energy demand and enabled the animal to overcome the osmoregulatory / metabolic challenge.