Parasites of Fish from the Great Lakes - Great Lakes Fishery ...

mordax in Lake Erie. Mass mortalities of young-of-the-year and adult O. mordax caused by G.
hertwigi have been reported by Nepszy and Dechtiar (1972) and Nepszy et al. (1978) in Lake
Erie, as well as a similar mortality of adult O. mordax in Lake Ontario (A. Dechtiar, unpublished
data). Dechtiar and Nepszy (1988) stated “We believe that the major contributing factor to these
mortalities was the high prevalence of G. hertwigi.” Nepszy (unpublished data) believed that
infection of O. mordax by G. hertwigi was seasonal, with a peak of infection occurring in the fall,
but fluctuations occurred monthly. Chen and Power (1972), however, did not report any
mortalities of O. mordax infected with G. hertwigi in Lakes Erie and Ontario. Glugea hertwigi
has not been reported from O. mordax in Lakes Michigan, Superior, and Huron. Of the other
microsporans, Glugea cepedianae has been reported to produce large xenomas in the viscera and
cause mortalities in Dorosoma cepedianum (see Putz et al. 1965; Dechtiar 1972a).
Digenetic Trematodes
Of the adult digenetic trematodes, Crepidostomum sp., Acetodextra amiuri, Phyllodistomum spp.,
Sanguinicola occidentalis, and Sanguinicola sp. can be pathogenic to fish if intensities are high
(Davis 1937; Perkins 1951, 1956; Wales 1958b, Gleason et al. 1983). Clinostomum
complanatum, Crassiphiala bulboglossa, Diplostomum flexicaudum, D. spathaceum,
Diplostomum sp., Tylodelphys scheuringi, Uvulifer ambloplitis, Apophallus brevis, Centrovarium
lobotes, Sanguinicola sp., Ichthyocotylurus erraticus, I. pileatus, I. platycephalus,
Ichthyocotylurus sp., Neascus rhinichthys, Neascus sp., and Posthodiplostomum minimum are
larval/immature digenetic trematodes that can be pathogenic to fish in several sites when their
intensities are high (Meyer 1958; Kozicka 1958; Bychovskaya-Pavlovskaya and Petroshevski
1963; Dukes 1975). Smitherman (1968) reported that Lepomis macrochirus fingerlings had a
significant reduction in growth when large numbers (>353) of metacercariae of
Posthodiplostomum minimum were present. Diplostomum spp. can cause lens discoloration and
blindness, and emaciation (Shariff et al. 1980). Diplostomum spathaceum was reported to be the
causative agent of a mass mortality of Perca fluviatilis by Nümann (1972).
Monogeneans
Of the monogeneans, the ancyrocephalids, Dactylogyrus spp., Tetracleidus banghami,
Syncleithrium fusiformis, Diclybothrium armatum, Gyrodactylus spp., Pseudomurraytrema
copulatum, and Tetraonchus moneteron are potentially dangerous parasites to freshwater fish.
They can damage the epithelium of the gills, cause epithelial hyperplasia and excessive mucus
production, and provide portals of entry for secondary fungal infections (Mizelle 1938; Tripathi
1959; Dogiel et al. 1958; Prost 1963; Lester and Adams 1974; Hoffman 1976).
Cestodes
Plerocercoids (larval stages) of the cestodes Triaenophorus nodulosus (in Catostomus
commersonii, Morone chrysops, Perca flavescens), Ligula intestinalis, Schistocephalus sp.,
Proteocephalus ambloplitis, Triaenophorus nodulosus, and T. stizostedionis occurring in the body
cavity, pericardial cavity, mesentery, liver, spleen, and gonads can cause serious problems to
freshwater fish (Esch and Huffines 1973; McCormick and Stokes 1982; Mahon 1976; Sweeting
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