Changes in dietary lipids were investigated in laboratory feeding experiments simulating herbivorous and coprophagous modes of feeding in the bivalve mollusc Scrobicularia plana (da Costa). The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory experiments while faeces from the crustaceanNeomysis integer (Leach) feeding on Scrippsiella were used as the food in coprophagy experiments. Changes in dietary total fatty acids, sterols and fatty alcohols were characterised by analyses of the food, faeces andanimal tissues using gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). There is a net decrease in the total lipid of the digested material during both herbivory and coprophagy. However, while fatty acids are assimilated, sterols are contributed to the faeces, leading to a decrease in the fatty acid:sterol (FAST) ratio of the digested material. Coprophagy decreases the ratio still further, such that faeces have a FAST ratio of <1 Scrobicularia preferentially assimilates dietary polyunsaturated fatty acids (PUFAs). Reworking of sedimentary material (as in coprophagy) will lead to PUFA-deficient sedimentary fatty acid distributions. Both herbivory and coprophagy lead to relative increases in 'bacterial' odd carbon-number normal and branched fatty acids in the digested material, though not the 'bacterial' marker 18:1 Benthic molluscan feeding, particularly coprophagy, contributes partly to the 'bacterial' fatty acid content of the sediments. Scrobicularia contributes its own sterols to the faeces, especially cholesterol. Such contributions aredependent on the dietary sterols present. With a cholesterol-poor diet (herbivory), A5 4–desmethyl sterols are contributed to the faeces and dietary A8(14) sterols decrease, suggesting a A8(14) U021e2; A5 conversion may occur. With a cholesterol-rich diet (coprophagy), the A5 sterol is taken up from the diet.

This study investigates the effects of benthic feeding upon the lipid composition of material passing through marine food chains. GC and GC-MS were used to determine the changes in dietary fatty acids and sterols in a laboratory food chain involving the dinoflagellate Scrippsiella trochoidea, the pelagic shrimp Neomysis integer and the benthic mollusc Scrobicularia plana. Herbivory of Scrippsiella by both Neomysis and Scrobicularia involves preferential removal of algal polyunsaturated fatty acids (PUFAs) from the food and addition of branched fatty acids (BFAS) to the faeces. Both species contribute 4-desmethyl sterols and remove some algal 4-methyl sterols. Coprophagy of Neomysis faeces by Scrobicularia involves the addition of further BFAs as well as further animal sterols. There is a net removal of fatty acids and a net contribution of sterol in all feeding experiments. Faeces produced coprophagously have the greatest proportion of contributed animal sterol and branched fatty acids, reflecting the feeding by both species. The results suggest that observed fatty acid and sterol distributions in sediment surface material may result primarily from pelagic crustacean feeding, though benthic molluscan feeding in conditions of a settling bloom may give similar distributions. The coprophagy experiment suggests that the lipid distributions of sediment surface material are at least partially due to successive reworking of that material by benthic animals.

A laboratory study simulating herbivorous feeding was carried out with the marine crustacean Neomysis integer (Leach) and the dinoflagellate Scrippsiella trochoidea (Stein). Analyses of the total fatty acids, sterols and fatty alcohols in the food and faecal material, and in the animal tissue, have allowed the detailed changes in the dietary lipids during feeding to be characterised. The results show this feeding leads to a net decrease in total lipid in the material passing through the gut of the animal, particularly due to the bioassimilation of fatty acids. All fatty acid saturation classes are assimilated but the mono-unsaturated and particularly polyunsaturated fatty acids are preferentially assimilated over others. Herbivorous feeding does, however, lead to the quantitative and relative increase in ‘bacterial’-type odd C number branched-chain fatty acids in the faecal material.

Changes in dietary lipids (fatty acids, sterols and fatty alcohols) during herbivory and coprophagy by the annelid worm Hediste (Nereis) diversicolor (O.F. Müller) were modelled in laboratory feeding experiments. The dinoflagellate Scrippsiella trochoidea (Stein) was used as the food in herbivory; faeces from the crustacean Neomysis integer (Leach) after feeding on this same alga, were used as the food in coprophagy.Nereis is extremely efficient in its assimilation of dietary lipids and produces faeces with very low fatty acid:sterol (FAST) ratios in both herbivory and coprophagy. The net decrease in total lipid in both modes of feeding with this species suggests that annelids, where present, are as important as other invertebrate groups in affecting the flux of lipids through marine food chains.

Feeding by marine invertebrates affects dietary lipids as they pass through the gut (Volkmanet al, 1980s; Tanoueet al, 1982; Prahlet al, 1984a, b,1985; Nealet al, 1986; Harvey et ah, 1987,1989). Not only do animals appear to alter the dietary lipids but they also contribute their own lipids to the egested material. Faecal pellets are thus likely to have a lipid composition which has contributions from the ingested food material, the animal itself and the microbial populations residing in the animal's alimentary system.

