Objectif
The aim of this project is to provide reliability to hatchery techniques by increasing knowledge on early growth stages of reared bivalves. Actually based on empirical knowledge, commercial hatcheries are developing with more or less success, and face very erratic productions on a seasonal basis.
Gonad maturation processes, control of oocyte maturation, embryogenesis:
In Spain 2 spawning periods were observed for Pecten maximus in February and June. Gonadal development was related to sufficient food in the environment in spring and to the utilization of the stored reserves in muscle and digestive gland in winter. The mean temperature during summer and autumn (18 to 19 C) was too high for gametogenic development, explaining the negative results obtained in the spawning attempts during this period. But these conditions were extremely favourable for good muscular growth.
Optimal concentration of sperm was determined as well as the maximum time for successful fertilization of Mytilus galloprovincialis eggs at different temperatures.
The role of eicosanoids in oocyte maturation in the scallop Pecten maximus was examined and analytical systems were developed to determine the levels of eicosanoids and their precursors in the tissue with special attention to the maturing ovary.
Internal processes of larval development:
Large variability in larval growth performances of P maximus was observed in standard conditions in the experimental hatchery. A biochemical survey in essential nutriments and vitamins was performed during a normal development pattern and compared to other trials. Such variability is partially explained by algal characteristics and more attention should be paid to phytoplankton quality and culture conditions.
Cellular localization of digestive activities was performed in the digestive gland and in the stomach of P maximus. Different rhythms (circadian and seasonal) were evidenced and the effects of substrate and starvation were studied.
Effect of water quality on larval development:
Some microalgae in small quantities in the natural environment went through filters in the hatchery tanks and gave better growth results. One species (a clone of Isochrysis gabana) was isolated and gave better larval performances when added to the classical mixture. Differences in bacterial microflora were also in evidence with positive, neutral or negative effects on larval performances.
The research will be focused on three complementary topics:
Gonad maturation processes, control of oocyte maturation, embryogenesis.
Gonad maturation processes in Ostrea edulis embryogenesis in Mytilus galoprovincialis and comparative studies with Pecten maximus will be performed during this phase as well as the evaluation of the role of eicosanoids and key enzyme processes in oocyte maturation.
Internal processes of larval development.
Biological processes involved after fertilization of the eggs are quite unknown and critical steps are evidenced by non reproducible results observed in hatcheries due to varied survival yields, different growth rates, low success for metamorphosis, difficulties in spat growth. Knowledge of these processes would give a better understanding of the importance of the food characteristics when vitellus storage has been depleted, a better definition of critical stages and requirements. Characterization of normal developmental pattern will be studied by a biochemical and molecular approach in standard rearing conditions.
Effect of water quality on larval development.
Two approaches are planned:
Phenomenological approach: based on reproducible observations in hatcheries that demonstrate significant effect of water quality on growth performances, the phenomena will be studied and origin of such effects will be determined.
Analytical approach: Axenic rearing of larvae and algae has been developed and the effect of varied dissolved organic substances as well as selected bacteria strains can be tested as effectors on larval performances.
Champ scientifique (EuroSciVoc)
CORDIS classe les projets avec EuroSciVoc, une taxonomie multilingue des domaines scientifiques, grâce à un processus semi-automatique basé sur des techniques TLN. Voir: Le vocabulaire scientifique européen.
CORDIS classe les projets avec EuroSciVoc, une taxonomie multilingue des domaines scientifiques, grâce à un processus semi-automatique basé sur des techniques TLN. Voir: Le vocabulaire scientifique européen.
- sciences naturelles sciences biologiques microbiologie bactériologie
- sciences naturelles sciences biologiques microbiologie phycologie
- sciences naturelles sciences de la Terre et sciences connexes de l'environnement hydrologie
- sciences naturelles sciences biologiques biologie du développement
- sciences naturelles sciences biologiques biochimie biomolécule protéines enzyme
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29280 PLOUZANE
France
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