Effects of salinity and temperature on Corophium volutator and C. arenarium (Crustacea: Amphipoda), with particular reference to distribution

The responses of the post-embryonic stages of Corophium volutator (Pallas) and C. arenarium Crawford to the combined effects of salinity and temperature show that gravid females have a wider tolerance than nongravid adult females which in turn are more tolerant than adult males. C. volutator is more tolerant of low salinity (2 to 10) than C. arenarium, but the latter is more tolerant of salinities above 45. The embryos of C. volutator develop normally and hatch at lower salinities and temperatures than those of C. arenarium, in which successful development was recorded at higher temperatures. Females undergoing a pre-copulatory moult failed to lay eggs below salinities of 3 (C. volutator) and 10 (C. arenarium), but in both species the lowest salinity at which all females moulted and laid eggs was 20. The results are discussed in relation to the distribution of both species.     

Saturated and unsaturated hydrocarbons in marine benthic algae

Saturated and olefinic hydrocarbons were determined in 24 species of green, brown and red benthic marine algae from the Cape Cod area (Massachusetts, USA). Among the saturated hydrocarbons, n-pentadecane predominates in the brown and n-heptadecane in the red algae. A C₁₇ alkyleyclopropane has been identified tentatively in Ulvalactuca and Enteromorpha compressa, two species of green algae. Mono-and diolefinic C₁₅ and C₁₇ hydrocarbons are common. The structures of several new C₁₇, C₁₉ and C₂₁ mono-to hexaolefins have been elucidated by gas chromatography, mass spectrometry and ozonolysis. In fruiting Ascophyllum nodosum, the polyunsaturated hydrocarbons carbons occur exclusively in the reproductive structures. The rest of the plant contains n-alkanes from C₁₅ to C₂₁. A link between the reproductive chemistry of benthic and planktonic algae and their olefin content is suggested. An intriguing speculation is based on Paffenhöfer's (1970) observation that the sex ratio of laboratory reared Calanus helgolandicus depends upon the species of algae fed to the nauplii. The percentage of males produced correlates with our analyses of heneicosahexaene in the algal food. Our analyses of the hydrocarbons in benthic marine algae from coastal environments should aid studies of the coastal food web and should enable us to distinguish between hydrocarbon pollutants and the natural hydrocarbon background in inshore waters.Contribution No. 2582 of the Woods Hole Oceanographic Institution; and Contribution No. 227, Systematics-Ecology Program.     

Importance of predation by infaunal polychaetes in controlling the structure of a soft-bottom community in Maine,USA

Field manipulations in a Maine, USA intertidal mud flat showed that Nereis virens adults were an important factor in regulating the abundance of Corophium volutator, an amphipod which comprised 63% of the total number of individuals in the benthic community. Removal of N. virens adults resulted in an increase in C. volutator abundance, while addition of N. virens adults led to a decrease. There was a significant negative correlation between the abundance of N. virens adults and that of C. volutator. C. volutator was also negatively correlated with the density of all the other infaunal species combined. These results suggest that there is at least a 3-level interactive system (N. virens —C. volutator — other infaunal species) within the infauna in Maine; N. virens is a factor in controlling the abundance of C. volutator, and C. volutator may play a role in regulating the densities of other infaunal species. Models of generalized cropping in soft-bottom systems may be too simple if they ignore complex trophic relationships within the infauna.     

Alkanes and alkenes in marine benthic algae

Saturated and olefinic hydrocarbons were determined in additional species of benthic marine algae from the Cape Cod (Massachusetts, USA) area (see: Youngblood et al., 1971). The distribution of homologous and isomeric olefins was studied in plants of different age and in morphologically different parts of the same specimen. With two minor exceptions, only normal alkanes and alkenes are present. The methylene-interrupted C₁₉- and C₂₁-polyolefins are particularly abundant; ¹-heneicosahexaene and the corresponding pentaene are common to all brown algae, while the corresponding ³-isomers occur in green algae. The hydrocarbon concentration, the alkene-to-alkane ratio and the polyolefin content are highest in young plants or in rapidly growing tissues of older plants. This suggests a deeper involvement in cell biochemistry of straight-chain hydrocarbons than previously considered. The biosynthesis of the plant polyolefins remains to be explored; no immediately obvious precursors of the ¹-polyolefins were found among the algal fatty acids. The hydrocarbon composition of these benthic algae differs greatly from that of fossil fuels in its simplicity and predominately unsaturated nature. The separation of the isomers by gas chromatography and their structural elucidation by mass spectrometry, alone and in combination with hydrogenation and ozonolysis, are discussed.Contribution No. 3155 of the Woods Hole Oceanographic Institution.     

