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Title: POPULATION STRUCTURE AND ENERGETICS OF THE BOPRYID ISOPOD PARASITE ORTHIONE GRIFFENIS IN MUD SHRIMP UPOGEBIA PUGETTENSIS

Author
item SMITH, ANDREW
item CHAPMAN, JOHN
item Dumbauld, Brett

Submitted to: Journal of Crustacean Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/28/2007
Publication Date: 5/31/2008
Citation: Smith, A., Chapman, J., Dumbauld, B.R. 2008. Population structure and energetics of the bopryid isopod parasite orthione griffenis in mud shrimp upogebia pugettensis. Journal of Crustacean Biology.28(2)228-233.

Interpretive Summary: Bopyrid isopods parasitize crab and shrimp hosts and generally cause castration and therefore infertility in the adult host. Orthione griffenis is a species that has been recently found to parasitize mud shrimp in estuaries along the Pacific Coast of North America. These isopods are found in the branchial chamber of these shrimp where they suck blood as it passes from the gills to other organs, but the actual effects on host weight loss are little studied. We sampled a population of shrimp in Yaquina Bay, Oregon which were heavily parasitized by this isopod (80% of large reproductive females infested). We measured weights of both parasitized and un-parasitized shrimp and found that weight loss due to the parasite is related to the weight and size of the parasite, but the relationship is highly variable. We found clear evidence that the ability of adult female shrimp to reproduce is severely compromised, but it appears that the effect on male shrimp and the shrimp population as a whole may be more substantial. The high prevalence of these isopods in current shrimp populations and positive correlation between isopod presence and host weight loss indicate potentially large impacts to shrimp populations along the coast.

Technical Abstract: The population structure and energetic burden of bopyrid isopod parasite Orthione griffenis on the eastern Pacific mud shrimp Upogebia pugettensis are estimated from size and weight relationships between parasite and host. U. pugettensis weight loss increases with O. griffenis weight but the high variance in the relation indicates that direct weight comparisons are insufficient to reveal most of the host-parasite energetic interactions. Environment, reproductive development, age, molt stage and the feeding histories of the hosts and parasites, not apparent from simple weight ratios, are likely to be important factors in their interaction. The high prevalence of O. griffenis among U. pugettensis and positive correlation between host weight loss and parasite weight nevertheless, indicate large impacts of these parasites on mud shrimp populations are occurring with corresponding effects on estuarine dynamics in Pacific Northwest estuaries.