Date of Graduation
Master of Science in Biology
M. Chris Barnhart
Freshwater mussels, in vitro, development, metamorphosis, Unionoid
Captive culture of Unionoid mussels is complicated by the parasitic larval stage, which normally requires a host fish for metamorphosis. Alternatively, some mussel species can metamorphose in vitro, i.e. in an artificial medium in Petri dishes. Most workers have used 5% CO2 atmosphere and bicarbonate to stabilize pH, requiring a specialized incubator. In the present study, in vitro metamorphosis success of Anodonta oregonensis and other species were higher or similar in air than in 1%, or 5% CO2. The nutritional role of the medium was tested by substituting physiological saline without nutrients at varying intervals before metamorphosis was complete. Pyganodon grandis metamorphosed without external nutrition during more than half of the incubation period, suggesting that development, once triggered, can continue largely on internal reserves. Post-metamorphic growth rates of P. grandis from medium, from saline, and from host fish were similar. Previous studies indicate that species which grow substantially during metamorphosis are unsuccessful in vitro. It was hypothesized that higher nutrient use by these species might result in local diffusion-limited depletion of the growth medium, which might be alleviated by circulation. However, initial attempts to metamorphose Leptodea fragilis glochidia in media circulated by a slow rocker system were unsuccessful.