JOURNAL OF INVERTEBRATE PATHOLOGY 71,
251-257 (1998) ARTICLE NO. IN974728
Field and Laboratory Studies of
Zebra Mussel (Dreissena polymorpha) Infection by the Ciliate Conchophthirus
acuminatus in the Republic of Belarus
Lubov E. Burlakova,* AlexanderY.
Karatayev,* and Daniel P. Molloy**,1
*Department of General Ecology,
Belarussian State University, 4 Skoriny
Avenue, Minsk, 220050 Belarus; and **Biological Survey, New York State Museum,
Cultural Education Center, Albany, New York 12230
Received July 1, 1997; accepted October 20, 1997
This study quantifies the infection prevalence and
intensity of the European, commensal, host-specific ciliate Conchophthirus
acuminatus (Scuticociliatida: Conchophthiridae) in five zebra mussel
populations within the Republic of Belarus. Laboratory and field experiments
were also conducted to assess variables affecting infection. C. acuminatus was
found in zebra mussels in all five waterbodies sampled: Naroch, Myastro, and
Lukomskoe Lakes, Skema Stream, and in the Svisloch River. Prevalence was always
100%, with the exception of shallow areas (≤0.5 m depth) in the Svisloch
River. This was possibly the result of the elimination of the majority of
infected zebra mussels each winter by a combination of factors, including ice
scour, mallard duck predation, and fluctuating water levels. As a result, zebra
mussels are not permanently present at shallow depths, and the mussels that we
randomly sampled there during the summer were thus smaller (i.e., younger) and
less infected than those present in deeper sections of the river. This is the
first study to quantify the intensity of Conchophthirus infection in
zebra mussels. When infection prevalence was 100%, it was not uncommon for
zebra mussels to have 500-2,000 C. acuminatus in their mantle
cavities, particularly those mussels ca. 15-30 mm in length. Zebra mussels,
while relatively small bivalves, have one of the highest intensities ever
reported for ciliates in the order Scuticociliatida. Infection intensity
correlated directly with mussel length (range in r2 = 0.83-0.92).
Transinfection of zebra mussels with C. acuminatus was achieved
both in the laboratory and field, and represented the first successful trials
to initiate protozoan infection in Dreissena. Laboratory experiments
demonstrated that C. acuminatus rapidly leave their dying zebra
mussel hosts, and this suggested that these mussels are likely a major source
for the spread of C. acuminatus infection. Field trials indicated
that the presence of mussels with high intensity infections can cause an
increase in the levels of infection (both prevalence and intensity) in other
zebra mussels in their microhabitat.
Key Words: Conchophthiridae;
infection prevalence; infection intensity; Dreissenidae.
1 To whom correspondence and reprint
requests should be addressed. Fax: (518) 677 -5236. E-mail: dpmolloy@aol.com.