Mytilicola orientalis

In a naturally infected population of pacific oysters 14% of the oysters were infected, with up to 20 M. orientalis in one oyster.^[7]

The diet of this parasitic species in the blue mussel host consists of both host tissue and organic material in the gut of the host.^[5] The latter means that in some respects the species can be seen as a commensal and does not have to negatively impact its host.^[7]

Females are often larger than males.^[5]

Mytilicola orentalis originates in the Japanese Sea^[4] and is known to occur on the Pacific coast of the United States and Europe.^[8]

Since its introduction in Europe it has been observed across European waters, including locations in France, Ireland, the United Kingdom and the Netherlands.^[4][8] Although this is a marine species, it has been observed in mussels in brackish water in the Kiel bay.^[6]

Host species in the native range include a wide variety of bivalve species. These include, but are not limited to, Barnea dilatata japonica,^[9] Barnea manilensis,^[9] the blue mussels,^[4] the Mediterranean mussel,^[2] the pacific oyster,^[4] the European flat oyster,^[2] and the Japanese carpet shell.^[4]

Mytilicola orentalis infection in pacific oysters correlates with the co-infection with Polydora sp.^[7] In the Mytilida co-infections between M. orientalis and M. intestinalis sometimes occur.^[2]