Investigation of freshwater mussel physiology and reproductive biology to inform conservation
Fritts, Andrea Kay
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Filter feeding freshwater mussels (order Unionoida) fulfill an important ecological niche, but a suite of anthropogenic perturbations have made them the most imperiled faunal group in North America. Threats to mussels include habitat degradation, pollution, and alterations to natural flow regimes. The Apalachicola-Chattahoochee-Flint River Basin is a watershed under increasing pressure from human populations and is also home to a diverse assemblage of aquatic organisms including five federally listed mussel species. The federal recovery plan for these species outlines specific research objectives that will better equip scientists and managers with the necessary tools to protect and restore populations of these species. This dissertation has focused on addressing some of these critical data gaps by investigating the ecological relevance of the sodium chloride glochidia viability test, conducting host determination trials for the Purple Bankclimber mussel (Elliptoideus sloatianus), and developing nonlethal methods for assessing the physiological response of mussels to various stress events. Freshwater mussels are characterized by a unique lifecycle in which the glochidia larvae must attach to a vertebrate host to metamorphose into a juvenile mussel. This larval stage is used in toxicity testing to evaluate the effects of contaminants on freshwater mussels and for the derivation of water quality criteria. My results indicated that the viability of glochidia as measured by the sodium chloride test is an ecologically relevant measure of the health of glochidia. The discovery of Gulf Sturgeon (Acipenser oxyrinchus desotoi) as the primary hosts for Purple Bankclimber mussels has supplied important information for the preservation and management of wild mussel populations as well as providing the necessary data to initiate captive propagation. Changes in tissue glycogen and hemolymph chemistry parameters are potential biomarkers for monitoring stress in freshwater mussels. The factors of discharge, size, sex, and species were most commonly found to affect the biological responses in our models and we recommend that future research into the effects of drought and stress should include the use of alanine aminotransferase, aspartate aminotransferase, bicarbonate, and calcium. Combined, these data will allow scientists and managers alike to advance the conservation of these intriguing and ecologically important animals.