Variations inter-populations de la structure d'âge et de la croissance du Prosobranche Bithynia tentaculata L.

Abstract

Requ le 19 octobre 1984 VINCENT, B., et C. LETOURNEAU. 1985. Variations inter-populations de la structure d'lge et de la croissance du Prosobranche Bithynia tentaculata L. Can. J. Zool. 63: 1345 -1353. Nous avons CtudiC, dans le Saint-Laurent (Quebec), 25 populations du Prosobranche Bithynia tentaculata afin de mettre en Cvidence les principales variations de leur structure d'lge et de la croissance des diffkrentes generations. Le disCquilibre general des structures d'lge confirme qu'il y a eu, lors d'une annee impaire, un faible recrutement sous I'effet d'une perturbation gknkrale du milieu. La structure d'lge est liee a la temperature, aux sediments et B la vitesse du courant. L'hydrochimie explique une part importante des variations spatiales des longueurs des adultes, mais ces variations ne semblent pas influencer 1'4ge de la maturitk sexuelle. I1 y a un mode possible de regulation des densites par augmentation du taux de croissance des jeunes et donc, par diminution de l'lge de la maturiti sexuelle dans les populations B faibles effectifs; ce mecanisme de regulation semble peu efficace pour compenser une diminution rapide des effectifs ou un desequilibre de la structure d'lge d'une population. Ces risultats et ceux deja publies sur la m2me espece montrent I'importance des facteurs abiotiques pour expliquer les variations spatio-temporelles du profil demographique de ce prosobranche qui a une grande plasticitie phenotypique. VINCENT, B., and C. LETOURNEAU. 1985. Variations inter-populations de la structure d'ige et de la croissance du ProsobrancheBithynia tentaculata L. Can. J. Zool. 63: 1345 -1353. The main variations in age structure and growth of different generations were studied in 25 populations of the prosobranch Bithynia tentaculata in the St. Lawrence River (Quebec). The general unbalanced age structures of the populations reflect a low recruitment encountered during an odd year because of a general disturbance in the environment. The age structure is correlated to temperature, sediments, and current velocity. Water chemistry is largely responsible for the spatial variations in lengths of the adults, but these variations do not seem to influence the age at sexual maturity. Population densities may be regulated by an increase in the growth rate of young which would reduce the age at sexual maturity in populations with low densities; this mechanism would, however, be of little use to compensate a sudden decrease in density or an unbalanced age structure in a population. These results and those of previous studies on this species reveal the important role played by abiotic factors in regulating the spatio-temporal variations of the demographic profile of this prosobranch which possesses a high phenotypic plasticity.[Journal translation]

Evolutionary and physiological adaptations of aquatic invasive animals: r selection versus resistance

“…Bithynia tentaculata endemically ranges from Europe into Asia and northern Africa, where it broadly ranges from stable lakes and rivers to small ponds and streams (Ellis 1969). It is not tolerant of elevated temperatures compared with other freshwater gastropods (Fantin et al 1981;Dregol'skaya and Korotneva 1988), which may explain its high degree of temporal population density variation (Vincent and Létourneau 1985;Subramanian and Thomas 1991). Melanoides tuberculata is native to subtropical and tropical regions of northern and eastern Africa, southern Asia, and Northern Australia, where it inhabits shallow seepages, irrigation channels, pools fed by perennial springs, and lakes (Brown 1980).…”