Nonlethal Health Assessment of the Freshwater Mussel Elliptio complanata

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Title: Nonlethal Health Assessment of the Freshwater Mussel Elliptio complanata
Author: Gustafson, Laura L
Advisors: Richard Linnehan, Committee Member
Jay Levine, Committee Co-Chair
Michael Stoskopf, Committee Co-Chair
Tom Kwak, Committee Member
William Showers, Committee Member
Abstract: Freshwater mussels are in decline, with over 70% of North American species categorized as endangered, threatened or of special concern. In an effort to create a nonlethal protocol for health evaluation of freshwater mussels we conducted a series of investigations on wild and captive populations of Elliptio complanata. We tested a method for nonlethal hemolymph collection and found no growth or survival effects in 30 sampled animals relative to 30 controls. We surveyed unionid populations from 19 different stream reaches from a rural region of North Carolina to provide a set of baseline ranges for hemolymph composition in healthy populations. These parameters included hemolymph calcium, magnesium, phosphorus, cell count, glucose, aspartate aminotransferase (AST), ammonia and protein. We tested these parameters in a captive population held under relatively uniform conditions and found most stable over time. Delta 15N declined substantially over time in captivity, likely in response to a large change in environmental _15N signatures. We tested health parameters in three groups of Elliptio complanata after three months under low, moderate or high feed conditions. The treatment groups varied in hemolymph glycogen, magnesium, calcium and phosphorus concentrations and in foot tissue _15N and _13C, providing possible indicators of subtle change in nutritional condition. We also transplanted Elliptio complanata from a stream enriched in _15N-N03 to a relatively depleted stream and evaluated the lag time required for mussel nitrogen isotope signatures to reflect new environmental signatures. We found a slow turnover time but relatively little variability compared to water signatures, suggesting that bivalves may be useful indicators of chronic nutrient loading in rivers and streams. We conclude that, with further research, hemolymph can be a valuable and safe tool for assessment of freshwater mussel population and habitat health.
Date: 2006-02-04
Degree: PhD
Discipline: Comparative Biomedical Sciences

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