The first report of Hematodinium perezi genotype I infection of Chinese mitten crab (Eriocheir sinensis) from the River Thames, UK.

Hematodinium is a genus of parasitic dinoflagellates which infects marine decapods, including several which are utilised in the global commercial crustacean fishery. Histological screening of the invasive Chinese mitten crab (Eriocheir sinensis) collected from the River Thames UK in 2018 revealed infection by a parasite with features of Hematodinium spp. Molecular analysis of gill tissues from infected crabs confirmed the presence of Hematodinium spp. and more specifically, Hematodinium perezi genotype I, which has previously been reported infecting crustacean species native to the UK (Carcinus maenas and Liocarcinus depurator), including from locations from the nearby English Channel. This is the first report of Hematodinium perezi infecting Chinese mitten crabs in either its native (Asian) or invasive host range. It is proposed that the Chinese mitten crab has acquired this parasite in UK waters subsequent to its introduction several decades ago. This finding is of particular interest for the future aquaculture of this species in its native range since it may indicate susceptibility to infection with Hematodinium perezi genotype II, a parasite prevalent in other crustacean species farmed in Asia. Parasites of the Hematodinium genus have been shown to cause high prevalence infection and disease in numerous farmed and fished crustacean species from around the world and this study marks a confirmed extension of that host range and the potential for Chinese mitten crabs to acquire novel infections within their invasive ranges.