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In-vitro Propagation and Fish Assessments to Inform Restoration of Dwarf Wedgemussel (Alasmidonta Heterodon)

The dwarf wedgemussel (Alasmidonta heterodon) is a federally endangered freshwater mussel that once ranged from New Brunswick to North Carolina, but now only exists in isolated populations throughout its diminished range. Laboratory propagation in conjunction with augmentation or reintroduction is considered a critical component of dwarf wedgemussel restoration. My thesis aimed to I) develop in-vitro propagation techniques including methods to minimize microbial contamination for two Alasmidonta species and II) compile and assess critical fish assemblage information at existing dwarf wedgemussel presence and absence locations to inform future restoration activities. For the first objective (Chapter 2) I assessed three methods of contamination mitigation (media change frequency, concentration of the antifungal Amphotericin B, and method of antifungal replenishment). Across all experiments, higher levels of contamination severity had a negative impact on transformation success. In my experiments, dishes that had media changes every other day (vs. those changed daily and every 3 days) had the highest contamination and the lowest glochidia transformation success. Treatments with the lowest (0 µg/mL) concentration of the antifungal, Amphotericin B, and got a low-dose replenishment of Amphotericin B (vs frequent media changes) had the highest transformation success. The fungus was identified as Candida parapsilosis, a common fungus found in aquatic and human environments; future propagation efforts should use mitigation methods that are specific to the fungal contaminant. In the assessment of host fish near dwarf wedgemussel locations (Chapter 3), two fish repeatedly emerged as indicators of dwarf wedgemussel occurrence and abundance: the tessellated darter (Etheostoma olmstedi) and brown trout (Salmo trutta). Tessellated darter was positively related to dwarf wedgemussel which supports the importance of tessellated darter as a host fish in the wild. The negative relationship between dwarf wedgemussel and brown trout may indicate a difference in habitat between the species or brown trout’s predation upon wild hosts. Results from this project will be used in conjunction with habitat and genetic information to inform future restoration plans in the northeast and add to the growing body of literature on in-vitro propagation of freshwater mussels.
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