DAO 110:213-225 (2014)  -  DOI: https://doi.org/10.3354/dao02754

Ameson metacarcini sp. nov. (Microsporidia) infecting the muscles of Dungeness crabs Metacarcinus magister from British Columbia, Canada

Hamish J. Small1,*, Gary R. Meyer2, Grant D. Stentiford3, Jason S. Dunham2, Kelly Bateman3, Jeffrey D. Shields1

1Department of Environmental and Aquatic Animal Health, Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Point, VA 23062, USA
2Department of Fisheries and Oceans, Pacific Biological Station, 3190 Hammond Bay Road, Nanaimo, BC V9T 6N7, Canada
3European Union Reference Laboratory for Crustacean Diseases, Centre for Environment, Fisheries, and Aquaculture Science (Cefas), Weymouth Laboratory, Dorset DT4 8UB, UK
*Corresponding author:

ABSTRACT: The Dungeness crab Metacarcinus magister supports a large and valuable fishery along the west coast of North America. Since 1998, Dungeness crabs exhibiting pink- to orange-colored joints and opaque white musculature have been sporadically observed in low prevalence from the Fraser River delta of British Columbia, Canada. We provide histological, ultrastructural, and molecular evidence that this condition is caused by a new microsporidian parasite. Crabs displaying gross symptoms were confirmed to have heavy infections of ovoid-shaped microsporidian spores (~1.8 × 1.4 µm in size) within muscle bundles of the skeletal musculature. The parasite apparently infected the outer periphery of each muscle bundle, and then proliferated into the muscle fibres near the centre of each infected bundle. Light infections were observed in heart tissues, and occasionally spores were observed within the fixed phagocytes lining the blood vessels of the hepatopancreas. Transmission electron microscopy (TEM) revealed multiple life stages of a monokaryotic microsporidian parasite within the sarcoplasm of muscle fibres. Molecular analysis of partial small subunit rRNA sequence data from the new species revealed an affinity to Ameson, a genus of Microsporidia infecting marine crustaceans. Based on morphological and molecular data, the new species is distinct from Nadelspora canceri, a related microsporidian that also infects the muscles of this host. At present, little is known about the distribution, seasonality, and transmission of A. metacarcini in M. magister.


KEY WORDS: Ameson · Crab · Crustacea · Parasite · Microspora


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Cite this article as: Small HJ, Meyer GR, Stentiford GD, Dunham JS, Bateman K, Shields JD (2014) Ameson metacarcini sp. nov. (Microsporidia) infecting the muscles of Dungeness crabs Metacarcinus magister from British Columbia, Canada. Dis Aquat Org 110:213-225. https://doi.org/10.3354/dao02754

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