Éditeur(s) : HAL CCSD National Shellfisheries Association
Résumé : International audience
Monitoring gonad maturation for protandrous and functional hermaphrodite species such as the giant clam Tridacna maxima is difficult due to the juxtaposition and relative proportion of male and female tissues in the gonad [gonadal sex ratio (GSR)]. Here, the relevance of the widely used gonadosomatic index (GSI) as proxy of giant clam gonad maturation is tested with a large dataset (n ¼ 265). Gonadosomatic index is compared with other indices, namely the proportion of the male part harboring spermatozoids, the proportion of empty oocyte follicles, the mean oocyte diameter, and the oocyte elongation. At gonad scale, high index variability highlighted partial spawning. At individual scale, male and female maturation proxies were contrasted, showing either asynchronous emissions of male and female gametes or contrasted spermatogenesis and oogenesis duration. The GSI was mostly driven by the number and diameter of oocytes and therefore it is recommended here as primary proxy for female maturity. Except for the oocyte elongation, all indices were affected by the GSR, which ruled out drawing conclusions at population scale. These results highlight the need for maturation stage proxies that are optimized for functional hermaphrodite species.
ISSN: 0730-8000

hal-01613648
https://hal.archives-ouvertes.fr/hal-01613648
https://hal.archives-ouvertes.fr/hal-01613648/document
https://hal.archives-ouvertes.fr/hal-01613648/file/Gaertner-Mazouni-2016-eio.pdf
DOI : 10.2983/035.035.0107

Éditeur(s) : Elsevier Science Bv
Résumé : In bivalve aquaculture, dominant fouling organisms are filter feeders which can compete for food with reared bivalves, sometimes causing mortality or reducing their growth rate. This study investigated the effect of biofouling on the farmed pearl oyster Pinctada margaritifera in two lagoons of French Polynesia. Survival, growth and reproduction of 2 year-old pearl oysters were monitored with regular sampling schedules, from the initial stage of colonization up to 20 months of biofouling accumulation. Control groups of pearl oysters were kept free of biofouling as is the current practice in pearl farms. After more than a year of monitoring, no significant difference was recorded in shell growth rate between pearl oysters reared with epibionts and the control group of pearl oysters, at both sites. Mean annual shell growth rate (height) was 30.5 ± 9.2 mm in Tahiti and 24.8 ± 7.7 mm in Mangareva. Neither the survival nor the reproduction indices were negatively affected by biofouling. In Mangareva, where biofouling development was quantified during 1 year, the rate of colonization appeared to be high during the first 3 months before slowing down. These results raise questions about the necessity of removing biofouling at this stage of pearl oyster production (i.e. before grafting).
Aquaculture (0044-8486) (Elsevier Science Bv), 2014-10 , Vol. 434 , P. 18-26

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00201/31188/29587.pdf
DOI:10.1016/j.aquaculture.2014.07.012
http://archimer.ifremer.fr/doc/00201/31188/

Éditeur(s) : Inter-Research
Résumé : Experimental infections of Penaeus (Litopenaeus) stylirostris were performed with a Vibrio penaeicida strain (AM101) isolated in New Caledonia from Syndrome 93 diseased shrimp. Cumulative mortalities resulting from intramuscular injection or immersion of shrimp in bacterial suspensions demonstrated high virulence for this bacterial strain and suggested that V. penaeicida could be the etiological agent of Syndrome 93. The median lethal dose (LD50) for AM101 was 1.3 x 104 CFU (colony forming units) ml-1 by immersion and less than 5 CFU shrimp-1 by intramuscular challenge, with mortality outbreaks at 48 and 22 h after challenge, respectively. A polymerase chain reaction (PCR) detection assay using a primer set designed from the 16S ribosomal RNA gene of V. penaeicida was developed. It gave an expected amplicon of approximately 310 bp in ethidium bromide-stained agarose gels. The specificity of these primers was assessed with different Vibrio species. Furthermore, DNA extracted by the ChelexTM method could be used to detect fewer than 20 cultured Vibrio cells in seawater or shrimp hemolymph by this assay. It appears to be a reliable screening method for detecting V. penaeicida in shrimp and from the aquatic environment.
Diseases of aquatic organisms (0177-5103) (Inter-Research), 2000-03 , Vol. 49 , N. 2 , P. 109-115

