The first record of the invasive alien freshwater amphipod Crangonyx floridanus (Bousfield, 1963) (Crustacea: Amphipoda) in two Irish river systems.
We report the presence of the North American Crangonyx floridanus co-occurring with C. pseudogracilis in two Irish rivers, following surveys in three rivers, eleven lake sites and an ornamental pond in 2020. This is the first record of C. floridanus in Ireland which was previously recorded in Britain in 2017. We predict that this species is likely to expand its range through the river and canal connections in Ireland as well as from inadvertent anthropogenic transmission. The taxonomic criteria are cryptic and for this reason, we used genetic methods to distinguish the two species in this study. The results highlight the need to investigate the distribution and impact of these two species in freshwater habitats in Ireland.