High parasite diversity in a neglected host: larval trematodes of Bithynia tentaculata in Central Europe.

J Schwelm,N.J Smit,C Selbach,O Kudlai,B Sures

doi:10.1017/s0022149x19001093

Abstract

Bithynids snails are a widespread group of molluscs in European freshwater systems. However, not much information is available on trematode communities from molluscs of this family. Here, we investigate the trematode diversity of Bithynia tentaculata, based on molecular and morphological data. A total of 682 snails from the rivers Lippe and Rhine in North Rhine-Westphalia, Germany, and 121 B. tentaculata from Curonian Lagoon, Lithuania were screened for infections with digeneans. In total, B. tentaculata showed a trematode prevalence of 12.9% and 14%, respectively. The phylogenetic analyses based on 55 novel sequences for 36 isolates demonstrated a high diversity of digeneans. Analyses of the molecular and morphological data revealed a species-rich trematode fauna, comprising 20 species, belonging to ten families. Interestingly, the larval trematode community of B. tentaculata shows little overlap with the well-studied trematode fauna of lymnaeids and planorbids, and some of the detected species (Echinochasmus beleocephalus and E. coaxatus) constitute first records for B. tentaculata in Central Europe. Our study revealed an abundant, diverse and distinct trematode fauna in B. tentaculata, which highlights the need for further research on this so far understudied host-parasite system. Therefore, we might currently be underestimating the ecological roles of several parasite communities of non-pulmonate snail host families in European fresh waters.

Highlights

With about 25,000 species and a cosmopolitan distribution, digenetic trematodes constitute one of the most diverse and ubiquitous groups of parasites on the planet (Esch et al, 2002)
Sequences for the partial 28S rRNA gene and entire ITS1-5.8S-ITS2 gene cluster were generated for one isolate per locality. Both Bayesian inference (BI) and maximum likelihood (ML) analyses of the Cyathocotylidae based on 28S rDNA alignment included novel sequences and those retrieved from GenBank, and resulted in trees with similar topologies
This study examined the parasite diversity in the faucet snail B. tentaculata in Central European fresh waters

Summary

Introduction

With about 25,000 species and a cosmopolitan distribution, digenetic trematodes constitute one of the most diverse and ubiquitous groups of parasites on the planet (Esch et al, 2002) Despite their complex life history with a wide variety of vertebrate definitive hosts, including fish, amphibians, reptiles, birds and mammals, this group shares a unifying character: practically all species require molluscs (usually gastropods) as first intermediate hosts. Trematodes have been shown to make up a large proportion of an ecosystem’s biomass (Kuris et al, 2008; Preston et al, 2013; Soldánová et al, 2016), contribute significantly to the energy flow within ecosystem (Thieltges et al, 2008), function as structuring forces in food webs (Lafferty et al, 2008; Thieltges et al, 2013) and can affect host populations by influencing host mortality, fecundity, growth and behaviour (Mouritsen & Jensen, 1994; Marcogliese, 2004; Lagrue & Poulin, 2008; Rosenkranz et al, 2018) They can serve as useful bioindicators to assess environmental conditions and changes due to their intricate life cycles There is increasing awareness that trematodes are important ecosystem components that require our attention in order to fully understand the complex interactions and dynamics in ecosystems

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Conclusion