Judith M. Capuzzo

Physiological and biochemical aspects of embryonic and larval development of the winter flounder Pseudopleuronectes americanus

Eggs and larvae of the winter flounder Pseudopleuronectes americanus Walbaum were hatched and raised in the laboratory under controlled conditions. Biochemical composition was measured during development and found to be similar to that of other species: 65 to 80 percent protein, 15 to 30 percent fat, and 0 to 5 percent carbohydrate. Ash content was 7 to 10 percent of dry weight. The chorion comprised more than half of the weight of an egg and the data suggested that it was possibly a source of nutrition to the developing embryo. The sequence of utilization appeared to be carbohydrate and then protein to hatching, lipid, mixed lipid and protein, the predominantly protein until feeding began. Carbohydrate was accumulated at first feeding and depleted when growth began. Protein and lipid were deposited in approximately constant proportions. Respiration rates of eggs were low, 0.002–0.015 μl O2 egg-1 h-1, but rose gradually from fertilization to hatching. Respiration rates of early larvae were from two to eight times that of eggs (0.033–0.131 μl O2 larva-1 h-1). Variation in larval respiration rates indicated a three-fold difference in rate according to level of activity. Eggs excreted ammonia at an increasing rate from fertilization to hatching. Larvae excreted ammonia, primary amines, and other unidentified organic nitrogenous substances. Rates of excretion and proportions of excretory products varied with stage of development. Primary amine excretion was variable and a major component in early stages. Ammonia-N excreted was two to 20 times primary amine N excreted. Unidentified substances were the predominant form of N excretion during early feeding. Ammonia accounted for most of the N excreted in older larvae. Early specific growth rates were 2.1 and 5.5%. Net caloric conversion and net and gross nitrogen efficiencies were low in first feeding larvae compared to adult fishes (32.2, 27.7, and 10.7% respectively).

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.

Changes in digestive enzyme activities during early development of the American lobster Homarus americanus Milne Edwards

Abstract Activities of digestive protease, lipase, and amylase from the foregut and midgut gland were measured during the course of early development in the American lobster Homarus americanus Milne Edwards. Total enzyme activities were very low among embryos sampled 3 days prior to hatching. Protease and amylase activities increased slightly at the time of hatching and again during larval Stage I; lipase activity did not change. Activity of the three enzymes more than doubled among Stage II larvae and although there were slight increases in enzyme activities during Stage III, they were not significant. Protease activity peaked during Stage IV, whereas lipase and amylase activities were greatest among Stage V juveniles. Different patterns were observed when specific enzyme activities (normalized on the basis of protein) are examined. Specific activities of the three enzymes were very low in embryos just prior to hatching and increased slightly during the hatching process. During Stage I, the specific activity of protease doubled, lipase specific activity increased by a factor of 10, and that of amylase increased slightly. Activities of both protease and amylase more than doubled in Stage II larvae; in general, there were no significant differences in specific activities measured in Stages II through V. Lipase specific activity did not change significantly among Stages I through V. The increase in enzyme activities among the hatching stages correlates well with morphological changes observed in the midgut gland (hepatopancreas), specifically in regard to the presence of enzyme-producing B-cells. Changes in enzyme activities among the postmetamorphic Stages IV and V may be related to changes in body form, habitat, or patterns of energy storage and utilization. Lobster larvae normally hatch during early summer but embryonic development can be accelerated in the laboratory by maintenance at high (21°C) rather than ambient temperature. Temperature conditions during embryonic development, however, had no effect on digestive enzyme activities of larvae that were induced to hatch out of season.

Combined toxicity of free chlorine, chloramine and temperature to stage I larvae of the American lobster Homarus americanus

Abstract The differential effects of free chlorine and chloramine on stage I larvae of the American lobster Homarus americanus have been investigated in continuous flow bioassay units. Applied chloramine was more toxic than corresponding concentrations of applied free chlorine to lobster larvae with estimated lc 50 values at 25° of 16.30 mg/l applied free chlorine and 2.02 mg/l applied chloramine. The synergistic effect of temperature on the toxicity of both free chlorine and chloramine has also been demonstrated. Exposure to applied free chlorine at 20° resulted in no significant mortality of test organisms, whereas exposure at 30° resulted in an estimated lc 50 value of 2.50 mg/l. Applied chloramine was considerably more toxic with an estimated lc 50 value at 20° of 4.08 mg/l and at 30° of 0.56 mg/l. The action of each toxicant appeared to be an alteration of standard metabolic activity as revealed by changes in respiration rates during and after exposure to applied free chlorine and chloramine. Initial respiratory stress was detected during exposure to 0.05 mg/l applied chloramine and 5.00 mg/l applied free chlorine. Reductions in respiration rates 48 h after exposure were observed with exposure to all concentrations tested, similar results being obtained following exposure to 0.05 mg/l applied chloramine and 0.10 mg/l applied free chlorine. These results are indicative of the need for information in addition to that obtained in standard bioassays for an adequate assessment of chlorine toxicity. The apparent chlorine demand of the seawater used in this study was determined after removal of particulate and dissolved organics and ammonia. Approximately 18% of the applied level of free chlorine and chloramine was recovered as residuals, measured by amperometric titration; however, no reason for this low recovery has been determined. Until it has been established that undetected chlorine and chloramine in seawater do not result in the production of toxic compounds, both applied and residual levels should be reported in toxicity studies.

