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Marrowstone Marine Field Station

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Disease Ecology Research at the Marrowstone Marine Field Station


Ichthyophonus hoferi is a member of the Mesomycetozoea, a monophyletic class of protozoans that includes several other pathogenic organisms. Currently I. hoferi and I. irregularis are the only two recognized species in the genus, but other species have likely been grouped with I. hoferi based on the plasticity of morphological characteristics. Additional molecular phylogenetic studies are necessary to better understand the relatedness of I. hoferi isolates; therefore, we refer to the organism generically as Ichthyophonus. From 1898 through the mid 1950’s, six major Ichthyophonus-related epidemics occurred in Atlantic herring (Clupea harengus) from the Western North Atlantic. More recently, a massive Ichthyophonus-related epidemic killed an estimated 300 million Atlantic herring in waters around Sweden and Denmark during the early 1990’s and epidemiological data implicate Ichthyophonus as a primary factor responsible for mortality in wild Pacific herring (Clupea pallasii) from estuarine waters of Washington State.

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photo of herring with Ichthyophonus

Wild Pacific herring from Puget Sound demonstrating external signs of Ichthyophonus disease. Note the presence of pigmented, black ulcers on the flank where Ichthyophonus spherical bodies ruptured through the skin.

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