Date of Award

2001

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

John W. Fleeger

Abstract

The objective of this dissertation was to determine the partitioning of Cu, Zn and Cd between tissues and exoskeleton of the grass shrimp, Palaemonetes pugio Holthius, and to examine the consequences of this association. The role of the exoskeleton in the potential for depuration of metals through ecdysis was examined first. The portion eliminated with the exuviae varied for each metal; 11% Cu, 18% Zn, and 26% Cd of the total intermolt body burden was associated with exuviae. Some fraction of Cu and Cd in the exoskeleton was likely reabsorbed before molting but excess Zn was likely depurated through excretion. The influence of salinity and source of exposure on metal partitioning among tissue and exoskeleton was then investigated. Grass shrimp were exposed to aqueous metals in 5, 18, and 30‰ seawater or fed metal-enriched algal epiphytes from the stems of Spartina alterniflora . Surface-adsorbed metals ranged from 0--20% of the whole-body burden with the lowest values at 5‰. Metals associated with the exoskeleton matrix ranged from 7--45% with highest values for Zn and Cd. Tissue Cu and Zn burden showed very little variability among the salinity and dietary-exposure treatments likely due to physiological regulation. Finally, the role of partitioning among tissue and exoskeleton in the trophic transfer of metals to the predatory fish Fundulus grandis was examined. F. grandis were fed tissues, total exoskeleton (including the adsorbed metals), or exoskeleton matrix fractions of P. pugio separately for 10 d. Assimilation efficiencies of Cu and Cd associated with the exoskeleton matrix and tissues of P. pugio by F. grandis were relatively low and did not differ. Zn associated with the tissues was highly available, but exoskeleton matrix-bound Zn was essentially unavailable. Surface-adsorbed Cd and Zn were highly available to F. grandis. Surface-adsorbed metals should be considered in future studies because they can be an important vector in food web transfer of metals. However, metals adsorbed to the epicuticle likely do not interact with receptor sites or contribute to toxicity and should be taken into account when determining toxicological endpoints.

ISBN

9780493443515

Pages

105

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