The fate of 4α,23,24-trimethylcholest-22-en-3β-ol (dinosterol) during passage through the gut of the copepod Calanus helgolandicus and fecal pellet sedimentation has been investigated. An artificial diet of starch granules containing 14C-labelled dinosterol was fed to copepods and compared to 14C-cholest-5-en-3β-ol as a common sterol present in copepod tissues. After feeding, the distribution of radioactivity and the detailed lipid composition of animals and their fecal pellets was determined. Cholest-5-en-3β-ol was readily assimilated by the copepod, with over 62% of the total radioactivity residing in animal tissues. In contrast, 4α,23,24-trimethylcholest-22-en-3β-ol was not assimilated and could be quantitatively recovered in fecal pellets. Additional experiments using copepod fecal pellets containing 14C-labeled dinosterol found no structural alteration during 19 days of simulated sedimentation, with all lipid radioactivity present as dinosterol. Small amounts (6.3%) of radioactivity were present as non-lipid material remaining within fecal pellets. Results from these experiments suggest that dinosterol (and by analogy other ring saturated sterols and stanols) is resistant to crustacean and microbial alterations over the relatively short (20 day) periods typical of sedimentation times for large particles in open ocean areas.

Cellular lipid concentrations of fatty acids, sterols, alcohols, hydrocarbons and 3-keto steroids were determined in laboratory cultures of the marine

This is the first book to deal specifically with this topic. It is essentially a collection of critical reviews outlining the present state of knowledge and indicating future developments. It is designed to meet a wide range of needs, including those of both specialists and students in marine biology, zoology, insect physiology, marine chemistry, comparative biochemistry, oceanography, fisheries biochemistry, and geochemistry.

Stage V and adult females of the marine copepod Calanus helgolandicus were fed in the laboratory on the dinoflagellate Scrippsiella trochoidea at three concentrations calculated to represent pelagic ocean to ‘bloom’ conditions. The identification and quantification of sterols, fatty acids and alcohols present in the algal diet, copepods and their faecal pellets were then carried out using computerized gas chromatography- mass spectrometry (C-GC-MS). The grazing rates of animals were measured and the data then combined with those of lipid distributions in the diet and faecal pellets in order to determine quantitatively the fate of each lipid during its passage through the gut of Calanus. The results showed marked differences in the proportion of the three lipid classes removed, with highest values found for fatty acids and the lowest for sterols. Up to 97% of ingested algal fatty acids were removed by the copepod, with a preference towards the removal of polyunsaturated acids. Algal sterols were also removed by Calanus; the percentage composition and concentration of sterols in faecal pellets differing from the algal diet at all three food levels. Evidence that the removal of lipids from the diet represented assimilation by the copepods was provided by the further finding that during the feeding period (20 hr) all three lipid classes increased in animal tissues. Quantitative measurements of individual sterols revealed that significant amounts of 4-methyl and 4-desmethyl sterols having the 8(14) and 17(20) unsaturation were removed at all dietary levels. In contrast, ring-saturated stanols were not removed and appear to pass through the gut quantitatively.

Numerous studies have shown that only a small percentage of the organic carbon produced by photosynthesis in the upper layers of the oceans reaches the underlying sediments (see review by Angel, 1984). During intense phytoplankton blooms, plant cells could account for most of the organic carbon contributed to sediments in certain shallow inshore areas (Smetacek, 1980). Examination of the sediments from open ocean environments, however, indicates that the main contribution of organic carbon to these is in the form of faecal material released by zooplankton, for example salps (Iseki, 1981) and larger species of copepod (Schrader, 1971; Krause, 1981).

In marine crustaceans the polynuclear aromatic hydrocarbon benzo[a]pyrene undergoes changes mediated by benzo[a]pyrene mono-oxygenase (BPM), a cytochrome P-450 dependent enzyme system requiring molecular oxygen and NADPH as a cofactor: it has now been detected in several species (see O'Haraet al.1982).

Faecal pellet formation within the gut of Stage V and adult females of the copepod Calanus helgolandicus Claus involves (1) cyclical processes of digestion and (2) the contribution of parts of the gut epithelium to the pellets. During an experimental regime in which dim lighting was restricted to day-time and feeding to night-time (17.00 to 09.00 hrs), the copepods responded with cyclical changes in both the quantity of pellets they produced and the fine structure of the contents. During the feeding period, the contents showed changes in the relative amounts of materials originating from disintegrated cells of the digestive epithelium and those derived directly from the ingested food. The vacuolar B-cells of the gut contribute to the content of the pellets and the distal, necrotic N-cells appear to be involved in forming the peritrophic membrane which encloses each pellet. Cells of the gut epithelium which are broken down during feeding are all replaced during the non-feeding period. Other individuals were taken directly from the sea and in these, also, the cells of the gut broke down during feeding and contributed to the faecal pellets. The supply of epithelial cells may limit the duration of the feeding period.

