Osmoregulatory capacity according to nutritional status, molt stage and body weight in Penaeus stylirostris

Hypo-osmoregulatory capacity (or hypo-OC, i.e., the difference between the osmolality of the haemolymph and that of sea water), haemolymph glycemia an d haemolymph sodium and chloride concentrations of Penaeus stylirostris wer e studied in experimental tanks according to the size, the molt stage and t he nutritional status of the shrimp. Osmolality and haemolymph glycemia of fed and starved P. stylirostris were also studied in earthen ponds in fluct uating sea water according to time. In experimental tanks, the absolute hyp o-OC of shrimp decreased linearly with increasing wet weight for each molt stage considered. For specimens weighing 16.6 +/- 1.7 g, the absolute hypo- OC was maximum in stage C (217 +/- 17 mosm kg(-1)) and significantly lower in stages B (165 +/- 16 mosm kg(-1)), D-0 (181 +/- 18 mosm kg(-1)), D-1 (14 6 +/- 20 mosm kg(-1)) and D-2 (135 +/- 13 mosm kg(-1)). The hypo-OC and hae molymph glucose concentration varied significantly after the food supply. N o variations in haemolymph sodium and chloride concentrations were observed . In earthen ponds, haemolymph osmolality and haemolymph glucose concentrat ion of molt stage C shrimp increased shortly after the food supply. When sh rimp were kept starved for 24 and 48 h, haemolymph osmolality remained cons tant and haemolymph glucose concentration varied only slightly according to time. In light of these results, the use of shrimp hypo-OC (and/or haemoly mph osmolality) and haemolymph glycemia in aquaculture as potential physiol ogical indicators of disturbance in the aquatic environment is discussed. ( C) 1999 Elsevier Science B.V. All rights reserved.