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Can an introduced specialist parasitic castrator eliminate its host?
Chapman, J. W., B. DUMBAULD, AND T. H. DEWITT. Can an introduced specialist parasitic castrator eliminate its host? Presented at 6th International Conference on Marine Bioinvasions, Portland, OR, August 24 - 27, 2009.
Griffen's isopod, Orthione griffenis was probably introduced to North America with ballast water from Asia in the 1980’s and is the first introduced bopyrid to be recognized anywhere in the world
Griffen's isopod, Orthione griffenis was probably introduced to North America with ballast water from Asia in the 1980’s and is the first introduced bopyrid to be recognized anywhere in the world. Orthione griffenis is also one of the first obligate marine species introduced to the eastern Pacific. Blood loss due to O. griffenis infestations effectively castrates females of its new native host, the blue mud shrimp, Upogebia pugettensis. O. griffenis has been found in every Upogebia population examined between Morro Bay, California and Bamfield, British Columbia. Moreover, since O. griffenis’ arrival, dramatic declines or local extinctions have occurred in all U. pugettensis populations examined. These population declines and extinctions and the apparent broad scale prevalence of Orthione indicate Upogebia could be threatened by this new invader. The threat also appears likely from the host-parasite interactions. Density-dependent effects are assumed to control outcomes in most epidemiological, stock assessment and propagule pressure models involving specialist parasites. Specialist parasites are expected to decline to low abundances or extinction as host populations decline and then hosts are expected to recover. These conditions do not appear to occur with this new invader. Orthione locates Upogebia even at extremely low densities and persists in reservoirs of sterile old hosts, from where its production of infective propagules appears to limit or eliminate Upogebia reproduction over multiple generations. This non-coevolved parasite thus appears capable of eliminating its new host and thence itself.