Droits : Inter-Research 2000
http://archimer.ifremer.fr/doc/2000/publication-4436.pdf
DOI:10.3354/dao040109
http://archimer.ifremer.fr/doc/00000/4436/

Éditeur(s) : Universidad Autonoma de Baja California
Résumé : The pathogenicity of two V. penaeicida strains, AM101 and KH-1, with different geographic origin, and V. nigripulchritudo strain AM102, were investigated in juvenile blue shrimp species Litopenaeus stylirostris. Alive bacteria and protein fractions (PFs) obtained from cell-free supernatants (CFS) were used in experimental challenges. Strains AM102, AM101, and KH-1 produced respectively 60, 54 and 12% mortality at 96h after infection using 104 cfu mL-1 of bacterial suspension. Exocellular toxin-like factors were evidenced in CFS from the New Caledonian strains (AM102 and AM101) but not the Japanese strain (KH-1). At 48h post injection of each CFS, mortality rates were respectively 96,98 and 5% when these strains were cultivated at 20°C, whereas only O,16 and 5% mortality rates were observed when these strains were cultivated at 30°C. Clear differences in pathogenicity between both V. penaeicida strains of distinct geographic origin (AM101 and KH-1) were thus emphasized. Protein fractions were obtained from CFS of all the strains tested in this study and cultivated at 20°C, by ammonium sulphate precipitation. Whatever the used strain, significantly higher mortalities were produced with PFs obtained with 0-40% of ammonium sulphate saturation, in respect to those produced with PFs60 and PFs80. Shrimp injected with PFs40 from strains AM102, AM101 and KH-1, and at a 20-µg org-1 dose produced respectively 100, 90 and 60% mortality 46h after the challenge. The strain AM101 showed a mediam lethal dose of approximately 5µg protein org-1 (1-1.25 µg protein g-1 body weight) 59h after injection. The PFs40 from New Caledonian strains were fond sensitive to heating and proteinase K treatments, reinforcing thus the hypothesis of their proteinaceous nature. Surprisingly, PFs40 from each bacterial strain displayed similar protein bands by SDS-PAGE suggesting that the tested strains share a common exotoxic compound regardless their distinct geographic origin or species.
Ciencias Marinas (Universidad Autonoma de Baja California), 2003 , Vol. 29 , N. 1 , P. 77-88

Droits : Universidad Autonoma de Baja California
http://archimer.ifremer.fr/doc/2003/publication-2807.pdf
http://archimer.ifremer.fr/doc/00000/2807/

Résumé : Tahiti’s pearl farming industry plays a major socio-economic role in French Polynesia. In an increasingly competitive market where the production of high quality pearls becomes essential, research can help secure and ensure sustainable production. In that context, Ifremer, in close collaboration with the “direction des resources marines” (French Polynesian government agency) has developed research projects on the “sustainable development of pearl farming”. This program is organized along 3 axes: (1) understanding the animal physiology and initiating a genetically selective breeding program of donor oysters; (2) understanding pearl oyster larvae dispersal and recruitment; (3) understanding the molecular mechanisms underlying biomineralization processes during shell and pearl formation. It is in this frame that we have developed a highthroughput Expressed Sequence Tags pyrosequencing program on the calcifying mantle, combined with proteomic analyses of the shell and pearl. We analyzed 276738 EST sequences, leading to the constitution of a P. margaritifera mantle transcripts catalogue of 82 sequences potentially involved in biomineralization. Our results provided direct evidence that our ESTs data set covers a large number of the matrix proteins of P. margaritifera. In addition, our proteomic analysis enabled us to retrieve, in silico, all the sequences from P. margaritifera involved in the biomineralization process already published on databases. Integration of these two methods allowed, for the first time, the global composition of calcifying tissue and calcified structures to be examined in tandem.
Recent Advances in Pearl Research—Proceedings of the International Symposium on Pearl Research 2011.Edited by Shugo Watabe, Kaoru Maeyama and Hiromichi Nagasawa. 2013. ISBN : 978-4-88704-158-5. pp.184-194

Droits : 2013 TERRAPUB. All rights reserved.
http://archimer.ifremer.fr/doc/00167/27840/26049.pdf
http://archimer.ifremer.fr/doc/00167/27840/