Individual Penaeus chinensis adults (26.91 + 4.66 g) were subjected to 0.03, 5.10,

The effects of eyestalk ablation on the acid-base balance of the haemolymph and on the haemocyanin concentration of Penaeus monodon were investigated in a period of 24 hrs. The pH of the haemolymph was low in the shrimps treated bilaterally, intermediate in the shrimps which were unilaterally treated, and high in intact shrimps. The treatment of eyestalk ablation resulted also in a decrease of haemolymph pO2 tension. The pO2 of the haemolymph was low in the shrimps treated bilaterally, intermediate in the shrimps treated unilaterally, and high in the intact shrimps. The pCO2, [HCO-3] and [HCO-3 + CO2-3] of the haemolymph were low in intact shrimps, intermediate in unilaterally ablated shrimps, and high in bilaterally ablated shrimps. Eyestalk ablation resulted in an increase in the haemocyanin concentration. Haemocyanin concentration was high in the shrimps treated bilaterally, intermediate in the shrimps treated unilaterally, and low in the intact shrimps. Therefore, it is concluded that eyestalk ablation of shrimps causes the concentration of oxy-haemocyanin to increase, the pO2 of haemolymph to decrease, and that it also affects the carbonate buffer system.