Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item COMPARATIVE PHYSIOLOGICAL ECOLOGY OF THE EASTERN OYSTER, CRASSOSTREA VIRGINICA, AND THE ASIAN OYSTER, CRASSOSTREA ARIAKENSIS: AN INVESTIGATION INTO AEROBIC METABOLISM AND HYPOXIC ADAPTATIONS(2012) Lombardi, Sara Ann; Paynter, Kennedy T; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Eastern oyster, Crassostrea virginica, has a remarkable ability to withstand low oxygen conditions. However, the taxonomically and morphologically similar Asian oyster, Crassostrea ariakensis, died earlier than C. virginica during hypoxic exposure in multiple studies. My dissertation research sought to understand the physiological basis for this difference in tolerance. The aerobic metabolic rate of these species was assessed and a theoretical investigation into the importance of correctly standardizing metabolic rate by mass was conducted by using multiple techniques to analyze the respiration data. Crassostrea ariakensis juveniles exhibited higher mass-specific respiration rates than C. virginica , while there was no difference between adults. Further, the approach used to standardize mass vastly affected the results. When adult oysters were exposed to hypoxic water (oxygen concentration below 0.5mgL-1) for 24 hours, C. ariakensis gaped more frequently and wider than C. virginica and gaping was associated with acidification of the ambient water. When gaping was restricted by clamping, the longer an oyster was clamped the more acidic the hemolymph became in both species and a more acidic shift was observed in C. ariakensis. This research also investigated whether hypoxic-induced gaping was a behavioral or physiological response by exposing oysters to hypoxic, hypercapnic, and both hypoxic and hypercapnic environments and assessing metrics of adductor muscle contraction strength and speed. No significant difference was observed in the contraction strength (log10 transformed grams) between species, gas type, or the length of time exposed to the gas treatment. While there was no significant species effect on the speed of contraction (square root transformed seconds until peak contraction strength), oysters within the combined hypoxic and hypercapnic environment contracted more slowly than those in other treatments. When oysters were exposed to gas treatments for eight hours they exhibited the slowest rate of contraction, but there was no significant linear relationship between time exposed and time (square root seconds) to peak contraction strength. This research indicates different biochemical responses to hypoxia between closely related species which may assist in identifying mechanisms responsible for hypoxia tolerance and may contribute to restoration decisions.Item A Comparison of the Biochemistry and Physiology of the Eastern Oyster, Crassostrea virginica, and the Asian Oyster, Crassostrea ariakensis(2007-08-13) Harlan, Nicole Porter; Paynter, Kennedy T; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Chesapeake Bay Foundation, US Environmental Protection Agency, and the Chesapeake Bay Commission, requested research on the introduction of the Asian oyster, Crassostrea ariakensis, to help restore the fishery and ecosystem function of the native Eastern oyster, Crassostrea virginica. In order to augment the role of C. virginica in Chesapeake Bay, C. ariakensis will likely require tolerances to low dissolved oxygen similar to that of the native oyster. This research showed that triploid and diploid C. virginica lived significantly longer than C. ariakensis under anoxic conditions, although the oxygen consumption rates of diploid oysters did not differ between species. Free amino acid pools in the gill tissue of oysters exposed to normoxia or hypoxia were analyzed. Alanine increased in both species during hypoxia, indicating the use of alternative metabolic pathways. Aspartate was consumed by C. virginica during hypoxia, confirming the use of a pathway coupling glucose and aspartate fermentation. Differences in the free amino acid pools of these two species suggest an explanation for the disparity in anaerobic metabolism between C. ariakensis and C. virginica.