Larval trematode infections in freshwater gastropods from the Albufera Natural Park in Spain

Abstract

Malacological samplings were made from January 1994 to December 1996 in the Albufera Natural Park (Valencia, Spain) to trace the dynamics of molluscan populations and the prevalence and intensity of infection by larval trematodes. A total of 10,533 freshwater gastropods belonging to seven species (Lymnaea auricularia, L. truncatula, L. palustris, L. peregra, Bithynia tentaculata, Physa acuta and Gyraulus chinensis) was examined, and 110 (1.04%) were found to harbour some of the nine distinguishable types of cercariae, namely four echinostome cercariae (Hypoderaeum conoideum, Echinoparyphium recurvatum, Euparyphium albuferensis, and Echinostoma sp.), four furcocercous cercariae, and one xiphidiocercous cercaria. This study shows that the composition of the snail and trematode communities may be determined by the particular environmental conditions present and the human intervention in the area.

Miracidial infectivity of Hypoderaeum conoideum (Trematoda: Echinostomatidae): differential susceptibility of two lymnaeid species

“…Moreover, the observation that the rate of infection obtained under these conditions for L. peregra was identical to that observed in the monomiracidial single-snail exposures suggests that the presence of another susceptible host does not reduce the overall level of parasite transmission and points to a high degree of speci®city in the two-choice experiments. This ®nding agrees with the previous ®eld studies carried out by Toledo et al (1998) Physella acuta 1 ±/20 (0) 3 ±/20 (0) 5 ±/20 (0)…”

“…None of the other gastropod species belonging to other genera became infected, which is in agreement with previous literature (Mathias 1925;Rees 1932;Grabda-Kazubska and Kiseliene 1990;Haas et al 1995b;Toledo et al 1996Toledo et al , 1998. However, an interesting pattern in H. conoideum miracidial infectivity was observed.…”

“…However, in the natural reference habitat of the present study ± the Albufera Natural Park (Valencia, Spain) ± only L. peregra (MuÈ ller, 1774) has been recorded as a natural ®rst intermediate host of this echinostomatid, despite the presence of other lymnaeids (Toledo et al 1996(Toledo et al , 1998.…”

“…Although the diculty of evaluating the correspondence between experimental results and those obtained in the ®eld is recognized, we consider that the preference of the H. conoideum miracidium for L. peregra observed in the laboratory and in the ®eld (Toledo et al 1998) could be due to ecological factors. In this sense, the behavior shown by H. conoideum miracidia could have been the result of a high degree of adaptation to the snail community structure in their natural habitat, where L. peregra is one of the most frequently occurring snail species, whereas L. corvus is less commonly encountered (Toledo et al 1998). Thus, coexistence of the parasite with L. peregra could have led the miracidia to acquire a high degree of speci®city in host location toward this snail species.…”

Interactions related to non-host snails in the host-finding process of Euparyphium albuferensis and Echinostoma friedi (Trematoda: Echinostomatidae) miracidia

“…In addition, Echinostoma friedi miracidia are able to develop in G. chinensis, producing direct competition for the HS of Euparyphium albuferensis. These experimental results could be the explanation for the small number of natural G. chinensis snails found to be infected with E. albuferensis in the Albufera Natural Park (Toledo et al 1998).…”