Population dynamics and life cycle of Pisidium amnicum (Müller) (Bivalvia : Sphaeriidae) and Valvata piscinalis (Müller) (Gastropoda : Prosobranchia) in the Saône river, a nine-year study

Abstract

The population dynamics and life cycle of two mollusc species Pisidium amnicum and Valvata piscinalis of the Saône river were studied for nine years. The newborn of the former species appeared in April each year. The latter species produced two cohorts per year until 2003. Spawning in spring led to the birth of the early cohort, which generally appeared in May, while spawning in the summer led to the birth of the late cohort, which appeared from July to November. The increase of the mean annual temperature by 1.9°C from 1998 to 2000 was followed by an increase in the density of mollusc populations, possibly triggering or amplifying inter and intra specific competition for food. However, the 2003 heatwave was responsible for the sudden decline of the P. amnicum population, then the more progressive decline of that of V. piscinalis after having strongly modified its demographic structure and its life cycle. In 2004 and 2005 V. piscinalis only produced one cohort per year. The observations carried out strongly suggest that the insufficiency of available resources was one of the possible causes of their failure to recover in 2004 and 2005. The increase of global warming predicted by different models could result in the gradual disappearance of P. amnicum from the potamon and of V. piscinalis from the freshwater systems most directly exposed to climatic warming, such as the Saône River.

Diel activity cycles of freshwater gastropods under natural light: Patterns and ecological implications

“…2 and 4) also suggest poor competitive abilities, a hypothesis consistent with Mouthon and Daufresne's (2008) view that this species has failed to recover from acute thermal stress because of high competition for post-disturbance limited food resources. Low in situ abundance of the otherwise common V. piscinalis in central Italian lakes (Mastrantuono and Mancinelli, 2005; authors' personal observations), may be similarly related to poor competitive abilities, but specific studies are needed to verify this hypothesis.…”

“…Water temperature and pH remained within the relatively narrow ranges of y16-20 xC and 7.9-8.3 units, respectively. Such ranges are unlikely to influence the biology of any of the snail species investigated (Hodasi, 1976;Girod et al, 1980;Costil, 1994;Mouthon and Daufresne, 2008; and authors' personal observations); therefore, water temperature and pH are not treated further in this study.…”

“…Except for Valvata piscinalis which is negatively affected by water temperatures above y23-25 xC (Burgmer et al, 2007;Mouthon and Daufresne, 2008), all species are adapted to warm (temperature y25-32 xC), relatively oxygen-poor, and/or eutrophic waters (Berg and Ockelmann, 1959;Girod et al, 1980;Costil, 1994;Ferreri, 1995;authors' personal observations). All species are herbivorous on periphyton and/or detritus (Brown, 2001;Lombardo and Cooke, 2002;Mouthon and Daufresne, 2008); bithyniids and valvatiids may also filter-feed on suspended particles (Kabat and Hershler, 1993;Mouthon and Daufresne, 2008). Nomenclature follows Dillon et al (2002) for Physa (= Physella) acuta and Bank (2007) for all other species.…”

Lithoglyphus naticoides (Pfeiffer) (Gastropoda: Prosobranchia): distribution in France, population dynamics and life cycle in the Saône river at Lyon (France)

“…quences have been dramatic for mollusc communities (Mouthon & Daufresne 2006, 2007. Lithoglyphus generally spawn on the shells of their congeners.…”

Long-term population fluctuations of the exotic New Zealand mudsnail Potamopyrgus antipodarum and its introduced aporocotylid trematode in northwestern France

“…More precisely, the rapid increase (Kilgour & Mackie, 1988). Moreover, Sphaeriidae can survive both temporary air exposure and freezing of the sediment they inhabit (Jurkiewicz-Karnkowska & Zbikowski, 2004;Kubíková et al, 2011), yet may perform poorly at increased temperatures [e.g., the declines of Pisidium amnicum in the French Saône and Iberian Minho Rivers during heat waves (Mouthon & Daufresne, 2008;Sousa et al, 2011)]. This all suggests that the substantially lower mean and minimum water temperatures and lower depths may have favored the population performance of Sphaeriidae in Le Petit Hermitage, and disfavored the population performance of P. antipodarum.…”