Bioturbation effects of the amphipod Corophium volutator on microbial nitrogen transformations in marine sediments

Microcosms containing different densities of Corophium volutator, ranging from 0 to 6000 ind m^-2, were incubated in a flow-through system. Benthic fluxes of CO₂, O₂, NO₃ ^- and NH₄ ⁺ were measured regularly. Thirteen days after setup the microcosms were sacrificed and sediment characteristics, pore water NO₃ ^-, NH₄ ⁺ and exchangeable NH₄ ⁺ concentrations, and potential nitrification activity were measured. The presence of C. volutator increased overall mineralization processes due to burrow construction and irrigation. The amphipods increased the ratio CO₂/O₂ fluxes from 0.73 to 0.86 in microcosms inhabited by 0 and 6000 ind m^-2, respectively. Burrow ventilation removed NH₄ ⁺ from the sediment, which was nitrified in the oxic layer and transported NO₃ ^- to the burrow sediment, where denitrification potential was enhanced. Nitrification and total denitrification rates (denitrification of NO₃ ^- coming from the overlying water and of NO₃ ^- generated within the sediment) were calculated and discussed. Bioturbation by C. volutator increased both nitrification and denitrification, but denitrification was stimulated more than nitrification. Denitrification of NO₃ ^- coming from the overlying water was stimulated 1.2- and 1.7-fold in microcosms containing 3000 and 6000 ind m^-2 relative to control microcosms. The presence of C. volutator (6000 ind m^-2) stimulated nitrogen removal from the system, as dinitrogen, 1.5-fold relative to non-bioturbated microcosms. C. volutator individuals used in our study were collected from Norsminde Fjord, Denmark, in 1990.     

Particle size-selection of two deposit feeders: the amphipod Corophium volutator and the prosobranch Hydrobia ulvae

The feeding biology of the deposit-feeding amphipod Corophium volutator is compared to that of the coexisting, deposit-feeding prosobranch Hydrobia ulvae. Regarding ingestion of particles, both forms show size selection which alone can explain their coexistence. Particle size-selection also explains some qualitative differences in the composition of the food of the two forms; thus, diatoms play a relatively larger role in the diet of H. ulvae than in the diet of c. volutator, whereas bacteria are probably relatively more important for the latter. Results of experiments with feeding of C-14 labelled microorganisms are in accordance with the findings on particle size-distribution of the gut contents, and show that (1) C. volutator can only utilize bacteria adsorbed to particles within the size range 4 to 63 (this is why the presence of clay and silt particles in the sediment are necessary for efficient feeding of this amphipod); (2) C. volutator can utilize bacteria suspended in the water pumped through its burrow for respiration if silt and clay particles are present in the sediment. (3) H. ulvae can utilize large particles, and also browses on surfaces, and some evidence is brought forward that it also utilizes mucus for trapping microorganisms. The coexistence of deposit-feeding animals is discussed. It is concluded that the number of coexisting, closely related species is usually small, and that their resource partitioning is probably mainly based on particle-size selectivity. In the case of unrelated forms (e.g. H. ulvae and C. volutator, a number of behavioural, physiological and morphological differences, and also the widespread ability of deposit feeders to utilize alternative feeding mechanisms may also lead to resource partitioning. Thus, there are often several niche dimensions related to feeding allowing a certain diversity of coexisting deposit feeders.     

