Date of Graduation

Summer 2009


Master of Science in Biology



Committee Chair

M. Chris Barnhart


Regulations regarding the allowable limits of water pollution are often based on the levels of those pollutants that are toxic to the most sensitive freshwater organisms. Freshwater mussels (Unionoida) are unusually sensitive to certain pollutants and therefore have potential to drive water quality standards. However, data must be based on the normal routes and duration of exposure of each life stage to pollutants. Larval mussels (glochidia) are parasites on the gills or skin of fish. Glochidia of many species are released from the female mussel within aggregates of eggs (conglutinates) that act to attract a host. The host frees the glochidia and becomes infected when attempting to feed on conglutinates. Time spent within conglutinates may far exceed the time spent free in the water. This study compares the toxicity of ammonia and copper to glochidia inside and outside of conglutinates. Two species were investigated, one with cohesive conglutinates (Pleurobema sintoxia) and one with sheathed conglutinates (Ptychobranchus occidentalis). Glochidia of both species remained viable longer within conglutinates than in water, both in the presence and absence of toxicants. P. occidentalis glochidia survived longer than those of P. sintoxia, but the different conglutinate structures of these species appeared to confer similar protection against the toxicants. This information aids in understanding the ecological exposure of glochidia to dissolved aquatic pollutants and in determining protective water quality criteria.


Unionoida, toxicity, water quality, conglutinates, glochidia, ammonia, copper

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