Malacological survey in a bottle of water: A comparative study between manual sampling and environmental DNA metabarcoding approaches

Abstract

27To assess the effect of anthropogenic activities on ecosystems, it is of prime importance to 28 develop new tools enabling a rapid characterisation of ecological communities. Freshwater 29 ecosystems are particularly impacted and threatened by human activities and need thorough 30 attention to preserve their biodiversity and the ecological services they provide. Studying such 31 ecosystems is generally difficult because the associated organisms are hard to sample and to 32 monitor. We present a ready to use environmental metabarcoding diagnostic tool to 33 characterise and monitor the freshwater malacofauna from water samples. The efficiency of 34 this new tool was compared to a classical malacological survey at 19 sampled sites from 10 35 distinct rivers distributed over Corsica Island (France). Our eDNA monitoring tool 36 demonstrated a remarkable ability to reconstitute the local malacofauna compared to the 37 malacological survey, with 97.1% of species detection confirmed by both methods. The 38 present tool successfully detected the 11 freshwater snail species previously reported in 39Corsica by malacological survey but was limited at the genus level for some species. 40Moreover, our malacological survey allowed an update of the local distribution of a wide 41 diversity of freshwater snails including invasive species (i.e. Potamopyrgus antipodarum and 42Physa acuta) as well as snail hosts of pathogens of medical and veterinary importance (i.e. 43Bulinus truncatus and Galba truncatula). 44 45

Make visible the invisible: Optimized development of an environmental DNA metabarcoding tool for the characterization of trematode parasitic communities

“…According to our sampling design, the eDNA approach appeared more powerful than classical trematode surveys to detect trematodes established locally. This result echoes with those generally obtained in empirical studies that compare classical prospections and eDNA approaches (Deiner et al, 2017; Hänfling et al, 2016; Mulero et al, 2021; Valentini et al, 2016). However, we believe that this particularly holds for trematodes given their complex life cycles and the difficulty to detect them in natura .…”

“…Phenogram illustrating the relationships between trematode species based on the percentage of nucleotide differences between the metabarcode sequences. The numbers on each branch indicate the percentage difference in nucleotides between sequences obtained in empirical studies that compare classical prospections and eDNA approaches (Deiner et al, 2017;Hänfling et al, 2016;Mulero et al, 2021;Valentini et al, 2016). However, we believe that this particularly holds for trematodes given their complex life cycles and the difficulty to detect them in natura.…”

“…N is the total number of mollusks sampled. Nseq is the total number of sequences successfully affiliated with trematodes at each site obtained in empirical studies that compare classical prospections and eDNA approaches (Deiner et al, 2017;Hänfling et al, 2016;Mulero et al, 2021;Valentini et al, 2016). However, we believe that this particularly holds for trematodes given their complex life cycles and the difficulty to detect them in natura.…”