Structure and temporal variation of trematode and gastropod communities in a freshwater ecosystem

Abstract

Summary :The infra-and component community dynamics of digenetic trematodes in a freshwater gastropod community were examined over a 33-month period. The gastropod and trematode communities were composed of 17 and 10 species respectively. A total of 9,831 snails was collected; among them, 192 belonging to 14 species were infected by larval trematodes. The size of infected snails was significantly greater than that of healthy ones, and the increase of prevalence with size/age was interpreted as related to the increased probability of ultimately becoming parasitized. The trematode community was rich in allogenic species, but the most frequent trematode (cercariaeum) was autogenic and generalist (a range of 12 snail host species). There was a significantly positive relationship between the frequency of trematode species in the community and the number of first intermediate host species. A great temporal heterogeneity occurred in the prevalence of the snails, mainly attributed to the great temporal fluctuations of snail host populations and the variability of freshwater ecological conditions. The data on the occurrence of larval trematodes in 14 host species over the 33-month study allowed indicate a significant negative correlation between the abundance of gastropods and the prevalence of trematodes.KEY WORDS : trematode, gastropod, communities, dynamics, host-parasite interactions. Resume: STRUCTURE ET VARIATION TEMPORELLE DES COMMUNAUTES DE TREMATODES ET GASTEROPODES DANS UN ÉCOSYSTEME DULCICOLE Afin de mieux comprendre les interactions trematodes-mollusques a I'echelle communautaire, la dynamique des infra-et des xéno-communautés de trématodes digènes d'un lac a été

Infestation of Lymnaea stagnalis by digenean flukes in the Jeziorak Lake

“…Digenean flukes are an important factor regulating populations of their host snails (Thompson 1985;Bayne and Locker 1987;Lauckner 1986;Crews and Esch 1986;Hurd 1990;Lafferty 1993b;Gerard 1997Gerard , 2001a. They can contribute to increased mortality of hosts, especially in highly variable environmental conditions (Theron and Pointier 1995;Gerard 2001b;Morley et al 2003;Azevedo et al 2004).…”

Responses of freshwater molluscs to environmental factors in Southern Brazil wetlands

“…Water hardness, conductivity, pH altitude, substrates (plants), food resources (plants) and biotic interactions have been reported as important environmental predictors of molluscs (Dillon, 2000;Brown, 2001;Gérard, 2001;McMahon and Bogan, 2001;Heino and Muotka, 2006;Sturm, 2007;Horsák et al, 2007). The species-area relationship was not always consistent for wetland molluscs.…”

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

“…In general, the increase in predator pressure and interspecific competition related to the restricted habitat size during drought leads to the elimination of most freshwater gastropods, and new generations typically appear after the water level rises again (Dudgeon, 1982;Gérard, 2001). In small Mediterranean streams characterized by seasonal droughts and floods, P. antipodarum populations are generally incapable of achieving very high densities, and this has been attributed mainly to harsh hydrologic conditions (Múrria et al, 2008).…”

“…As for many invasive species, the successful spread of P. antipodarum is at least partly explained by inadvertent human introductions, but also by the snail's mode of reproduction (i.e., ovoviviparity and parthenogenesis), wide physiological tolerances (e.g., euryhalinity), efficient dispersal, and enemy release (predators, parasites) (Alonso & Castro-Díez, 2008, 2012. In its native range, P. antipodarum is first intermediate host for as many as 20 species of highly host-specific trematodes (Hechinger, 2012), which, as parasitic castrators, generally can substantially impact host populations (e.g., Lafferty, 1993;Gérard, 1997Gérard, , 2001Negovetich & Esch, 2008). In contrast, in Europe, populations are rarely parasitized.…”