Boyer, S. (2012). Ecologie du Copépode Calanoïde Paracartia grani Implication dans le cycle de vie du parasite Marteilia refringens dans la lagune de Thau. [Ecology of the Calanoid copepod Paracartia grani. Implication in the life cycle of the parasite Marteilia refringens in the Thau lagoon.]. Ph.D. Thesis, Université Montpellier, France. 327 pp.

415578

10.1017/s1755267212000565 [view]

Boyer, S.

2012

327 pp.

Publication

Available for editors  

In this study, the life cycle of Paracartia grani, a calanoid copepod belonging to the Acartiidae family was determined in Thau lagoon. Indeed, the copepod involvement in the life cycle of the parasite Marteilia refringens affecting the bivalve productions is suspected. Mesozooplanktonic community was monitored twice a month over two years at a fixed station in the lagoon. Sampling has identified P. grani as the acartiid dominant species in summer. From April to January, the copepod is found in the water column while from February to early April it remains in the sediment as diapausing eggs. The analysis of the population structure (size spectrum, contribution of developmental stages and sex ratio) has revealed that there are in between 6 and 9 generations per year. The study of the influence of three environmental parameters (temperature, salinity and chlorophyll a concentration) on the dynamic nesting species indicated that P. grani egg production was mainly governed by temperature and its rapid increase in spring could trigger the hatching of diapause eggs. The second objective of this study aimed to describe the dynamics of the parasite M. refringens in P. grani, and in the bivalves Mytilus galloprovincialis and Ruditapes decussatus in the Thau lagoon. Histological and in situ hybridization analysis allowed describing the different forms of the parasite in these three species. Research of M. refringens by PCR in P. grani copepodites revealed that the parasite DNA presence in the copepod from June to November, when new mussels appeared infected. Experiments to measure the retention efficiency of the different stages of development of P. grani by mussels have shown that all developmental stages could be involved in M. refringens life cycle, especially copepod eggs that have also shown positive results by PCR. Our study has allowed clarifying interaction between copepod, parasite and mussel but not elucidate completely M. refringens life cycle. Questions remain, especially regarding way of transmission of parasite from copepods to mussels and the potential impact of the parasite on the copepod itself.

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