An Irish cocktail of flatworm, earthworm and parasite DNAs: genomics of invasive land flatworms (Geoplanidae) reveal infestations by two new Mitosporidium species (Microsporidia).

According to the classical Enemy Release Hypothesis, one reason for the success of invasive species is that they have escaped their predators and parasites during migration to newly invaded territories. In this context, the discovery of any parasite of an invasive species is of particular interest. Here, we report the results of genomic investigations performed on two invasive species of land flatworms (Geoplanidae) collected in Northern Ireland, Kontikia andersoni Jones, 1981, and Australoplana sanguinea (Moseley, 1877). We describe the mitogenomes and paralogous RNA genes of both species. Prey DNA was detected in both flatworm species, providing molecular evidence that their diet includes earthworms. Unexpectedly, we detected sequences assigned to the microsporidian genus Mitosporidium Haag et al., 2015, which, prior to this study, included a single species. Each land flatworm species harboured its own species of Mitosporidium. For nomenclatural reasons, we could not assign binomial names to these species; instead, we designate them as Mitosporidium sp. JL467 (in K. andersoni) and Mitosporidium sp. JL472 (in A. sanguinea). For each new Mitosporidium species, we describe the gene content of the mitogenome and the complete cluster of nuclear ribosomal RNA genes. In the absence of direct evidence of host-parasite relationships, we discuss the possible hosts of these Microsporidia, which could be the flatworms themselves or their prey; the most likely hypothesis is that they are parasites of land flatworms. Other Mitosporidium species should be sought for in native land flatworms from the Australasian region, where the two invasive flatworm species originated. Investigations on the possible pathogenic role of these parasites are needed.