Fate of petroleum hydrocarbons taken up from food and water by the blue crab Callinectes sapidus

Radiolabeled paraffinic and aromatic hydrocarbons, including benzopyrene, fluorene, naphthalene, methylnaphthalene, methylcholanthrene, hexadecane, heptadecane and dotriacontane, were taken up from food and water by the blue crab Callinectes sapidus. In 2 days, approximately 10% of the benzopyrene and fluorene were taken up from the water when their concentrations were 2.5 and 30 g/l, respectively. When given food with radiolabeled hydrocarbons, 2 to 10% of the hydrocarbons were assimilated by the carbs, with the remainder excreted. After uptake of hydrocarbon from water or food, a major pathway for the elimination of hydrocarbon and metabolites was through fecal material. All hydrocarbons used in the study were metabolized, with similar rates for both paraffinic and aromatic hydrocarbons. More than 50% of the radioactivity assimilated by the crabs was in the hepatopancreas, suggesting that the hepatopancreas was the site of hydrocarbon metabolism. Twenty-five days aftex exposure to radiolabeled hydrocarbons, radioactivity was found only in the hepatopancreas. The hepatopancreas contained highly polar hydrocarbon metabolites, including dihydroxy-compounds and their conjugates, while blood contained both monohydroxy-and dihydroxy-compounds. No evidence was found of storage of hydrocarbons by any of the crab tissues.     

Accumulation of 14C-1-naphthalene by an oceanic and an estuarine copepod during long-term exposure to low-level concentrations

Accumulation of the bi-cyclic aromatic hydrocarbon ¹⁴C-1-naphthalene in adult female Calanus helgolandicus Claus and adult female Eurytemora affinis Poppe in sea water concentrations of hydrocarbon ranging from 0.2 to 992 g/l was studied during exposure periods of up to 15 days as part of an investigation of the possible effects on marine zooplankton of persistent exposure to low levels of petroleum hydrocarbons. With both species the body levels of radioactivity increased rapidly during the first few days of the exposure period, but after exposure for 7 to 8 days to sea water containing 50 g hydrocarbon/l an equilibrium condition was approached; in some experiments where E. affinis was exposed to 1.0 and 10 g hydrocarbon/l for 15 days there was no further increase in body levels of radioactivity after 7 to 8 days. Using a low concentration of hydrocarbon (1 g/l), the quantity of radioactivity accumulated after 10 days was found to be nearly fifty times greater in the smaller species, E. affinis, than in C. helgolandicus, when expressed in terms of body weight. After they had been exposed to the hydrocarbon for several days the copepods contained a considerable proportion of radioactivity that was no longer identifiable as naphthalene and was presumably present as metabolites. Radioactivity accumulated in the copepods after several days was rapidly lost after they were transferred to uncontaminated sea water: e.g. C. helgolandicus lost nearly 90% of its body level of radioactivity in 24 h. Thereafter the rate of loss was greatly reduced, and 5% of the original body level of radioactivity still remained in the copepods at the end of 11 days. Experiments on the breakdown of naphthalene added at low concentrations to sea water samples containing natural microbial populations indicated degradation rates of 0.1 to 0.2 g/l/24 h in oceanic water, and 2.6 g/l/24 h in inshore water samples. The results are discussed in terms of the possible transfer of hydrocarbon to a higher trophic level in areas subjected to constant low-level inputs of petroleum hydrocarbons.     

Responses of Mytilus edulis on exposure to the water-accommodated fraction of North Sea oil

Individuals of Mytilus edulis L., collected from the Erme estuary (S.W. England) in 1978, were exposed to low concentrations (7 to 68 g l^-1) of the water-accommodated fraction (WAF) of North Sea crude oil. The pattern of accumulation of petroleum hydrocarbons in the body tissues was affected by the presence of algal food cells, the period of exposure, the hydrocarbon concentration in seawater, the type of body tissue and the nature of the hydrocarbon. Many physiological responses (e.g. rates of oxygen consumption, feeding, excretion, and scope for growth), cellular responses (e.g. lysosomal latency and digestive cell size) and biochemical responses (e.g. specific activities of several enzymes) were significantly altered by short-term (4 wk) and/or long-term (5 mo) exposure to WAF. Stress indices such as scope for growth and lysosomal latency were negatively correlated with tissue aromatic hydrocarbons.     

A polyunsaturated hydrocarbon (3, 6, 9, 12, 15, 18-heneicosahexaene) in the marine food web

An olefinic hydrocarbon (all-cis-3,6,9,12,15,18-heneicosahexaene, HEH)_was islated from marine planktonic plants and animals. Its structure was established by ultraviolet, infrared and mass spectrometry in combination with chemical techniques. The olefin occurs in many species of marine planktonic algae and is probably derived from the corresponding docosahexaenoic acid. Rhincalanus nasutus accumulates HEH nonselectively from its algal food together with the triglyceride lipids. Other, related copepods contain little or no HEH even when grown in cultures of algae that provide R. nasutus with that olefin. The presence of HEH in marine vertebrates suggests that, within the animal lipids, hydrocarbons are remarkably stable. This work has practical implications for studies of the marine food web and of marine pollution with persistent chemicals.Contribution No. 2485 of the Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA.     

