The role of trematode parasites in larval anuran communities: an aquatic ecologist’s guide to the major players

Abstract

Conservation strategies depend on our understanding of the ecosystem and community dynamics. To date, such understanding has focused mostly on predator-prey and competitor interactions. It is increasingly clear, however, that parasite-host interactions may represent a large, and important, component of natural communities. The need to consider multiple factors and their synergistic interactions if we are to elucidate the contribution of anthropogenic factors to loss in biodiversity is exemplified by research into present-day amphibian declines. Only recently has the role of factors such as trematode parasite infections been incorporated into studies of the population and community dynamics of aquatic systems. We argue that this is due, at least in part, to difficulties faced by aquatic ecologists in sifting through the complex systematics that pervade the parasite literature. We note that two trematode species are of dominant importance with regard to North American larval anuran communities, and provide in this review a clear explanation of how to distinguish between the infective stages of these two parasites. We describe the general biology and life history of these parasites, as well as what is known about their effect on larval anurans, and the interactive effects of environmental stressors (typically anthropogenic in nature) and parasites on larval anurans. We hope that this review will convince the reader of the potential importance of these parasites to aquatic communities in general, and to amphibian communities specifically, and will also provide the information necessary for aquatic ecologists to more frequently consider the role of these parasites in their studies of aquatic ecology.

Parasite competition hidden by correlated coinfection: using surveys and experiments to understand parasite interactions

“…This pattern likely resulted from the similarity of the parasites' life cycles: both Ribeiroia and echinostomes depend on planorbid snails as first intermediate hosts, amphibians as second intermediate hosts, and birds or mammals as definitive hosts McKenzie 2008, Szuroczki andRichardson 2009). Wetlands conducive to definitive host activity (i.e., visits by frog-eating birds), for example, are more likely to support high abundances of both parasites.…”

“…from field sites and determined their infection status by individually isolating them and examining the water for free-swimming cercariae. Cercariae were examined under a compound microscope to differentiate between Ribeiroia and echinosome parasites (see McKenzie 2008, Szuroczki andRichardson 2009 Although our echinostomes are likely Echinostoma trivolvis, we did not conduct molecular analyses to verify this and refer to them here as ''echinostomes.'' We conducted two experiments to evaluate the effects of Ribeiroia and echinostomes as a function of the timing and dosage of exposure.…”

Metagonimoides oregonensis (Heterophyidae: Digenea) Infection In Pleurocerid Snails and Desmognathus quadramaculatus Salamander Larvae In Southern Appalachian Streams

“…Numerous species within this family, e.g., Echinostoma trivolvis, Echinostoma revolutum, and Echinoparyphium spp., use larval amphibians as second intermediate hosts and can alter tadpole kidney function, and sometimes cause edema, especially in young tadpoles (Schotthoefer et al, 2003;Holland et al, 2007). Studies of both R. ondatrae and echinostomes are appearing more frequently in the ecological literature, in part because they have proved to be useful systems for elucidating general ecological processes underlying disease dynamics in natural systems Szuroczki and Richardson, 2009;Belden and Wojdak, 2011). However, for most of the trematode species that infect amphibians, little remains known beyond basic infection information.…”

Presence of Ribeiroia ondatrae in the developing anuran limb disrupts retinoic acid levels

“…chytrid, ranavirus and parasitism; Collins and Storfer 2003). One particular parasite species, Ribeiroia ondatrae, a digenetic trematode that infects multiple hosts (for a complete review of the life cycle, see Szuroczki and Richardson 2009), has gained worldwide attention as a possible ecological driver behind amphibian declines. This is in part due to the severe and grotesque limb/body malformations caused by infection (Blaustein and Johnson 2003;Johnson et al 1999).…”