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Diseases of Aquatic Organisms

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DAO 41:31-36 (2000)  -  doi:10.3354/dao041031

Ichthyophonus irregularis sp. nov. from the yellowtail flounder Limanda ferruginea from the Nova Scotia shelf

Thomas G. Rand1,*, Kelly White1, Jamie J. Cannone2, Robin R. Gutell2, Colleen A. Murphy3, Mark A. Ragan3,4

1Biology Department, Saint Mary¹s University, Halifax, Nova Scotia B3H 3C3, Canada
2Institute for Cellular and Molecular Biology, University of Texas, Austin, Texas 78712-1095, USA
3Institute for Marine Biosciences, National Research Council of Canada, 1411 Oxford St, Halifax, Nova Scotia B3H 3Z1, Canada
4Canadian Institute for Advanced Research, Program in Evolutionary Biology, 180 Dundas Street West, Suite 1400, Toronto, Ontario M5G, 1Z8, Canada

ABSTRACT: A previously described unusual form of the protistan parasite Ichthyophonus, differing in morphological and developmental features from I. hoferi sensu Plehn & Mulsow, was recovered from yellowtail flounder Limanda ferruginea Storer from the Brown¹s Bank area of the Nova Scotia shelf. The nuclear gene encoding the rRNA of the small ribosomal subunit was amplified from this unusual form of Ichthyophonus using the polymerase chain reaction, sequenced and aligned with other eukaryote small subunit (ssu)-rDNAs. Inferred phylogenetic trees clearly show that its ssu-rDNA is distinct from those of 2 isolates of I. hoferi sensu Plehn & Mulsow from different hosts and geographical locations (herring in the North Sea, and yellowtail flounder from the Nova Scotia shelf). We consider the unusual form to be a separate species, I. irregularis. The occurrence of a second, distinct type of Ichthyophonus within a single host species raises the possibility that ichthyophoniasis could be produced by different (although related) pathogens, and in some cases, by concurrent infections of the two.

KEY WORDS: Ichthyophonus hoferi · Ichthyophonales · Ichthyophoniasis · Limanda ferruginea · Ssu-rDNA · Phylogeny

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