Secondary metabolites of the leaf surface affected by sulphur fertilisation and perceived by the cabbage root fly

Summary. Surrogate leaves treated with methanolic leaf surface extracts of Brassica napus L. (cv Express) plants that received three different sulphur fertilisation treatments showed even more marked differences by the oviposition choice of Delia radicum L. than the potted plants. This confirms that the oviposition preference of D. radicum is mediated by chemical compounds on the leaf surface and that the quality of host-plants in terms of their nutrition status can be perceived by the female insect.The oviposition data were positively correlated with the content of fractionated surface extracts containing either CIF (cabbage identification factor; 1,2-dehydro-3-thia- 4,10,10b-triaza-cyclopenta[.a.]fluorine-1-carboxylic acid) or glucosinolates. Electrophysiological recordings from the tarsal chemoreceptor sensilla C₅ and D_3,4 showed that receptor neurons react to glucosinolate- and CIF-fractions. We found that the chemosensory activity of specific glucosinolate- and CIF-receptor neurons corresponded with the respective behavioural activity in the oviposition choice assays. The responses of D. radicum to glucosinolates in the electrophysiological recordings studies corresponded to the observed oviposition preference on plants or artificial leaves characterised with an higher amount of glucosinolates on leave surfaces. The presented data suggested that CIF and glucosinolates are involved in host-plant preference of D. radicum and are perceived by tarsal chemoreceptors.     

Relationship between cooling rates,cryoprotectant concentrations and salinities in the cryopreservation of marine microalgae

The viability of the marine microalgae Rhodomonas baltica Karsten, Isochrysis affinis galbana (Strain T-ISO) Parke, Chaetoceros gracilis Schütt, Tetraselmis chuii Butcher, Nannochloropsis gaditana Lubian and Nannochloris atomus Butcher, cryopreservec employing different cooling rates, either with or without the addition of the cryoprotective compounds dimethyl sulfoxide (DMSO) and methanol was studied at two exposure salinities. A viability index, which considered both cell recovery and the growth capacity of microalgae after thawing, was developed. The growth of thawed algae was compared to that obtained for unfrozen algae grown in liquid medium under the same conditions. Viability (V) was calculated according to the equation: V=(C ₀/C _i)x(C ₇/(a·C ₀ ^b ))x100, where C ₀ and C ₇ are, respectively, the initial and final cell densities measured in the cultures after thawing from-196°C, C _i is the maximum initial cell density (complete cell recovery), and a, b are the regression coefficients obtained for C ₇ as a function of C ₀ in the unfrozen controls. R. baltica was the only species that showed an improved viability when salinity was reduced from 36 (average viability 13.7% for 15% DMSO) to 20 (average viability 36.2% for 15% DMSO). The other five species displayed better viability only at the higher salinity at all tested cooling rates and cryoprotectant levels. T. chuii, Nannochloropsis gaditana, and Nannochloris atomus Butcher could be cryopreserved without cryoprotectant. However, their respective viabilities (32.7, 30.8 and 65.8%) at 36 S were progressively improved on addition of 5% DMSO (70.9, 48.2 and 93.5, respectively) and 15% DMSO (91.9, 57.0 and 94.2%, respectively). Similar improvements were found for Nannochloropsis gaditana and Nannochloris atomus when cryopreserved using methanol concentrations of 1% (average viabilities of 46.9 and 91.8, respectively) and 5% (average viablities of 48.7 and 95.3, respectively). Methanol was completely ineffective in cryopreserving the other four species and caused a lethal effect on T. chuii during freezing. C. gracilis could be cryopreserved with 5% DMSO only at 36 S. This resulted in a similar viability (11.7%) to that obtained using 15% DMSO in 20 S (13.7%). Keeping cryoprotectant concentration at 15% DMSO and raising salinity to 36 significantly improved the mean viability of C. gracilis to 21.6%. A low mean viability of 2.1% was obtained for I. galbana when 15% DMSO was used in full-strength seawater (36 S). Within the range of cooling rates tested (0.25 to 16 C° min^-1), cryopreserved microalgae showed higher viabilities at faster rates in the absence of cryoprotectants at both salinities. Generally, the dependence on cooling rate decreased proportionally to the concentration of DMSO or methanol, as demonstrated by the lack of significance for the slope of the regressions. Only C. gracilis appeared to depend on faster cooling rates in the presence of 15% DMSO.     

