Éditeur(s) : Elsevier
Résumé : In New Caledonia, the "syndrome 93," which results in mass mortalities of farmed shrimp Penaeus stylirostris, occurs during the transitional and the cold seasons. The transitional season is characterized by an important fall in the average water temperature from 28 to 19 degreesC in 2 weeks. Besides this marked temperature fall, there are also nyctemeral temperature changes of up to 7 degreesC in 12 h. The cold season is characterized by an average water temperature of 19 degreesC with extreme lows of 14 degreesC. The objective of this study was to determine the effect of temperature and its variations on the osmoregulatory capacity of juvenile (7-10 g average weight) and subadult (25 g average weight) shrimps subjected to conditions of different salinity. A reduction in temperature level resulted in a decreased osmoregulatory capacity (OC) (defined as the difference between the osmolality of the haemolymph and that of sea water) at low salinity (hyper-CO) and at high salinity (hypo-CO), respectively, below and above the isoosmotic point (26.2 ppt). In subadult shrimps, the hyper-CO was affected when temperature dropped from 26 to 22 degreesC. The hypo-CO was modified only when temperature decreased down to 15 degreesC. Furthermore, the sensitiveness of osmoregulation to temperature changes was dependent on the developmental stage of the shrimp. Subadults were more sensitive than juvenile animals. The value of the isoosmotic point, which did not depend on the shrimp developmental stage, increased when temperature decreased to 17 or 15 degreesC. Our results provide an additional explanation of the "syndrome 93" and display the unfavourable influence of marked temperature drop on shrimp health. Our research could provide a possibility of seeking a nutritional and/or genetic solution to improve the capacity of the shrimps to maintain their homeostasis within a rearing medium with fluctuating temperatures.
Aquaculture (0044-8486) (Elsevier), 2002-06 , Vol. 209 , N. 1-4 , P. 307-317

Droits : 2002 Elsevier Science B.V. All rights reserved
http://archimer.ifremer.fr/doc/2002/publication-395.pdf
DOI:10.1016/S0044-8486(01)00756-6
http://archimer.ifremer.fr/doc/00000/395/

Éditeur(s) : Elsevier
Résumé : The effect of ambient ammonia and molt stage on the physiological response of the blue shrimp Litopenaeus stylirostris was studied. Shrimps were submitted to 54.6 mg l(-1) ammonia-N (1.76 mg l(-1) NH3-N) for 24 h. Only shrimps in stages C, D-0, D-1 and D-2 were used for the analysis. Haemolymph was assayed for osmoregulatory capacity (OC), magnesium ion (Mg ion), total proteins, oxyhaemocyanin, lactate and glucose. Molt stage had an effect on OC, Mg ion and total proteins in control shrimps, and on OC, Mg ion and lactate in treated animals. Ammonia treatment decreased OC and lactate, and increase Mg ion concentration in haemolymph, for all molt stages. It decreased significantly total proteins and oxyhaemocyanin for stages D-1 and D-2, and increased glucose concentration for stages C and Do. There was a combined effect of treatment and molt stage only on total proteins concentration. The effects of an external factor (ammonia), an internal one (molt stage) and the combination of both, and the usefulness of using physiological parameters measured in this study as tools to detect stress, are discussed. (C) 2004 Elsevier B.V. All rights reserved.
Journal of Experimental Marine Biology and Ecology (0022-0981) (Elsevier), 2004-09 , Vol. 309 , N. 1 , P. 35-46

Droits : 2004 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/2004/publication-371.pdf
DOI:10.1016/j.jembe.2004.03.008
http://archimer.ifremer.fr/doc/00000/371/

Éditeur(s) : Elsevier
Résumé : The effect of ambient ammonia, hypoxia and combination of both on survival and the physiological and immunological response of the blue shrimp Litopenaeus stylirostris in relation to molt stage was studied. Shrimp were submitted to 44.0-71.5 mg 1(-1) total ammonia-N corresponding to 2.0 mg 1(-1) unionized ammonia NH3-N and/or to 1.5 mg O-2 1(-1) (4.3 kPa) for 24 hours. Survival was recorded and the molt stages of both dead and surviving shrimp determined. Only shrimp in intermolt and premolt stages were sampled for analysis of haemolymph. Haemolymph was assayed for osmoregulatory capacity (OC), magnesium ion (Mg2+), calcium ion (Ca2+), total proteins, oxyhaemocyanin, lactate, glucose and total haemocyte count (THC). Low mortalities were recorded for shrimp submitted independently to ammonia or hypoxia. Seventy five percent of dead shrimp were in early post molt (stage A) in ammonia treatment, while hypoxia affected mainly late premolt animals (stage D-2). A synergic effect of ammonia and hypoxia combination (A+ O-2 treatment) on mortality was observed, affecting nearly exclusively shrimp in late premolt stage D-2. Analysis of molt stage repartition at the end of the experiment suggests that ammonia treatment may have accelerated molting. The common physiological response of shrimp to the different treatments was characterized by a reduced OC and an increase in Ca2+. Increase in Mg2+ could not be validated by the statistical analysis, as well as glycaemia variations. Plasmatic lactate level increased and THC decreased in shrimp submitted to hypoxia and the combination of hypoxia and ammonia. Total proteins concentration was reduced in ammonia and A+O-2 treatments. The effect was more pronounced in late premolt shrimp than in intermolt shrimp. Combination of ammonia and hypoxia led to a physiological response stronger than this observed for ammonia-alone and/or hypoxia-alone treatments, except for oxyhaemocyanin. The effects of each external factor (ammonia, hypoxia) and the combination of both, and internal one (molt stage) are discussed. (c) 2007 Elsevier B.V All rights reserved.
Aquaculture (0044-8486) (Elsevier), 2008-02 , Vol. 274 , N. 2-4 , P. 398-407

