An introduced Asian parasite threatens northeastern Pacific estuarine ecosystems

The introduced Asian parasitic bopyrid isopod, Orthione griffenis, was first discovered on the Pacific coast of North America in Washington in 1988 and next in California in 1992. The range of Orthione presently extends from British Columbia to Baja California, where it infests at least two species of the native estuary mud shrimp, Upogebia. Intense Orthione infestations are associated with the apparent demise of many local populations of Upogebia pugettensis yet nonindigenous origins of Orthione in North America and thus the ecological significance of its impacts have remained in doubt. Six criteria reveal that Orthione is introduced to North America: its conspecificity with disjunct Asian populations, its earliest (1950s) collections in Asia, its late discovery among symbiotic species associated with Upogebia, its historical absence, and its appearance in North America coincident with extensive new ballast water traffic from Asia. Orthione is the first recognized bopyrid isopod invasion globally. Coexistence of U. pugettensis, which are ecosystem engineers, with its newly acquired parasite cannot be assumed. Orthione threatens eastern Pacific estuary ecosystems where Upogebia were previously abundant.