Impacts of copepods on marine seston,and resulting effects on<Emphasis Type="Italic"> Calanus finmarchicus</Emphasis> RNA:DNA ratios in mesocosm experiments

We investigated the impact of copepods on the seston community in a mesocosm set-up, and assessed how the changes in food quantity, quality and size affected the condition of the grazers, by measuring the RNA:DNA ratios in different developmental stages of Calanus finmarchicus. Manipulated copepod densities did not affect the particulate carbon concentration in the mesocosms. On the other hand, chlorophyll a content increased with higher copepod densities, and increasing densities had a positive effect on seston food quality in the mesocosms, measured as C:N ratios and 3:6 fatty acid ratios. These food quality indicators were significantly correlated to the nutritional status of C. finmarchicus. In contrast to our expectations, these results suggest a lower copepod growth potential on higher quality food. However, in concordance with earlier studies, we found that when copepods were in high densities the large particles (>1000 µm³) decreased and that the smaller particles (<1000 µm³) increased in number. These patterns were closely linked to the condition of C. finmarchicus, which were of better condition (RNA:DNA ratios) with increasing biovolumes of large particles, and, conversely, lower RNA:DNA ratios with increasing biovolumes of smaller particles. Consequentially, the selective grazing by copepods stimulated increased biovolumes of smaller plankton, and this increase was responsible for the increased food quality, in terms of C:N and 3:6 ratios. Thus, we conclude that the decreasing growth potentials of C. finmarchicus were a result of a decrease of favourably sized food particles, induced by copepod grazing.Communicated by O. Kinne, Oldendorf/Luhe     

Effects of kelthane on the estuarine shrimp Crangon tranciscorum

The chlorinated hydrocarbon pesticide Kelthane was assayed for effects on food consumption, molting rate, cannibalism, respiration, mortality and behavior of the estuarine shrimp Crangon franciscorum Stimpson. The test system was a single-pass pulse-flow apparatus employing a modified Mount-Brungs style diluter. Treatment levels were 0, 14, 33 and 81 g l^-1 Kelthane at 16.6°C and 19 S over an exposure period of 317 h. Exposure to Kelthane reduced food consumption, molting rate, cannibalism, and respiration. Behavior also was abnormal in exposed shrimp. They spent more time swimming, were less coordinated and had feeble escape reactions. Kelthane was very toxic to C. franciscorum with LT₅₀ values of 163, 196 and 264 h for shrimp exposed to 81, 33 and 14 g l^-1 respectively. The incipient lethal level of Kelthane is probably below 14 g l^-1.     

Hydrocarbons in the antennal gland secretion of female European beewolves, Philanthus triangulum (Hymenoptera, Crabronidae)

The antennae of female European beewolves (Philanthus triangulum, Hymenoptera: Crabronidae) contain unique gland reservoirs that are inhabited by the symbiotic bacterium ‘Candidatus Streptomyces philanthi’. The reservoir content is secreted into the subterranean brood cells where it serves a dual function: (1) It provides the larvae with spatial information about the orientation of cocoon spinning, and (2) it supplies the larva with the symbiotic bacteria that are needed for the protection of the cocoon against pathogenic microorganisms. We analyzed the hydrocarbon composition of the antennal gland secretion (AGS) by solid phase micro-extraction–gas chromatography–mass spectrometry. We detected 28 substances, the majority of which were saturated and unsaturated hydrocarbons, with minor amounts of some branched alkanes, two ketones, and three unknown substances. There was a strong dimorphism in the chemical composition of the AGS among beewolf females. The two morphs had either (Z)-9-pentacosene (C₂₅-type) or (Z)-9-heptacosene (C₂₇-type) as the main component, and they differed significantly in the relative amounts of most of the other AGS substances. The hydrocarbon composition of the AGS is very similar to that of the postpharyngeal gland of female beewolves, suggesting that the hydrocarbons are universally used for different purposes and transported into the gland from the hemolymph. The putative function of the hydrocarbons in the AGS is discussed.     

