Effect of molting on the osmoregulation of the prawn (Penaeus monodon). In：L.M. Chou et al. (ed.)

Abstract

The effects of molting on the osmoregulation of juvenile Penaeus monodon were investigated over a salinity range of 3-45 ppt. Prawn tended to conform to the environmental osmolarity during molting. Osmolarities dropped during premolt in prawn that molted in low salinities (3 and 5 ppt) while osmolarities rose in prawns that molted in high salinities (25, 30, and 45 ppt). The osmolarities started to rise or drop about 4 days before ecdysis, reached to their lowest or highest states at ecdysis, and then reverted to normal values about 3 days after molting. The rates of changes were more dramatic at ecdysis when the prawn took in large amounts of water, especially those that molted in two extreme salinities where the osmotic gradients between hemolymph and environmental medium were highest. The changes in osmolarities during the molt cycle indicate that the osmoregulatory capability of P. monodon weakened during molting, implying that the salinity tolerance of this species decreases during molting.