02175nas a2200217 4500008004100000245010900041210006900150300001400219490000700233520145600240653001401696653003001710653002501740653002101765653001701786100002201803700002201825700001901847700002201866856006901888 2007 eng d00aDreissena polymorpha and Conchophthirus acuminatus: What Can We Learn from Host-Commensal Relationships?0 aDreissena polymorpha and Conchophthirus acuminatus What Can We L a1153-11600 v263 a

Host specificity, extremely high prevalence and infection intensity, and easy sampling make the mantle-cavity ciliate Conchophthirus acuminatus a very convenient model to address numerous fundamental questions relating to symbiosis and commensalism. The acquisition of food by the ciliate as a result of Dreissena filtration activity is probably the basis of the symbiosis, with additional benefits to C. acuminatus being shelter, provision of oxygen, and dispersal. The number of C. acuminatus in a Dreissena population depends on the mussel's size-frequency distribution as there is a direct correlation between Dreissena size and infection intensity. Lack of a correlation between host density and commensal infection intensity may indicate that D. polymorpha and C. acuminatus have a different environmental optimum. Zebra mussels of a given length in each population may have their own carrying capacity of C. acuminatus infection intensity. Upon reaching this carrying capacity, a symbiont population may have density-dependent feedback mechanisms, which slow its reproduction rate within a host and/or increase its emigration from the mussel to maintain an optimal density within its host. Massive emergence of ciliates into open water may be synchronized with a mass occurrence of recently settled Dreissena juveniles to maximize the infection.

10acommensal10aConchophthirus acuminatus10adispersal mechanisms10ahost specificity10aZebra mussel1 aKaratayev, A., Y.1 aBurlakova, L., E.1 aMolloy, D., P.1 aMastitsky, S., E. uhttp://dx.doi.org/10.2983/0730-8000(2007)26[1153:DPACAW]2.0.CO;201867nas a2200265 4500008004100000245008600041210006900127300001000196490000700206520108000213653002501293653001201318653001401330653003001344653001701374653001301391653002001404653001701424100002201441700002201463700002201485700001901507700002301526856005201549 2003 eng d00aSeasonal Dynamics of Endosymbiotic Ciliates and Nematodes in Dreissena polymorpha0 aSeasonal Dynamics of Endosymbiotic Ciliates and Nematodes in Dre a73-820 v833 a

We report the results of a two-year study in the Svisloch River (Minsk, Belarus) on the dynamics of infection in Dreissena polymorpha by nematodes and three ciliate species Conchophthirus acuminatus, Ophryoglena sp., and Ancistrumina limnica. Although these endosymbionts were present in most of the samples, their prevalence and infection intensity differed significantly. C. acuminatus and A. limnica infection intensities in both years of the study had a maximum in summer and were positively correlated with water temperature. In contrast, Ophryoglena sp. and nematode infection intensities were considerably lower in summer versus winter and were negatively correlated with temperature. In the first long-term study to monitor the size and reproductive rate of C. acuminatus, we found that mean length was negatively correlated with temperature and that temperature was positively correlated with asexual reproduction, with a peak of cell division in April as water temperatures increased.

10aAncistrumina limnica10aBelarus10acommensal10aConchophthirus acuminatus10aEndosymbiont10aNematode10aOphryoglena sp.10aZebra mussel1 aKaratayev, A., Y.1 aMastitsky, S., E.1 aBurlakova, L., E.1 aMolloy, D., P.1 aVezhnovets, G., G. uhttp://dx.doi.org/10.1016/S0022-2011(03)00043-002102nas a2200205 4500008004100000245015700041210006900198300001200267490000700279520142300286653001201709653001401721653001701735653001201752653001701764100002201781700001901803700002201822856005201844 2000 eng d00aSeasonal Dynamics of Conchophthirus acuminatus (Ciliophora, Conchophthiridae) Infection in Dreissena polymorpha and D. bugensis (Bivalvia: Dreissenidae)0 aSeasonal Dynamics of Conchophthirus acuminatus Ciliophora Concho a397-4040 v363 a

Although considerable research has been carried out on Dreissena spp., relatively little is known about the symbiotic organisms living within them. We report a two-year study of the dynamics of infection by the commensal ciliate Conchophthirus acuminatus in D. polymorpha and D. bugensis populations in the Dnieper River in the Ukraine and in four D. polymorpha populations in Belarus. C. acuminatus was present in all samples. The moderate to high infection prevalence and moderate infection intensity that we recorded in D. polymorpha populations were in contrast to the low prevalence and very low intensity of infection observed in D. bugensis. Recording C. acuminatus in D. bugensis represents the first record of any ciliate species from this mussel and the first report of C. acuminatus in a host other than D. polymorpha. Since infection prevalence and intensity strongly correlated with the size of D. polymorpha, the presence of large, infected mussels is likely important to serve as a reservoir for maintaining infection in the overall population. To infect new host mussels, C. acuminatus must disperse into surrounding waters, and we suggest that a period of mass dispersal may be synchronized to occur when new potential hosts, i.e., juvenile mussels, become abundant.

10aBelarus10acommensal10aEndosymbiont10aUkraine10aZebra mussel1 aKaratayev, A., Y.1 aMolloy, D., P.1 aBurlakova, L., E. uhttp://dx.doi.org/10.1016/S0932-4739(00)80045-0