The persistence of chronically accumulated hydrocarbons in the hard shell clam Mercenaria mercenaria

Hard shell clams, Mercenaria mercenaria, from the chronically polluted environment of the Providence River, USA, were transferred to a clean laboratory system located in lower Narragansett Bay, Rhode Island. The hydrocarbon contents of these transplanted clams were monitored for 120 days after transfer. After this period only slight depuration had occurred. A 41.9 g g wet weight^-1 average initial hydrocarbon burden decreased to 29.3 g g^-1, a decrease that became statistically significant (P<0.1) only after 120 days. At most, only 30% of the clams' hydrocarbons were lost. These findings indicate that the duration of the exposure period and the chemical nature of the source hydrocarbons are both instrumental in determining the persistence of these compounds in filter-feeding bivalves. Chronically accumulated petroleum hydrocarbons are strongly retained by the organisms and are only very slowly depurated.     

The influence of mercury on the burrowing behaviour ofCorophium volutator

The burrowing behaviour ofCorophium volutator (Pallas) has been recorded in sediments treated with seawater solutions of 0.001, 0.1, 10, and 1000 ppm HgCl₂. Heterotrophic sediment bacteria have also been counted. Non-choice and choice experiments have been conducted. In non-choice experiments no individuals burrowed in the sediment treated with 1000 ppm HgCl₂ solutions. The same numbers of individuals burrowed in the sediments treated with 0.001, 0.1, and 10 ppm HgCl₂ solutions as in the control. Bacterial numbers were lower in the sediments treated with 10 and 1000 ppm HgCl₂ solutions. Hence, a mercury concentration that killed bacteria (10 ppm) did not inhibit burrowing. In choice experiments, individuals avoided all the mercury-treated sediments, particularly that treated with 1000 ppm HgCl₂ solution. Bacterial numbers were only lower than the control in the sediments treated with 10 and 1000 ppm HgCl₂ solutions. Hence, individuals avoided treated sediments (0.001, 0.1 ppm HgCl₂) in which no bacterial mortality had occurred.     

Diurnal gut pigment rhythm and metabolic rate of<Emphasis Type="Italic"> Calanus euxinus</Emphasis> in the Black Sea

The vertical distribution, diel gut pigment content and oxygen consumption of Calanus euxinus were studied in April and September 1995 in the Black Sea. Gut pigment content of C. euxinus females was associated with diel vertical migration of the individuals, and it varied with depth and time. Highest gut pigment content was observed during the nighttime, when females were in the chlorophyll a (chl a) rich surface waters, but significant feeding also occurred in the deep layer. Gut pigment content throughout the water column varied from 0.8 to 22.0 ng pigment female^–1 in April and from 0.2 to 21 ng pigment female^–1 in September 1995. From the diel vertical migration pattern, it was estimated that female C. euxinus spend 7.5 h day^–1 in April and 10.5 h day^–1 in September in the chl a rich surface waters. Daily consumption by female C. euxinus in chl a rich surface waters was estimated by taking into account the feeding duration and gut pigment concentrations. Daily carbon rations of female C. euxinus, derived from herbivorous feeding in the euphotic zone, ranged from 6% to 11% of their body carbon weight in April and from 15% to 35% in September. Oxygen consumption rates of female and copepodite stage V (CV) C. euxinus were measured at different temperatures and at different oxygen concentrations. Oxygen consumption rates at oxygen-saturated concentration ranged from an average of 0.67 g O₂ mg^–1 dry weight (DW) h^–1 at 5°C to 2.1 g O₂ mg^–1 DW h^–1 at 23°C for females, and ranged from 0.48 g O₂ mg^–1 DW h^–1 at 5°C to 1.5 g O₂ mg^–1 DW h^–1 at 23°C for CVs. The rate of oxygen consumption at 16°C varied from 0.62 g O₂ mg^–1 DW h^–1 at 0.65 mg O₂ l^–1 to 1.57 g O₂ mg^–1 DW h^–1 at 4.35 mg O₂ l^–1 for CVs, and from 0.74 g O₂ mg^–1 DW h^–1 at 0.57 mg O₂ l^–1 to 2.24 g O₂ mg^–1 DW h^–1 at 4.37 mg O₂ l^–1 for females. From the oxygen consumption rates, daily requirements for the routine metabolism of females were estimated, and our results indicate that the herbivorous daily ration was sufficient to meet the routine metabolic requirements of female C. euxinus in April and September in the Black Sea.Communicated by O. Kinne, Oldendorf/Luhe     

