Effects of salinity, eye ablation and L-carnitine feed supplementation on osmoregulation of sub adult Penaeus monodon were studied with 4 levels of salinity (5,17,30 and 42 ppt). Effects of salinity on sodium, potassium and magnesium concentration in haemolymph were at different salinities while concentration were not different in all salinities. The isoionic crossover medium was 19.84 ppt for sodium ion, 23.45 ppt for potassium ion and 22.18 ppt for calcium ion. Sodium, potassium ions in the haemolymph were hyperionic regulation to medium at below isoionic concentration and hypoionic regulation at obove. Magenesium ion was hypoionic regulation to those of the medium at all salinities. Eye ablation seemed to have no effect compare to the intact prawn on osmoregulation. When they were transferred from ppt to 5 ppt or 30 ppt to 42 ppt. L-carnitine supplementation seem to have higher survival rate than control group when rearing in 30 ppt but more experiment must be confirmed. This study showed that sub adult Penaeus monodon can regulated them self to environmental effect in the type of osmoregulation.
