Mitogenomic characterisation of non-native freshwater snails in Australia: Implications for biosecurity and trematode vector surveillance.

Freshwater snails play essential roles in the transmission of trematode parasites that affect humans, livestock and wildlife. Australia's freshwater ecosystems are increasingly influenced by non-native and potentially invasive snail species that may pose biosecurity challenges and alter parasite transmission dynamics. This study characterised the complete mitochondrial genomes for four non-native snail taxa established in Australia (Pseudosuccinea columella, Orientogalba viridis, Physa acuta and Planorbella sp.) and for Galba truncatula, a high-priority exotic species considered a potential invader. Using long-read sequencing and comparative analyses, 15 complete mitogenomes were assembled, annotated and compared across three families (Lymnaeidae, Physidae and Planorbidae). Genome sizes ranged from 13.7 to 14.3 kb and exhibited conserved gene organisation and marked A + T bias. Australian populations of P. columella, O. viridis and Ph. acuta showed very limited mitochondrial nucleotide variability, consistent with founder effects, demographic bottlenecks and self-fertilisation, in contrast to the marked divergence observed among lineages within Galba from European laboratory strains. Phylogenetic inference based on concatenated and single-gene (cytochrome c oxidase subunit 1, cox1) datasets confirmed well-resolved family-level relationships and revealed cryptic diversity within Galba. The mitogenomes defined here provide molecular references for future taxonomic studies, diagnostic assay development and environmental (e)DNA monitoring of freshwater snails. These genomic resources establish a basis for biosecurity preparedness and vector surveillance in Australia and contribute to a broader One Health approach by supporting early detection, accurate identification and risk assessment of trematode-transmitting snails in freshwater ecosystems.