Ecological role for pteroenone,a novel antifeedant from the conspicuous antarctic pteropod Clione antarctica (Gymnosomata: Gastropoda)

Dense populations of the antarctic pteropod Clione antarctica (Smith) offer a rich source of potential nutrients and energy to planktivorous predators. Nonetheless, antarctic fish do not prey on C. antarctica. Employing flash and high-pressure liquid chromatographic techniques, a linear -hydroxyketone, pteroenone (C₁₄H₂₄O₂) was isolated from whole tissues of C. antarctica. When embedded in alginate food pellets at ecologically relevant concentrations, pteroenone caused significant feeding deterrence in Pagothenia borchgrevinki and Pseudotrematomas bernacchii, two antarctic fish known to feed on planktonic organisms. Concentrations of pteroenone were variable between pteropods (0.056 to 4.5 mg ml^-1 tissue), but even those individuals with the lowest natural concentration contained levels five-fold greater than the lowest effective feeding-deterrent concentration (0.012 mg ml^-1 alginate). Chemical analysis indicated that the primary dietary item of the carnivorous C. antarctica, the shelled pteropod Limacina helicina, does not contain pteroenone. This suggests that C. antarctica does not derive this defensive compound from its diet. This is the first example of a defensive secondary metabolite in a pelagic gastropod.     

Investigation of the sources of aliphatic hydrocarbons in the mussel Mytilus edulis from north sea oil production platforms by Capillary glc and CGCMS†

Aliphatic hydrocarbons isolated from mussels collected over a 20 month period from three North Sea Forties field oil production platforms have been examined by capillary gas chromatography and gas chromatography‐mass spectrometry.

The biological hydrocarbons consist predominantly (300–700 μh g^‐1 lipid) of C₃₁ and C₃₃ n‐alkenes with 2, 3 and 4 double bonds probably derived from a dietary intake of Emiliania huxleyi, a microscopic coccolithophorid alga. In some of the mussels C₁₈, C₂₀ and C₂₂ n‐alkanes are present in unusually high abundance compared to their odd carbon number homologues. Possible reasons for this distribution are discussed.

The concentrations of fossil fuel hydrocarbons (mainly unresolved complex mixtures) in the mussels ranged from 330 to 5,298 μg g^‐1 of lipid. No significant increase in values was detected two months after the start of discharge of treated Forties production water from the Forties D platform.

To determine the pollutant hydrocarbon sources, the sterane and terpane distributions of hydrocarbon fractions isolated from the mussels and from a number of fossil fuels, including Forties crude oil, were examined by mass fragmentography. The steranes in the mussels from the Forties C and D platforms contained higher proportions of regular 14α(H), 17α(H) components than Forties oil in which the steranes were mainly 13ß(H), 17α(H) diasteranes. In addition, the terpane distributions of the mussel fractions differed markedly from that of Forties crude oil, particularly in the relative abundance of diterpanes to triterpanes, which was higher in the mussel fractions than in the oil, and in the absence of 17α(H), 18α(H), 21ß(H)‐18, 30‐bisnorhopane, a known component of Forties crude. Furthermore, the ratio of C₂₉ to C₃₀ triterpanes was greater than unity in the mussels but much less than unity in the Forties oil. These data preclude Forties or other similar North Sea crudes as the major source of pollutant aliphatic hydrocarbons in the mussels. The relative concentrations and distributions of steranes and triterpanes suggest that the most likely source of pollutants is a Middle Eastern based oil derived either from rig activities, or from background pollution in the North Sea. The low concentration of ≥ C₂₇ steranes in the more polluted mussels (e.g. Forties B; UCM > 200 ppm dry wt.) suggests that gas oils used on the platforms may be the major source of petrogenic hydrocarbons in these samples.