Osmoregulation in Penaeus monodon: Effects of molting and external salinity

Abstract

The effect of molting on osmotic, chloride, calcium and total protein concentrations in the hemolymph of the shrimp Penaeus monodon was investigated. Regardless of medium salinity, tissue water as well as osmotic and chloride concentrations in the hemolymph became stable within one day after molting. In general, total protein concentrations remained stable throughout the molting cycle. Large fluctuations in hemolymph calcium were observed 0-6 hours after molt. In low salinities, hemolymph calcium peaked at 3 hours postmolt to values 30% higher than those during molt. These values subsequently decreased rapidly one after molting, when hemolymph concentrations achieved intermolt values. At 44 ppt, calcium concentrations were highest during molt, then gradually declined by about 15% to intermolt values.