Lipogenesis in the intact coral Pocillopora capitata and its isolated zooxanthellae: Evidence for a light-driven carbon cycle between symbiont and host

Surface tissue of the reef coral Pocillopora capitata contained approximately 34% lipid on a dry weight basis. Of this, 75% was storage lipid (wax ester and triglyceride) and 25% structural (phospholipid, galactolipid, etc.). Based on chlorophyll a: lipid ratios of intact coral and isolated zooxanthellae, it was determined that over 90% of the storage lipid resided in the host tissue. One half of the structural lipids was found in the host and the other in the symbiotic algae. Gentle fractionation of coral tissue indicated that zooxanthellae possessed less than 14% of the total coral protein. Coral tips and isolated zooxanthellae were incubated with sodium acetate-1-¹⁴C in light and dark to obtain lipogenic rates and proportions of fatty acids and lipid classes synthesized. The rate of lipid synthesis from acetate-1-¹⁴C by intact coral was stimulated three-fold in the light (1200 lux), which indicated that the majority of coral lipogenesis occurred in the zooxanthellae. Intact coral triglycerides contained ca. 68% of the ¹⁴C-activity and wax esters ca. 21%. Zooxanthellae isolated by the Water Pik technique synthesized negligible amounts of wax ester, which implied that wax ester synthesis was a property of the animal tissue. Isolated zooxanthellae and intact coral synthesized identical triglyceride fatty acids from acetate-1-¹⁴C. This study provides evidence for a carbon cycle between host and symbiont whereby the zooxanthellae take up host-derived carbon (probably in the form of acetate), synthesize fatty acids using their photosynthetically derived energy, and return the lipid to the host where it appears as wax ester and triglyceride.     

Effect of light on the total lipid content and storage lipids of the symbiotic sea anemoneAnemonia viridis

In order to examine the effect of light level on the storage lipids of the symbiotic sea anemoneAnemonia virudis (Forskäl), anemones were exposed to three experimental light regimes of 10, 100 and 300 E m^-2s^-1. Anemones were fed once a week. After 30 d there were no significant differences in the total lipid levels between anemones at any of the light intensities. However, after 60 d lipids had increased in proportion to light level in both the animal-tissue and zooxanthellae compartments. The higher levels of total lipid were in part due to increases in storage lipid (wax esters and triglycerides). Wax ester levels increased in the animal tissues but remained constant in the zooxanthellae, whereas triglycerides increased in both compartments. In contrast to fed anemones, starved anemones which were maintained at 300 E m^-2s^-1 for 30 or 60 d did not show a statistically significant change in lipid levels at 60 d, although a slight increase in the lipid level was observed. However, there was a significant increase in the storage lipids, which suggested that the non-storage phospholipids and structural lipids had declined as a result of cellular catabolism. The composition of the wax esters and triglycerides of both fed and starved anemones was analysed and compositional changes were observed at higher light intensities.     

Copper uptake by the sea anemoneAnemonia viridis and the role of zooxanthellae in metal regulation

Anemonia viridis (Forskäl) were collected from south-west Scotland and south-west England in October 1988. When exposed to 0.05 and 0.2mg 1^–1 copper in sea water, anemones did not take up the metal in proportion to external concentrations. Results suggested thatA. viridis regulated copper by expelling symbiotic algae (or zooxanthellae) which were shown to accumulate copper. The use of aposymbiotic (non-zooxanthellate) anemones in similar metal-uptake experiments indicated that other mechanisms may also be involved in metal regulation. Mucus was produced byA. viridis when the anemone was exposed to copper, and it is proposed that mucus may be involved in the regulation process. The implication of this work on the use of coelenterates as biological indicators of environmental metal levels is discussed.     

Cellular and ultrastructural changes in the endoderm of the temperate sea anemone Anemonia viridis as a result of increased temperature

Exposure of the temperate sea anemone Anemonia viridis Forskål to increased seawater temperature (from 16 to 26°C) reduced the lysosomal latency of coelenterate tissues. Lysosomes in the mesenterial filaments of anemones were destabilised by increased temperature, with greater destabilisation in heat-shocked symbiotic anemones than in heat-shocked aposymbiotic anemones in the early stages of the experiment. Lysosomal enzyme activity in zooxanthellae from heat-shocked symbiotic anemones was associated with the algal membranes and the cytoplasm of degenerate algal cells. While the relationship between host coelenterate and symbiotic alga may confer many benefits under normal conditions, comparison of the responses of symbiotic and aposymbiotic anemones to heat shock suggests that there may be disadvantages for symbiotic anemones under stress.     

