Date of Graduation

Summer 2009


Master of Science in Biology



Committee Chair

M. Chris Barnhart


Unionoida, glochidia, parasitism, specificity, captive culture

Subject Categories



Larval parasitism of fish is a critical stage in the lifecycle of freshwater mussels (Unionoida). Most fish species are innately immune to most mussel species, and each mussel is able to utilize only particular host species. The evolutionary origin and mechanisms of host specificity are not well understood. Metamorphosis success (%M = percent of attached glochidia that successfully metamorphose) was analyzed for 25 mussel species and 41 mussel-host species pairs. Mean %M of 14 mussel species with large carnivorous hosts was 79% (range = 57-92%). Among individual fish, %M varied from near zero to 100%, with mean CV = 0.16. Mussels with small insectivorous hosts (n = 21) had lower %M with mean = 40% (range=2-71%) and greater variation among individual fish (CV = 0.49). The %M of six mussel species-host pairs that attach to fins as well as gills was also low with mean %M = 24% (range 19-42%). However, in simultaneous infections %M was higher on fins than gills (p = < 0.001). These results support hypotheses that mussel host infection strategies influence the evolution of host specificity. Differences in %M among individual host fish were tested by inoculating freshwater drum simultaneously with Ellipsaria lineolata and Potamilus alatus. Metamorphosis success of both mussels was strongly correlated among individual hosts (R2 = 86%). The observation that differences in %M among individual fish were not species-specific suggests that individual differences involve a different mechanism than that which determines host-specificity.


© Andrea Kay Crownhart

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