NA+-K+ ATPASE AND CARBONIC-ANHYDRASE ACTIVITIES IN LARVAE, POSTLARVAE AND ADULTS OF THE SHRIMP PENAEUS-JAPONICUS (DECAPODA, PENAEIDEA)

1. Activities of Na+ -K+ ATPase and carbonic anhydrase were measured through the early post-embryonic development of Penaeus japonicus. In adults, only the Na+ -K+ ATPase activity was measured. 2. ATPase activity was variable in the successive development stages. From zero in nauplii, the activity slightly increased in zoeae, and rose sharply in mysis stages 2 and 3. 3. A further significant increase in activity was noted at the transition from late mysis to early postlarvae, concomitant with a change from the larval osmoconforming pattern of osmoregulation to the postlarval and adult hyper-hyporegulating pattern. 4. The activity of Na+ -K+ ATPase, measured in isolated cephalothorax, increased from PL3 to PL4 to its maximum value in PL5; at this stage, osmoregulatory capacity was fully efficient. 5. In young stages of P. japonicus, the variations in Na+ -K+ ATPase activity appear correlated with the development of osmoregulatory ultrastructures, and with osmoregulation and salinity tolerance. 6. These results are discussed with regard to their ecological and physiological implications. 7. In adults, the activity of Na+ -K+ ATPase was high in gills and epipodites and no activity was detected in branchiostegites. These results are related to the ultrastructure of these organs. 8. The activity of carbonic anhydrase did not change significantly in larval and postlarval stages. 9. From these results, it is proposed that the effector sites of osmoregulation are located in branchiostegites, pleurae and epipodites in postlarvae, and in epipodites and mainly in gills in adults.