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;2