Droits : 2008 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2008/publication-4092.pdf
DOI:10.1016/j.aquaculture.2007.11.033
http://archimer.ifremer.fr/doc/00000/4092/

Éditeur(s) : Elsevier Science Bv
Résumé : The ontogeny of osmoregulationwas investigated in Litopenaeus stylirostris by studying salinity tolerance and osmoregulatory capacity. Shrimp at different larval and postlarval stages were exposed to various salinities and survival was monitored for 24 h. Survival rates exceeded 80% at salinity over 25 ppt (750 mOsm.kg(-1)) at all the stages. At salinities below to 25 ppt, salinity tolerance was higher in nauplii and zoeae than in mysis larvae. Postlarval stages were able to withstand lower salinities, e.g. 6.0 ppt (176 mOsm.kg(-1)) at PL9 stage, but they were more sensitive than larvae to salinities over 35 ppt (1035 mOsm.kg(-1)). Zoea and mysis larvae slightly hyper-regulated at all tested salinities. After metamorphosis, postlarvae progressively acquired the adult pattern of hyper-hypo-osmoregulation: At PL9, the estimated isosmotic salinity was 24.5 ppt (720 mOsm.kg(-1)); below and over this salinity, animals hyper-regulated and hypo-regulated, respectively. Finally, we determine the effects of lowering salinity at different animal development stages. We conclude that seawater salinity (35 ppt) is optimum during larval stages; but for postlarval stages, lowering salinity at 27 ppt leads to a better growth in 19 days compared to those maintained at 35 ppt (1.07 mg vs 0.47 mg). These results are in agreement with penaeid natural life cycle during which larvae are released in oceanic water while juveniles live in coastal areas where salinity is more fluctuant. (c) 2012 Elsevier B.V. All rights reserved.
Aquaculture (0044-8486) (Elsevier Science Bv), 2012-09 , Vol. 362-363 , P. 10-17

Droits : 2012 Elsevier B.V. All rights reserved
http://archimer.ifremer.fr/doc/00107/21843/20058.pdf
DOI:10.1016/j.aquaculture.2012.07.026
http://archimer.ifremer.fr/doc/00107/21843/

Éditeur(s) : Elsevier
Résumé : The effect of different levels of dissolved oxygen (DO) and a decreased temperature combined with severe hypoxia were studied in the blue shrimp Litopenaeus stylirostris in relation to molt stage. In the first experiment, shrimps were submitted to DO concentrations of 5 to 1 mg l(-1). Osmoregulatory capacity (OC) was measured in shrimps at molt stage C after 6, 24, or 48 h of exposure. No mortality was recorded but a significant negative effect of DO concentration on hypo-OC was observed for DO concentrations below 3 mg l(-1). Osmoregulation improved after 48 h exposure, compared to 6 and 24 h exposure. In a second experiment, temperature was decreased from 28 to 22 degreesC in 24 h, before a severe hypoxia of 0.5+/-0.1 mg O-2 l(-1) was applied. Mortality and OC were studied in relation to molt stages. Half of the shrimps died after respectively 100 min at 0.5 mg O-2 l(-1) at 28 degreesC and 153 min at 0.4 mg O-2 l(-1) at 22degreesC. Mortality was significantly higher in stages D-2 and B compared to stages C and Do. Control shrimps in stage D2 had a lower hypo-OC than shrimps in stages C and Do both at 28 and 22 degreesC. Temperature decrease had no effect on hypo-OC. Hypoxia reduced hypo-OC for all stages, whatever the temperature, but the effect was greater in stage C at 27 degreesC (68% decrease) compared to 22 degreesC (49%) and stage D-2 at both temperatures (respectively, 43% and 58% at 27 and 22 degreesC). Combination of temperature and hypoxia had a significant effect on hypo-OC. Low temperature reduced the effect of hypoxia presumably by slowing down the metabolism. Results are discussed in relation to pond observation. (C) 2004 Elsevier B.V. All rights reserved.
Aquaculture (0044-8486) (Elsevier), 2005-02 , Vol. 244 , N. 1-4 , P. 315-322

Droits : 2004 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/2005/publication-372.pdf
DOI:10.1016/j.aquaculture.2004.11.010
http://archimer.ifremer.fr/doc/00000/372/

Éditeur(s) : Elsevier
Résumé : Penaeid shrimp reared in earthen ponds are exposed to sediment, which can, in some instances, induce a stress. In seawater, the osmoregulatory capacity (hyporegulation) is a useful tool to compare the physiological condition of shrimp exposed to various stressors. By keeping some shrimp in cages at different locations of a single pond heterogeneous in terms of sediment quality, it was possible, using osmotic pressure (OP), to identify some locations where the stress was maximum and some others where it was minimum. Simultaneously, sediment samples were taken and analysed in order to evaluate some physico-chemical parameters that could be related to the stress observed in the shrimps kept in the cages. This approach allowed to show a significant positive correlation between the pH of the sediment surface and the shrimp osmotic pressure. This result was confirmed in a study carried out in experimental 70-1 tanks, where osmotic pressure decreased significantly as water pH decreased from 7.0 to 6.5. The methodology developed in this study may be useful to evaluate the stress caused by sediment in shrimp farms. (C) 2004 Elsevier B.V. All rights reserved.
Aquaculture (0044-8486) (Elsevier), 2004-10 , Vol. 240 , N. 1-4 , P. 297-312

Droits : 2004 Elsevier
http://archimer.ifremer.fr/doc/2004/publication-1866.pdf
DOI:10.1016/j.aquaculture.2004.07.001
http://archimer.ifremer.fr/doc/00000/1866/