Phylogenetics of Ichthyophonus parasites

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Ichthyophonus spp. are perhaps the most economically and ecologically important parasites of wild marine fish in the world.

Wild Pacific herring from Puget Sound demonstrating external signs of Ichthyophonus disease

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. (Public domain.)

Ichthyophonus spp. are perhaps the most economically and ecologically important parasites of wild marine fish in the world, based on the recurrence of massive epizootics and associated fish kills. Epizootics are typically attributed to a single species, I. hoferi.  However, ongoing phylogenetic studies are identifying different parasitic genotypes that reflect novel species designations.