Bruce A. Lancaster

Some physiological and biochemical considerations of larval development in the American lobster, Homarus Americanus Milne Edwards☆

The weight-specific respiration rates of fed and starved lobsters and the ammonia excretion rates of fed lobsters increased with each larval stage (I through IV) and decreased with the first postlarval stage (V). The rate of change in metabolic rates was greater than the rate of change of body size of the larval stages, indicating an increased energy demand of the later larval stages. There was no significant difference in the O: N ratio for the first three larval stages but a reduction was observed in stage IV and V lobsters, reflecting an increased dependence on protein catabolism for energy. Protein was the principal biochemical constituent of all lobster stages. Significant decreases in lipid content and increases in ash and chitin content of the last larval (IV) and first postlarval (V) stages were detected.

The effects of petroleum hydrocarbons on lipid metabolism and energetics of larval development and metamorphosis in the american lobster (homarus americanus Milne Edwards)

Abstract In studies with larval stages of the American lobster ( Homarus americanus ) exposed to a sublethal concentration of South Louisiana crude oil, the normal patterns of lipid storage, utilization and synthesis during larval development and metamorphosis were altered with oil exposure. Increased rates of protein catabolism, delayed molting and reduced growth were also evident among oil-exposed lobster larvae and suggest either deficiency or immobilization of lipid reserves. From analyses of lipid class composition of control and oil-exposed lobster larvae, it is evident that oil-exposed larvae have consistently lower levels of triacylglycerols (the major energy store) and higher levels of sterols than control larvae. Decreased ratios of non-essential fatty acids (both saturated and unsaturated) and increased ratios of essential fatty acids were detected in the neutral lipid pools of oil-exposed larvae that suggest both decreased storage of fatty acids in energy reserves and decreased mobilization of essential fatty acids into phospholipid pools. The fatty acid distribution in the phospholipid pools of oil-exposed larvae, however, varied little from control values and reflects a tendency to preserve the integrity of these structural lipids. Increases in sterol levels may be related to decreased mobilization of cholesterol or other sterols and/or transformation of cholesterol into metabolic pathways including the biosynthesis of ecdysterone. Oil-exposed animals contained trace quantities of benzene, thiophene, toluene, alkylcyclohexane and alkylbenzenes, detected with GC-MS analyses. No naphthalene, dimethylnaphthalene, higher molecular weight aromatics or their phenolic derivatives were detected; their absence may be related to either the detection limits of the methodology used or extremely rapid metabolism and turnover of these components. Alterations in lipid metabolism may account for the developmental and energetic abnormalities observed in marine crustaceans. It cannot be ruled out, however, that decreased lipid utilization, synthesis and mobilization may be a defense mechanism against incorporating lipophilic components of petroleum hydrocarbons in metabolic pathways, and that disruption in energetics and development is a consequence of the reduction in energy available for growth and molting.

The relationship between lipid composition and seasonal differences in the distribution of PCBs in Mytilus edulis L.

Abstract The concentrations of individual chlorobiphenyl congeners were measured in the mussel Mytilus edulis transplanted to several stations in Buzzards Bay and Nantucket Sound, MA (USA). Individual stations represented a gradient of chemical contamination and the sampling period extended over a complete annual cycle. Fluctuations in concentrations of some chlorobiphenyl congeners were apparent at all stations during the late spring and early summer with a marked decline occurring during autumn; this pattern was correlated with the seasonal cycle of gametogenesis and spawning activity. Relative redistribution and release of individual chlorobiphenyl congeners associated with spawning is not consistent, suggesting differential partitioning of specific congeners in different tissues or lipid pools. These patterns are consistent with our general view of the bioconcentration of organic contaminants in marine organisms. The major factors controlling the distribution of PCBs in mussels appear to be the relative concentrations of individual contaminants in ambient waters, modified to some extent by differences in partitioning between organisms and water (as indicated by differences in K ow ), and seasonal variations in lipid content.

Hematopoietic neoplasia inMya arenaria: Prevalence and indices of physiological condition

A field survey of hematopoietic neoplasia (Hn) in the soft shell clamMya arenaria (L.) was undertaken using an immunoperoxidase diagnostic technique. Monthly collections ofM. arenaria were made at two sites: Little Buttermilk Bay and New Bedford Harbor, both in Buzzards Bay, Massachusetts, USA, from May 1986 to October 1987. Clams were diagnosed for leukemia and analyzed for soft-tissue dry weight, condition index, and carbon and nitrogen content of the soft tissue. Prevalence of leukemia inM. arenaria exhibited a seasonal fluctuation with a maximum prevalence in fall (September to October) and a minimum prevalence in early summer (March to July). A second maximum peak in late winter (January to March) was observed at one site. Leukemia primarily affected clams that were 3 to 4 yr post-settlement. Lower prevalence levels were observed in both younger and older clams. LeukemicM. arenaria with advanced stages of the disease, were in poorer physiological condition based on dry weight of the soft tissue, condition index, and carbon content of the tissue. Nitrogen metabolism appeared to be unimpaired. Significant differences were observed between the two sites with respect to prevalence of Hn and the physiological condition of clams. Differences in disease prevalence between the two sites may be the result of unknown environmental factors that facilitate initiation of the disease or, that compromise the defense mechanisms of the clams.

Changes in the biochemical composition of a subtropical bivalve, Arca zebra, in response to contaminant gradients in Bermuda

Abstract The biochemical composition of a subtropical bivalve, the turkey-wing mussel Arca zebra , was examined in specimens deployed along two contaminant gradients (Castle Harbour and Hamilton Harbour) in Bermuda. Pooled homogenized samples of the mussel were analysed for protein, ash, total lipid and lipid-class composition. The biochemical composition of A. zebra was similar to that observed in other bivalves that rely on glycogen as their primary energy substratum. Differences were noted in the lipid content and composition in mussels deployed in the two harbours. These differences suggest that Hamilton Harbour has higher food availability than Castle Harbour and so the A. zebra from Hamilton Harbour were in better physiological condition as indicated by higher lipid levels, primarily neutral lipids. The biochemical composition of the mussels provides no evidence that Castle Harbour is impacted by contaminants at a local dumpsite. Mussels deployed at Hamilton Harbour had increasing neutral lipid levels along an increasing contaminant gradient, a pattern observed previously in bivalves impacted by anthropogenic inputs to their environment. These changes may indicate impaired mobilization of free fatty acids from the neutral to polar lipid pools, or possible gonadal resorption following exposure to lipophilic contaminants.

The effects of diet on the growth energetics of postlarval lobsters (Homarus americanus)

Prepared for the Department of Commerce, NOAA Office of Sea Grant under Grant #04-7-158- 44104.

The Effects of Pollutants on Marine Zooplankton at Deep Water Dumpsite 106: Preliminary Findings

The toxicity of duPont’s Grasselli waste to the marine copepods Pseudocalanus sp. and Centropages typicus has been evaluated in 96 hour bioassays. Test organisms were exposed to concentrations of waste ranging from 1 to 1000 ppm and the resulting effects on survival and feeding rates were monitored. Complete mortality of Pseudocalanus was observed at an exposure concentration of 1000 ppm; no mortality was detected among control organisms or those exposed to lesser concentrations. Significant reductions in filtration activity, however, were detected with exposure to 10 and 100 ppm. Significant mortality of Centropages was detected at 100 ppm and exposure to higher concentrations resulted in 100% mortality. Feeding rates of Centropages as measured by both consumption of Artemia nauplii and fecal pellet production rates were significantly lower than control values with exposure to 50 and 100 ppm. The findings of other investigators dealing with the effects of dumped wastes on marine zoo-plankton are discussed.