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.

Degradation of Artemia lipids under storage

Abstract 1. 1. The total lipid, lipid class and fatty acid composition of Artemia were examined for evidence of enzymatic or oxidative degradation during sample storage. 2. 2. A variety of storage techniques were tested with storage times of 7, 30 or 105 days. 3. 3. At − 20°C, enzymatic degradation resulting in the formation of free fatty acids from phosphatidyl (P.) choline and P. ethanolamine was found to occur in trace amounts after 7 days and significant amounts after 105 days. 4. 4. No evidence of oxidative degradation of fatty acid double bonds was seen. 5. 5. Lipid classes were determined using an Iatroscan (TLC-FID) and a new solvent system for neutral lipid analysis is introduced.

Characterization and site description of Solemya borealis (Bivalvia; Solemyidae), another bivalve-bacteria symbiosis

Solemya borealis Totten was collected from anoxic sediments in Buzzards Bay, Massachusetts in April and July 1989 and examined for the presence of symbiotic, chemoautotrophic bacteria. In addition, sediment cores collected at the same site were analyzed throughout the year, to provide a detailed description of the S. borealis habitat. Here we present structural, enzymatic, biochemical, and stable isotope data which suggests that S. borealis, like the related species Solemya velum Say and Solemya reidi Bernard, contains high concentrations of symbiotic chemoautotrophic bacteria in gill bacteriocytes which play a significant role in nutrition. Transmission electron microscopy revealed the presence of rod-shaped cells, which resemble Gram-negative bacteria, within gill epithelial cells. Ribulose-1,5-bisphosphate carboxylase activity in cell-free extracts of S. borealis gill tissue was comparable with that found in other invertebrate-chemoautotroph symbioses. Very negative δ34S ratios (-32.6 to-15.7‰) suggest the utilization of porewater sulfides as both an energy and a sulfur source for the symbionts. Carbon and nitrogen stable isotope ratios were extremely negative (δ13C=-32 to-34.6‰, δ15N=-9.7 to-8.6‰), similar to those of other bivalve-chemoautotroph symbioses. High concentrations of cis-vaccenic acid, a fatty acid previously found in other invertebrate-chemoautotroph symbioses, were found in all the major lipid classes of the gills of S. borealis. The stable isotope ratios and lipid composition of S. borealis suggest that most of this bivalves nutritional requirements are supplied by bacterial endosymbionts. High levels of taurine in the free amino acid pool of S. borealis suggest the existence of unusual amino acid metabolic pathways which may be the result of endosymbiont activity. The S. borealis specimens were found in relatively shallow water sediments dominated by silts and clays. The sediments contain high concentrations of organic carbon and nitrogen, exhibit limited oxygen penetration, and have high rates of ammonium and sulfide input from the anaerobic microbial community. Sediment C and N stable isotope ratios reflect the input of algal-derived nutrients to the sediments (δ13C=-20.7 to-20.9‰, δ15N=+7.7 to +20.8‰). Sediment δ34S ratios ranged from-18.7 to-25.1‰ demonstrating the presence of sulfur produced by bacterial dissimilatory sulfate reduction processes.

Effects of toxic chemicals in the marine environment: predictions of impacts from laboratory studies☆

Abstract The degree to which toxicity testing can lead to predictions of long-term environmental consequences of contaminant exposure has been widely debated. Laboratory approaches designed to address both chemical concerns of contaminant bioavailability and persistence in addition to biological concerns of sublethal effects on marine organisms would be most useful in providing the linkage between laboratory and field evaluations. Examples of bioenergetic, developmental, and reproductive abnormalities observed with exposure to lipophilic organic contaminants are discussed in reference to consequences at higher levels of biological organization. Alterations in bioenergetics linked with observations of reduced fecundity and viability of larvae, abnormalities in gamete and embryological development, and reduced reproductive effort provide a strong empirical basis for examination of population responses. Such empirical data can be incorporated into population models to assess the effects of energetic, reproductive and developmental aberrations on population success and provide the basis for further examining the predictive value of toxicity testing.

The effects of halogen toxicants on survival, feeding and egg production of the rotifer Brachionus plicatilis

Abstract The toxicity of free chlorine and combined chlorine as chloramine to the rotifer Brachionus plicatilis at three exposure temperatures has been evaluated. Chloramine was more toxic to rotifers than the free halogen form with LC 50 values for 30-min exposures at 20 °C of 0·35 mg l −1 applied chloramine and 1·20 mg l −1 applied free chlorine, 0·02 mg l −1 and 0·18 mg l −1 residual levels, respectively. The synergistic effect of temperature on the toxicity of both halogen forms was also noted. Rotifers surviving exposure to either halogen toxicant had significantly lower filtration rates and egg production rates than control animals. The reduced reproductive rates were not sustained by the second generation of rotifers and it appears that exposure to free chlorine or chloramine does not result in a permanent alteration in the reproductive potential of rotifer populations.