Determination of gender in the pearl oyster pinctada margaritifera Auteur(s) : Chavez-villalba, Jorge Soyez, Claude Huvet, Arnaud Gueguen, Yannick Lo, Cedrik Le Moullac, Gilles Éditeur(s) : Natl Shellfisheries Assoc Résumé : The pearl industry in French Polynesia is based on exploitation of natural stocks of the black-lip pearl oyster (Pinctada margaritifera); it generates an annual turnover of 90 million euros. Improvements in pearl quality need genetic studies to improve the populations. This pearl oyster is a protandric species, where the sex-ratio normally is biased towards males. There is an increasing interest in gender control to find the mechanisms to augment female proportions for management purposes. This review summarizes information on exogenous and endogenous factors regulating gender in this and other bivalves and concludes that P. margaritifera is a protandric hermaphrodite, developing as a male during the first two years and without evidence of an effect from abiotic and biotic factors on gender during this phase. Later, pearl oysters progressively change to females, reaching a sex ratio close to 1:1 in specimens >8 years; at this stage, gender is apparently influenced by environmental parameters, but particularly by stress. Future research should seek to accurately determine the effect of temperature and food on sex ratios. Studies should be performed to characterize genes responsible for expression of gender. The use of hormones is a path that might be explored to influence the gender of pearl oysters. Journal Of Shellfish Research (0730-8000) (Natl Shellfisheries Assoc), 2011-08 , Vol. 30 , N. 2 , P. 231-240 Droits : info:eu-repo/semantics/openAccess http://archimer.ifremer.fr/doc/00040/15100/12543.pdf DOI:10.2983/035.030.0206 http://archimer.ifremer.fr/doc/00040/15100/ | Partager |
Physiological responses of female and male black-lip pearl oysters (Pinctada margaritifera) to different temperatures and concentrations of food Auteur(s) : Chavez-villalba, Jorge Soyez, Claude Aurentz, Hermann Le Moullac, Gilles Éditeur(s) : Edp Sciences S A Résumé : This study was designed to measure responses of four-year-old black-lip pearl oysters (Pinctada margaritifera) to different temperatures and food concentrations and to identify the energy requirements of each sex. Oysters were fed a monospecific microalgal diet of Isochrysis affinis galbana (T-iso). Measurements of oxygen consumption and ingestion rates were carried out at 24 degrees C and 27 degrees C and at two algal (T-iso) concentrations: 5000 and 30 000 cell ml(-1). Glycogen content in adductor muscle, absorption efficiency and scope for growth were also estimated. Females and males responded differently to environmental factors, with food level being the most influential parameter. Oxygen consumption and absorption efficiency were significantly higher in females than in males, but males had significantly higher glycogen content than females. At high food concentration, glycogen content, ingestion rate, oxygen consumption, and scope for growth were significantly higher than at the low food concentration. Only absorption efficiency was significantly higher at the low food concentration. Oxygen consumption was significantly higher at 27 degrees C than at 24 degrees C. These results indicate that females and males have different bioenergetic functioning and that energy demands for reproduction are higher in females. Aquatic Living Resources (0990-7440) (Edp Sciences S A), 2013-07 , Vol. 26 , N. 3 , P. 263-271 Droits : EDP Sciences, IFREMER, IRD 2013 http://archimer.ifremer.fr/doc/00157/26855/24980.pdf DOI:10.1051/alr/2013059 http://archimer.ifremer.fr/doc/00157/26855/ | Partager |
Response of the blue shrimp Litopenaeus stylirostris to temperature decrease and hypoxia in relation to molt stage Auteur(s) : Mugnier, Chantal Soyez, Claude 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/ | Partager Voir aussi Temperature Stress Penaeid shrimp Osmoregulation Molt stage Litopenaeus stylirostris Hypoxia Télécharger |