Acetate incorporation into the lipids of the anemone Anthopleura elegantissima and its associated zooxanthellae

Anthopleura elegantissima containing zooxanthellae, as well as isolated zooxanthellae, incubated with acetate-1-¹⁴C under both light and dark conditions readily incorporate radioactivity into their total lipid pools. In both cases, the specific activity was greatly increased in the light. Dark-incubated anemones and isolated zooxanthellae incorporate activity predominantly into polar lipid; the remainder being present principally in the triglyceride moiety. Light-incubated organisms, however, show a dramatic redistribution of isotope towards greatly increased triglyceride and was ester incorporation, with a concomitant drop in polar lipid. onder light conditions, 70 to 75% of the radioactivity found in the fatty acids of the total zooxanthellae lipid was present in hexadecanoic (16:0) and octadecenoic (18:1) fatty acids. These are also the two major fatty acids by mass. Octadecanoic acid (18:0) is less than 5% by mass. Isotope incorporation patterns suggest that octadecenoic acids arise by elongation of hexadecenoic acids and that this conversion is blocked in the dark. Isotope incorporation patterns for anemones suggest that fatty acids, primarily in the form of saturated or monoenoic fatty acids, are translocated from algal to animal cells. No activity was found in either octadecadienoic (18:2) or octadecatrienoic (18:3) acids. The significance of these data is discussed.     

Lipids of some Caribbean and Red Sea corals: total lipid,wax esters,triglycerides and fatty acids

The Caribbean reef-building corals Porites porites (Pallas) and Montastrea annularis (Ellis and Solander) and the Red Sea corals Pocillopora verrucosa (Ellis and Solander), Stylophora pistillata (Esper) and Goniastrea retiformis (Lamark) were analysed for total lipid, wax ester and triglyceride content, and fatty acid composition. M. annularis contained about 32% of dry weight as total lipid, whereas much lower values of between 11 and 17% were recorded for the other four species. It is concluded that there is greater variation in coral total lipid than hitherto thought. The total lipid contained a substantial proportion of wax ester (22 to 49%) and triglyceride (18 to 37%). The storage lipids (wax esters and triglycerides) accounted for between 6 and 20% of the dry weight and between 46 and 73% of the total lipid. Variation in lipid content between species could not be attributed to geographical location, but the low values for total lipid in Red Sea corals may in part be due to environmental factors as these samples were collected in winter. All corals analysed contained high levels of saturated fatty acids, the most abundant fatty acids being 16:0, 18:0 and 18:1n-9. Marked differences were observed in polyunsaturated fatty acid (PUFA) content between species, with comparatively low levels of 10 and 11% of fatty acids being recorded in M. annularis and G. retiformis, respectively. The values for the other species ranged between 21 and 37%. Fatty acid composition may vary according to the proportions of fatty acids obtained from diet, algal photosynthesis and synthesis by the animal tissues.     

Physiological energetics of the intertidal sea anemone Anthopleura elegantissima

Energy budgets were calculated for individuals of the sea anemone Anthopleura elegantissima (Brandt), collected in 1981 and 1982 from Bodega Harbor, California, USA. Rates of ammonium excretion were measured in high-and low-intertidal, symbiotic and aposymbiotic sea anemones within 24 h of collection. Among symbiotic and aposymbiotic individuals, no differences in excretion rate were found on the basis of intertidal height. However, rates of ammonium excretion in aposymbiotic anemones (2.14 mol NH ₊ ⁴ g^-1 h^-1) were significantly higher than in symbiotic ones (0.288 mol NH ₊ ⁴ g^-1 h^-1). Rates of excretion were used with estimated rates of oxygen uptake to calculate nitrogen quotients (NQ). NQ and RQ values from the literature were used to calculate an oxyenthalpic equivalent [501 kJ (mol O₂)^-1 for R+U], and mass proportions of protein (54%), carbohydrate (44%) and lipid (2%) catabolized during routine metabolism in this species 24 h after feeding. Integrated energy budgets of these experimental anemones were calculated from data on ingestion, absorption and growth, and estimates of translocated energy from the symbiotic algae. Contribution of zooxanthellae to animal respiration based on translocation=90% and RQ=0.97 are 41 and 79% in high-and low-intertidal anemones, respectively. Calculated scope for growth is greater than directly measured growth in both high-and low-intertidal individuals. The deficit, estimated as 30% of assimilated energy in high-intertidal anemones, is attributed to unmeasured costs (specific dynamic effect) or production (mucus). Low-intertidal anemones lost mass during the experiment, implying that the magnitude of the deficit was greater in these anemones than in upper intertidal individuals. Anemones from both shore levels lost zooxanthellae during the experiment, which contributed to energy loss since the contribution of the zooxanthellae is greater in low-intertidal anemones. Scope for growth is preserved in high-intertidal anemones (29% of assimilated energy) because metabolic demands are lower due to aerial exposure, and prey capture rate is higher compared to lowshore anemones. Although possibly underestimated, lower scope for growth in low-shore anemones may result from continuous feeding and digestion processes that are less efficient than those of periodically feeding high-intertidal anemones.     

