Recherches sur la biologie de Bithynia tentaculata linne 1758 : effets de l'échauffement régulier du milieu aquatique sur le cycle biologique de ce mollusque gastéropode prosobranche

Abstract : The life cycle of Bithynia tentaculata has been studied in a natural environment (the Moselle river) and in a particular context of a heated channel. In the latter, the temperature was about 7°C to 10°C higher. Field and laboratory studies were conclued in both environments in order to describe the fecondity, the duration of egg development, the growth, and the sexual maturity. The results demonstrated that under heating conditions, the incubation period was shortened whereas the growth rate increased. As a consequence, the duration of the cyclewas reduced from six months in the Moselle river to four months or even less in the heated channel. Moreover, the absence of a cold temperature period in winter allowed the beginning of the reproduction as early as march instead of may or june in the Moselle river. Consequently, two or three cohorts of Bithynia tentaculata occured during the yaer. Compared to the population of Bithynia tentaculata in the Moselle river, variations of abundance were of lower magnitude in the heated channel. However, the development of the cohort could be limited by some environmental factors, in particular : seasonal parameters remained unchanged (phytoplankton, turbidity, ...) ; due to the temperature of the water during the winter months, numerous predator birds wintering in the area, and most prdator fishes remained active. Z higher rate of mortality might be induced by periods high water temperature during the summer months
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Jean-François Stryjak. Recherches sur la biologie de Bithynia tentaculata linne 1758 : effets de l'échauffement régulier du milieu aquatique sur le cycle biologique de ce mollusque gastéropode prosobranche. Sciences agricoles. Université Paul Verlaine - Metz, 1994. Français. ⟨NNT : 1994METZ066S⟩. ⟨tel-01776856⟩

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