J. Helminthol. Soc. Wash. 63(2),
1996, pp. 251-256
Research Note
Survey of the Parasites of Zebra
Mussels (Bivalvia: Dreissenidae) in Northwestern Russia, with Comments on
Records of Parasitism in Europe and North America
DANIEL P. MOLLOY1, VITALI A. ROITMAN2,
AND JEFFREY D. SHIELDS3
1 Biological Survey, New York State
Museum, Cultural Education Center, Room 3132, Albany, New York 12230 (e-mail: dmolloy@mail.nysed.gov).
2 Institute of Parasitology, Russian
Academy of Sciences, Leninsky Prospect 33, Moscow 117071, Russia (e-mail: roitman@gelan.msk.su).
and
3 Chesapeake Bay National Estuarine
Research Reserve, Virginia Institute of Marine Science, P.O. Box 1346, Glouster
Point, Virginia 23062 (e-mail: jeff@back.vims.edu)
ABSTRACT: We report the results of a survey of the
parasites of zebra mussels, Dreissena polymorpha, at 13 sites in the
Moscow-St. Petersburg region during 8-22 July 1993. Mussels with trematodes
were observed at 7 (54%) of the sampling sites, with the following prevalence
of infection: adult Aspidogaster, <1 %, at each of 3 sites; Phyllodistomum
sporocysts, <1 %, at each of 4 sites; and Bucephalus polymorphus sporocysts,
9% at 1 site. Severe infections were only noted for B. polymorphus, which
destroyed the gonads of its hosts. Ciliates in the order Hymenostomatida were
observed living inside the digestive gland at 8 (62%) of the sites, with their
prevalence of infection ranging up to 100%. Easily distinguishable from
commensal ciliates in the orders Scuticociliatida and Rhynchodida, which are
found on gills, these ciliates were separable into either a small or large
form. The small ciliate was oblong to round, with a mean length x width of 58 x
45 μm. In contrast, the large ciliate was nearly cylindrical and
had a mean length x width of 278 x 77 μm. Whereas dozens of the
small ciliate could be found in some mussels, the large ciliates rarely
exceeded 10 per host. Whereas both forms were observed moving about in the body
fluid between digestive gland lobes, the small ciliates were also recorded
inside these lobes. The nature of the symbiotic association of these ciliates
remains to be determined.
KEY WORDS: Dreissena, zebra mussels, Aspidogaster,
Phyllodistomum, Bucephalus, trematodes, ciliates.