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Revised Diagnosis, Site of Development, and Lesions Due to Myxobolus hyborhynchi (Myxozoa) Parasitizing Fathead Minnow in Minnesota
Author(s) -
Cone David K.,
Frasca Salvatore
Publication year - 2002
Publication title -
journal of aquatic animal health
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.507
H-Index - 52
eISSN - 1548-8667
pISSN - 0899-7659
DOI - 10.1577/1548-8667(2002)014<0209:rdsoda>2.0.co;2
Subject(s) - anatomy , biology , myxobolus , myxozoa , minnow , basophilic , cartilage , pathology , spore , gill , medicine , botany , fishery , fish <actinopterygii>
Myxobolus hyborhynchi Fantham, Porter, and Richardson, 1939 (Myxozoa) was found to parasitize fathead minnow Pimephales promelas in Minnesota. The parasite formed pseudocysts, primarily in the intraosseous spaces of spongy bone and the cartilage of the head, pectoral girdle, and caudal fin, as well as in perichondral and periosteal connective tissue. A single plasmodium was found in kidney tissue. The fixed spores were oval in frontal view, measured 11–12.5 μm long and 8–9.5 μm wide, and had a length:width ratio of 1:1.15 to 1:1.47. The spores had a distinct posterior mucous envelope; some had a small intercapsular appendix. The polar capsules were almost cylindrical, 5–6.5 μm long and 2.5–3.0 μm wide, with a short terminal end and 5–6 filament coils perpendicular to the capsule axis. Microscopic lesions in cartilage were identified in maxillary and mandibular articulations, gill arches, pectoral girdles, and caudal fins and consisted of focal necrosis, effacement, and replacement by the parasite. Mononuclear inflammatory cells were present in perichondral and periosteal connective tissue foci but were notably absent in areas of cartilage necrosis. Spores dispersed from pseudocysts into surrounding tissues. Small aggregates or isolated spores occurred throughout the pharyngeal mucosa, and intact spores were near the skin surface, a location from which they may be shed. The present study extends the geographic range of M. hyborhynchi from Quebec and Ontario to Minnesota and the host range to fathead minnow. The relationship of M. hyborhynchi to other bone‐invading myxobolids described from North American freshwater fishes will require further comparative studies.