Unravelling the riddle of Radix: DNA barcoding for species identification of freshwater snail intermediate hosts of zoonotic digeneans and estimating their inter-population evolutionary relationships

Abstract

Please cite this article as: Lawton, S.P., Lim, R.M., Dukes, J.P., Kett, S.M., Cook, R.T., Walker, A.J., Kirk, R.S., Unravelling the riddle of Radix: DNA barcoding for species identification of freshwater snail intermediate hosts of zoonotic digeneans and estimating their inter-population evolutionary relationships, Infection, Genetics and Evolution (2015), doi: http://dx.doi.org/10. 1016/j.meegid.2015.07.021 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. and ITS2 sequences, identified populations of Radix auricularia and R. balthica from specimens originally morphologically identified as R. peregra from the UK. Assessment of cox1 and ITS2 as species identification markers showed that, although both markers differentiated species, cox1 possessed greater molecular diversity and higher phylogenetic resolution. Cox1 also proved useful for gaining insights into the evolutionary relationships of Radix species populations. Phylogenetic analysis and haplotype networks of cox1 indicated that Radix auricularia appeared to have invaded the UK several times; some haplotypes forming a distinct UK specific clade, whilst others are more akin to those found on mainlandEurope. This was in contrast to relationships between R. balthica populations, which had low molecular diversity and no distinct UK specific haplotypes, suggesting recent and multiple invasions from mainland Europe. Molecular techniques therefore appear to be crucial for distinguishing Radix spp., particularly using cox1. This barcoding marker also enables the population biology of Radix spp. to be explored, and is invaluable for monitoring the epidemiology of fluke diseases especially in the light of emerging diseases and food security.

RETRACTED ARTICLE: The complete mitochondrial genomes of two freshwater snails provide new protein-coding gene rearrangement models and phylogenetic implications

“…Meanwhile, the taxonomic position of R. swinhoei should be revised. As pointed out by Lawton et al [46] molecular identification was the only reliable method to identify Radix species and other Lymnaeidae since shell and other anatomical features are morphologically plastic and most species share morphological characters as a result of convergent adaptations to shared limnic environments.

Fig. 6Phylogenomic analysis of concatenated proteins in mitochondrial genomes.

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Comparing direct and indirect selfing rate estimates: when are population-structure estimates reliable?

“…R. balthica is a diploid, simultaneously hermaphroditic freshwater snail that lives in the shallow littoral zone of large water bodies throughout Europe from Iceland to Mediterranean Countries (Cordellier and Pfenninger, 2009;Pfenninger et al, 2011;Lawton et al, 2015). In Lake Zurich, Switzerland, R. balthica hatches from eggs in spring and reaches sexual maturity by the end of the year.…”

“…As the species is phenotypically very variable (see, for example, Brönmark et al, 2011;Schniebs et al, 2011;Ahlgren et al, 2013), the taxonomic identification of Radix snails is notoriously difficult (Pfenninger et al, 2006;Schniebs et al, 2011;Lawton et al, 2015). We therefore verified that only individuals of R. balthica were included in this study by sequencing the mitochondrial cytochrome oxidase subunit I (COI) gene, shown to be well or multilocus (m) inbreeding coefficient; s(g 2 ), mean selfing rate per population estimated using two-locus heterozygosity disequilibrium values, calculated using the software RMES (David et al, 2007); s(PA), mean selfing rate per population estimated based on progeny arrays, either calculated as the proportion of selfed offspring (prop.…”

Complete mitochondrial genome of the radicine pond snail Radix plicatula (Gastropoda: Lymnaeidae)

“…Radix plicatula is a species of aquatic pulmonate gastropod mollusk in the family Lymnaeidae, broadly distributed in China, as well as in Russia (Liu et al 1993). Radix species is one of the intermediate hosts of Fasciola species, which play a critical role in the spread of fascioliasis in humans (Correa et al 2010;Lawton et al 2015). Currently, approximately 20 million people have been infected with fascioliasis worldwide (Correa et al 2010).…”

“…Due to the high plasticity of the shell shape within the Radix species, it is difficult to classify them only according to morphological features (Pfenninger et al 2006;Feldmeyer et al 2010). Recently, some studies have performed the classification and phylogenetic analysis of Radix species and its allies (Bargues et al 2001;Lawton et al 2015;Aksenova et al 2018). So far, however, in Radix only one species (i.e.…”