Pelagic zooplankton and fish release faecal material which rapidly sinks through the water column and contributes various amounts and types of organic and other chemical constituents to bottom sediments. The major importance of this process in linking biological events in the water column with inputs to sediments has been well demonstrated in a number of sea areas through the use of field experiments with pumps or traps (Bishopet al.1977; Gagosian, Volkman & Nigrelli, 1983; Honjo, 1978; Knauer, Martin & Bruland, 1979; Prahl, Bennett & Carpenter, 1980; Wakehamet al.1980; Wakeham, Farrington & Volkman, 1983). In general, field studies have shown that the deposition of organic matter of pelagic origin occurs with considerable alterations both quantitative and qualitative (Gagosian, Nigrelli & Volkman, 1983; Prahlet al.1980; Wakeham, 1982). Such studies, however, have not clearly defined how individual biological processes competing in the water column influence the overall composition of organic matter in vertically transported paniculate material.

Dihydrophytol(3,7,11,15-tetramethylhexadecanol) was identified in the nonsaponified lipid fraction of fecal pellets from the copepod Calanus helgolandicus fed in the laboratory on a unialgal diet. Direct deposition in the fecal pellets of certain zooplankton species may explain the presence of dihydrophytol in marine sediments. Microbial reduction of phytol in sediment cores does not account for the origin of this compound in all sedimentary environments.

By means of capillary gas chromatography (GC) and capillary gas chromatography'mass spectrometry (GC/MS), the aliphatic hydrocarbons, fatty acids, fatty alcohols and 3ß-sterols were identified in saponified lipid extracts of the green alga,Dunaliella primolecta, the copepod,Calanus helgolandicus, and faecal pellets released by the animal when fed in the laboratory on the algal diet. Comparison of the lipid data for faecal pellets with those for the plant showed that marked changes to dietary lipids occur during passage through the gut of the copepod: (1) 17:2, 17:1, and 17:0 hydrocarbons are completely eliminated; (2) polyunsaturated fatty acids (e.g. 16:4 and 18:3) are significantly reduced relative to total fatty acids; (3) evidence of the conversion of phytol to dihydrophytol is observed; (4) C28 and C29 sterols with Δ and Δ nuclear unsaturation are selectively removed from the diet relative to Δ components. The Δ sterols are released unchanged as faecal lipids. Cholest-5-enol, absent from the original diet, is also released in the faecal pellets. These observations illuminate the fate of specific dietary lipids inCalanusand the contribution copepod faecal pellets can make to the overall lipid composition of bottom sediment in many marine environments.

A cytochrome P-450-dependent benzo[a]pyrene mono-oxygenase enzyme system (BPM) has been identified and partially characterized in males of the shore crabCarcinus maenas(L.). Apparent Kmvalues obtained at 30 °C using microsomal preparations from the antennary glands of animals collected during summer were in the range 1.61–2.11µM. The cytochrome P-450 content was 0·022 nmol/mg microsomal protein when BPM activity in the same preparation was 0·085 nmol/mg protein/min.

The lipids of four marine coccolithophorids (class Haptophyceae),Emiliania huxleyi, Hymenomonas carterae, Isochrysis galbanaandCrystallolithus hyalinus, were examined by capillary gas chromatography-mass spectrometry. Fatty acids ranged from C14to C22and were predominantly of even chain length. The major acids were polyunsaturated C18acids, 22:6 and either 14:0 or 16:0. C20fatty acids were of low abundance. Significant amounts of octadecapentaenoic acid (18:5), previously thought to be unique to dinoflagellates, were identified in three of the algae. A small amount of a di-unsaturated C36 w-alkenoic acid was identified inE. huxleyi, which is the first report of such a long-chain fatty acid in any alga. Traces of wax esters, which are reportedly uncommon inalgae, were found in three of the species. The sterol distributions were very simple, with two or three compounds accounting for > 99% of the total sterols. In each case, the major component was 24-methylcholesta-5,22E-dien-3β-ol.H. carteraeandC. hyalinusalso contained 24-ethylcholesta-5,22E-dien-3β-ol and significant amounts of cholest-5-en-3β-ol were found inE. huxleyiandI. galbana. An unusual sterol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, was identified inH. carterae. These sterols were mostly non-esterified although small amounts of sterol esters were identified inE. huxleyi. The lipid composition ofE. huxleyiis distinctive in that it contains, in addition to the C36fatty acid, novel C37–C39unsaturated ketones and C31–C38alkenes. Of the other coccolithophorids onlyI. galbanacontained small quantities of one of the C3lalkenes.

The abundance of calanoid copepods in marine plankton and their importance as food for certain fishes has prompted numerous studies of their biology, including several concerned with fecundity (Marshall & Orr, 1952; Mullin & Brooks, 1967; Paffenhöfer, 1970). These studies, however, have all involved animals maintained on various diets in the laboratory: data for egg-production byCalanusunder natural conditions in the sea are still needed.To ensure the survival of the young of many animal species to the stage of independent feeding, biochemical energy in the form of lipid is stored within the egg. During a recent survey ofCalanus helgolandicus(Claus) from the English Channel the level of lipid, mainly in the form of wax esters, in Stage V copepodids was found to be substantially greater than that in female adult stages (Gattenet al.1979). The difference was particularly noticeable during spring periods when egg-laying was in progress. This observation indicates a major role for wax esters during the reproduction ofCalanus.The present study seeks to establish the fate of the lipid reserves in Stage V and female adultCalanuswith particular emphasis on the extent to which the size of such reserves can be used as an index of the fecundity of this copepod.