Osmoregulation in Penaeus monodon: effects of molting and external salinity

Ferraris, R.P.; Estepa, F.D.P.; De Jesus, E.G.; Ladja, J.M. . Aquaculture Dept.

Osmoregulation in Penaeus monodon: effects of molting and external salinity

1986

Ferraris, R.P. | Estepa, F.D.P. | De Jesus, E.G. | Ladja, J.M. (Southeast Asian Fisheries Development Center, Iloilo City (Philippines). Aquaculture Dept.)

The effect of molting on osmotic, chloride, calcium and total protein concentrations in the hemolymph of the shrimp Penaeus monodon was investigated. Shrimp were stocked in various salinities and then sampled during molt and after molting. 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 day 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. At this salinity, shrimp, were also dehydrated during molt, but % tissue water increased to normal intermolt values within one day after molting. The converse situation was observed in shrimp at low salinities. Shrimp tended to conform more to the environmental osmolarity 0-6 hours after molt than shrimp 12 hours to 14 days after molt. Isosmotic points were higher during molt than during intermolt. Hemolymph chloride was very well regulated below 2 ppt medium chloride regardless of molting stage. Above 20 ppt, newly molted animals tended to conform to the external chloride concentration when compared to intermolt stages. The isoionic points were independent of molt stage.

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