Date of Graduation

2008

Document Type

Dissertation/Thesis

Abstract

Coastal and estuarine organisms face increasing multiple challenges unique to their environment which include natural and anthropogenic stressors that threaten their physiology, fitness, and population persistence. Synthetic pyrethroid and insect growth regulator pesticide use for agriculture, urban and municipal pest control are of increasing concern in coastal areas as other pesticide groups come under strict regulations and that they possess the potential to significantly impact aquatic resources. My research focuses on how current insecticide release in or near coastal marsh environments alter the physiology, limb regeneration and molting ability of a crustacean indicator species, Uca pugnax, in the intertidal and coastal waters of the eastern United States. Little is known about whether low concentrations of pesticide residues in water and sediment enact consequences on crustacean physiological, development and growth processes. A runoff event simulation with permethrin contaminated sediment found that U. pugnax experienced induction of hepatopancreas glutathione S-transferase activity while respiration and hemolymph osmolarity did not vary. This detoxification enzyme holds promise as a generalist biomarker with other lines of evidence for pyrethroid contaminated marine sediments. In addition, Uca pugnax limb regeneration and molting processes following exposure to insect growth regulators or multiple stressors can be used to predict risks to population sustainability of commercially important and increasingly threatened estuarine crustacean populations. Following molt, male crabs displayed decreased body condition due to sexual dimorphic traits, mainly larger body size and disproportionate cheliped. Chronic methoprene exposure at environmental concentrations caused increased male abnormal regenerative limbs and delays in proecdysis. Both male and female crabs displayed increased variability in water-soluble exoskeleton protein possibly affecting exoskeleton quality. Lastly, using a central composite design, male and female crabs were evaluated for non-additive effects of these two pesticide stressors under different salinity regimes on molting processes. Permethrin induced mortality during proecdysis and caused increased growth in male crab regenerative limb growth. In addition, males displayed methoprene and permethrin non-additive effects on total exoskeleton protein content, reduced body mass gain, reduced carapace width gain and overall body condition loss. Females displayed resilience by only experiencing reduced carapace size gain and increased respiration rate, possibly due to increased metabolic and biotransformation of both pesticides. Overall, inputs of insect growth regulators, pyrethroid insecticides or their mixture into coastal wetland environments pose a risk to crustacean physiology, fitness and sensitive growth processes.

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