Introduction

The myxosporean Kudoa is a frequently encountered parasite of marine fishes, creating lesions of economic importance in some cases (Lom, 1986). The vegetative stages and the spores which may be contained within pseudocysts, are most frequently reported from the skeletal musculature, but can also infect other tissues and tissue cavities In the course of a recent study of hepatic copper storage in white perch, Morone americans from the Chesapeake Bay, we observed typical quadrate spores of Kudoa We are now investigating the taxonomy and histopathology of the infection.

Review

White perch are present along the Atlantic coast, from the upper St. Lawrence River and southern Gulf of St. Lawrence to South Carolina; inland, freshwater populations are also found (Scott & Scott, 1988). White perch is an abundant species in the Chesapeake Bay, where there is a small commercial fishery. Yet despite common occurrence, there is little information available on parasites and diseases of white perch in its saltwater or brackish water environment (Scott & Scott, 1988). This is in marked contrast to the literature available on parasites of its close relative, the Striped Bass Morone saxatilis in the Chesapeake Bay (Paperna & Zwerner, 1976). Kudoa cerebralis has been reported from the nervous system of striped bass from the Chesapeake Bay (Paperna & Zwerner, 1974).

Kudoa may be encountered in the flesh of fish, where the pseudocysts are often visible to the naked eye. The parasite can also be recognised in tissue sections. Maturation of the spores is frequently accompanied by host response which may consist of inflammation and melanin deposition. Infections in the musculature can cause extensive damage, and some species are associated with breakdown of the host tissue.

Taxonomy of Kudoa is based on the shape and dimensions of the spore which comprises four valves, each containing a polar capsule. In apical view, spores may have a great range of shapes, from approximately square to star-like. In side view, spores may have a simple shape like a loaf of bread, or may be more elaborate. The spores surface can be smooth, or with projections. In the majority of species the four polar capsules are of equal size, the minority of species - have capsules of unequal sizes. Between 30 and 40 species of Kudoa have been described.

Work in Progress

Histological examination of white perch from the Chesapeake Bay has shown that Kudoa sp. infects the musculature and several other sites. Studies are in progress on the morphology and taxonomy of the parasite. and the histopathology of the infection. In addition to the use of hematoxylin and eosin, special stains are being used to improve resolution of the spores.

References

1.  Lom, J. 1986. Protozoan infection in fish. In: Pathology in marine aquaculture (eds. Vivares,C.P., Bonami,J.R. & Jaspers,E.) pp. 95104. European Aquaculture Society, Bredene, Belgium.

2.  Paperna,I. & Zwerner,D.E. 1974. Kudoacerebralia3p.n. (Myxosporidea, Chloromyxidae) from the Striped Bass, Moronesaxatilis(Walbaum). Journal of Protozoology 21 (1), 15-19.

3.  Paperna I & Zwerner,D.E. 1976. Parasites and diseases of striped bass, Moronesaxatilis(Walbaum,) from the lower Chesapeake Bay. Journal of Fish Biology 9, 267 - 287.

4.  Scott,W.B. & Scott,M.G. 1988. Atlantic Fishes of Canada. Canadian Bulletin of Fisheries and Aquatic Sciences #219; 731p.