Melatonergic regulation of hemolymph sugar levels in the freshwater edible crab, Oziotelphusa senex senex.

In this study, the hyperglycemic effect of melatonin in the freshwater edible crab, Oziotelphusa senex senex, is investigated. Injection of melatonin induced hyperglycemia in a dose-dependent manner. Administration of melatonin produced hyperglycemia in both intact and eyestalk-ablated crabs. Bilateral eyestalk ablation resulted in significant increase in the total carbohydrates and glycogen levels with a significant decrease in phosphorylase activity in the hepatopancreas and muscle of the crabs. Injection of melatonin resulted in significant decrease in the total carbohydrate and glycogen levels, with an increase in phosphorylase activity in hepatopancreas and muscle of both intact and eyestalk-ablated crabs. From the results, it is hypothesized that melatonin-induced hyperglycemia in the crab, O. senex senex, is not mediated by eyestalk hyperglycemic hormone. 2010 Wiley-Liss, Inc.