Date of Award

1986

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

The tolerance, bioenergetics, growth, molting frequency and biochemical composition of juvenile blue crabs, Callinectes sapidus, exposed to the water-soluble fraction of South Louisiana crude oil were determined during a 21-d exposure period. Blue crabs were highly tolerant to petroleum hydrocarbons; the LC50 was 3927 ppb on day 21. Rates of energy intake decreased with increasing hydrocarbon concentration. Although energy expenditure rates of crabs exposed to 2504 ppb were not significantly higher than that of control crabs, they were significantly higher than those of crabs exposed to 820 and 1476 ppb. The resulting decrease in scope for growth was thus due to both a decrease in energy intake at higher exposure concentrations and a dose-dependent increase in energy expenditure. Molting was delayed in crabs exposed to 1476 and 2504 ppb. Crab growth was significantly reduced in a dose-dependent manner. The correlation between scope for growth and tissue growth was highly significant, indicating a bioenergetic basis for the decreased growth in crabs exposed to petroleum hydrocarbons. RNA content of crabs exposed to crude oil was significantly reduced on all sampling dates. Protein content of crabs exposed to crude oil was lower than that of control crabs on days 14 and 21. DNA content was not significantly different from that of control crabs, suggesting that the differences in tissue content was due to differences in cell content and not cell number. RNA:DNA and protein:DNA ratios were significantly reduced in crabs exposed to crude oil. The ratios were positively correlated with scope for growth and observed growth. The significant correlations suggest the possibility of their use as indicators of physiological condition. Significant differences in lipid content and concentration were observed. Analysis of five lipid classes indicate that structural lipids were less affected than lipids used for energy storage among crabs exposed to crude oil. The observed changes growth pattern and biochemical composition suggest that the pattern of energy utilization was altered. Among crabs exposed to petroleum hydrocarbons, growth in size took place despite little increase in tissue content. Available energy was used for growth with little being stored in lipid reserves.

Pages

113

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