Pierre Thuet

Effect of copper on survival and osmoregulation of various developmental stages of the shrimp Penaeus japonicus bate (Crustacea, Decapoda)

The object of this study was to evaluate the acute toxicity of cadmium in different post-embryonic stages of the penaeid shrimp Penaeus japonicus (Bate, 1888) and to determine the effect of sublethal cadmium on the osmoregulatory capacity used as an indicator of physiological condition. Tolerance to cadmium increases with the developmental stage. The least tolerant stages are the nauplii (48 h LC50: 124 μg Cd l-1) and the zoeae (96 h LC50: ≃10 to 30 μg Cd l-1). The most tolerant stages are the postlarvae (96 h LC50: ≃200 to 3500 Cd l-1) and juveniles (96 h LC50: 5500 μg Cd l-1). In juvenile shrimp, 2000 μg Cd l-1 significantly reduce hypo- and hyper-OC. The effect of cadmium on hypo- and hyper-osmoregulatory capacity illustrates a dose- and time-dependent response. Surviving shrimp recover their hypo-osmoregulatory capacity after 6 d of readaptation in cadmium-free seawater.

Na+-K+ ATPase and carbonic anhydrase activities in larvae, postlarvae and adults of the shrimp Penaeus japonicus (Decapoda, Penaeidea)

Abstract 1. 1. Activities of Na + -K + ATPase and carbonic anhydrase were measured through the early post-embryonic development of Penaeusjaponicus . In adults, only the Na + -K + ATPase activity was measured. 2. 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. 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. 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. 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. 6. These results are discussed with regard to their ecological and physiological implications. 7. 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. 8. The activity of carbonic anhydrase did not change significantly in larval and postlarval stages. 9. 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.

La régulation osmotique et ionique chez Homarusgammarus (L.) (Crustacea: Decapoda)

Resume Chez Homarus gammarus (L.), des individus juveniles eleves a 15°C supportent sans mortalite des salinites de 17 a 46%.. La regulation est isosmotique dans les milieux de salinite elevee, legerement hyperosmotique en milieu de faible salinite. La regulation des ions Cl−, Na+, K+, Ca2+, et Mg2+, est decrite. La comparaison de ces resultats avec ceux obtenus chez H. americanus H. Milne Edwards fait apparaitre de grandes similitudes.