Abstract

The biodiversity of freshwater ecosystems globally still leaves much to be discovered, not least in the trematode parasite fauna they support. Echinostome trematode parasites have complex, multiple-host life-cycles, often involving migratory bird definitive hosts, thus leading to widespread distributions. Here, we examined the echinostome diversity in freshwater ecosystems at high latitude locations in Iceland, Finland, Ireland and Alaska (USA). We report 14 echinostome species identified morphologically and molecularly from analyses of nad1 and 28S rDNA sequence data. We found echinostomes parasitising snails of 11 species from the families Lymnaeidae, Planorbidae, Physidae and Valvatidae. The number of echinostome species in different hosts did not vary greatly and ranged from one to three species. Of these 14 trematode species, we discovered four species (Echinoparyphium sp. 1, Echinoparyphium sp. 2, Neopetasiger sp. 5, and Echinostomatidae gen. sp.) as novel in Europe; we provide descriptions for the newly recorded species and those not previously associated with DNA sequences. Two species from Iceland (Neopetasiger islandicus and Echinoparyphium sp. 2) were recorded in both Iceland and North America. All species found in Ireland are new records for this country. Via an integrative taxonomic approach taken, both morphological and molecular data are provided for comparison with future studies to elucidate many of the unknown parasite life cycles and transmission routes. Our reports of species distributions spanning Europe and North America highlight the need for parasite biodiversity assessments across large geographical areas.

Highlights

  • In recent years, it has been increasingly uncovered that trematodes commonly complete their life-cycles in freshwaters in the sub-Arctic, using the short summer seasons, with many hosts available at high densities [8, 31, 36, 66, 78, 122]

  • All species found in Ireland are new records for this country

  • Despite the fact that the diversity of echinostomes is relatively well studied in Europe [32, 46], we discovered four species, namely, Echinoparyphium sp. 1, Echinoparyphium sp. 2, Neopetasiger sp. 5 and Echinostomatidae gen. sp. that appear to be novel in Europe and unique to Finland (Echinoparyphium sp. 1, Echinostomatidae gen. sp.), Iceland (Echinoparyphium sp. 2) and Ireland (Neopetasiger sp. 5)

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Summary

Introduction

It has been increasingly uncovered that trematodes commonly complete their life-cycles in freshwaters in the sub-Arctic, using the short summer seasons, with many hosts available at high densities [8, 31, 36, 66, 78, 122]. Trematodes from the family Echinostomatidae are influential players in freshwater ecosystems [81] They can affect the larval trematode component community species composition in snail populations [83, 87], they contribute substantially to energy flow in ecosystems [11], and they can cause diseases in humans and wildlife [43, 130]. They are considered effective competitors in combatting infection with schistosomes as the echinostome rediae actively feed on snail host tissue or other trematodes and can outcompete the less aggressive sporocysts [84]. Echinostomes are frequently being used in ecological studies of host-parasite relationships [25], and they have been favoured in experimental model systems [39, 126]

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