Metabolic relationships between fatty alcohol and fatty acid in the liver of Squalus acanthias

The high speed supernatant fraction of a homogenate of Squalus acanthias L. liver catalyses the oxidation of oleyl alcohol to oleic acid by an NAD-dependent process. Reduction of fatty acid to fatty alcohol could not be demonstrated. Liver lipids of S. acanthias contain about 60 and 40% of triglycerides and diacyl glyceryl ethers, respectively, with only traces of wax esters. Serum lipids contain 28, 15 and 26% of triglycerides, diacyl glyceryl ethers and wax esters, respectively. Cell-free fractions of S. acanthias liver catalyse the formation of wax esters by an ATP¹-dependent process. The bulk of wax ester synthesis occurs in the high-speed supernatant fraction of liver. The rate of formation of the ester bond in wax esters is comparable to the rate of synthesis of ester bonds in triglycerides, and greatly exceeds the rate of formation of the ether bond in diacyl glyceryl ethers. Results are discussed in terms of possible factors controlling the levels of neutral lipids in S. acanthias.     

Biosynthesis of lipds in zooplankton from Saanich Inlet,British Columbia,Canada

Lipid analyses were carried out on various species of zooplankton captured in Saanich Inlet, British Columbia, Canada, during September, 1972. The amphipod Cyphocaris challengeri had the highest level of lipid, consisting mainly of wax esters. The copepod Calanus pacificus had moderate amounts of lipid, with triglyceride as the major neutral lipid. The euphausiid Thysanoessa raschii contained mainly triglyceride in its moderate levels of neutral lipid, while wax esters and, to a lesser extent, triglycerides were present in the very small levels of neutral lipid in the chaetognath Sagitta elegans. The major fatty alcohols in wax esters of both Cyphocaris challengeri and Calanus pacificus were 20:1 and 22:1, although notable differences were found in the major fatty acids. Biosynthetic studies showed that phospholipids were labelled faster than neutral lipids in all species with both (U-¹⁴C) glucose and (1-¹⁴C) palmitic acid as precursors. Only species containing significant amounts of wax esters in their neutral lipids incorporated substantial amounts of radio-activity from (1-¹⁴C) palmitic acid into wax esters in (i) living animals, (ii) preparations containing fragments of tissue, (iii) cell-free systems. All species incorporated added fatty alcohols into wax esters in preparations containing tissue fragments and in cell-free preparations. Both the fatty acid and fatty alcohols of the wax esters of both Calanus pacificus and S. elegans were labelled from (1-¹⁴C) palmitic acid, consistent with de novo biosynthesis of the esters. (1-¹⁴C) hexadecanol was incorporated into wax esters almost entirely in the fatty alcohol moiety. It is concluded that all species examined formed was esters when presented with preformed fatty alcohols, but only those species that had wax esters as a major component of the neutral lipids were capable of de novo biosynthesis of the lipids.     

Effects of starvation,and light and dark on the energy metabolism of symbiotic and aposymbiotic sea anemones,Anthopleura elegantissima

Rates of oxygen and carbon-dioxide exhange were measured in symbiotic and aposymbiotic specimens of the sea anemone Anthopleura elegantissima while fed and starved under light or dark conditions. Respiratory quotients indicated that fed anemones switched from a carbohydrate to a fat catabolism when starved, with the exception that symbiotic individuals starved in the light showed a pronounced carbohydrate catabolism for over 1 month. The source of the carbohydrate was probably photosynthate translocated by the dinoflagellate Symbiodinium (=Gymnodinium) microadriaticum (Freudenthal) living in the anemones' tissues. The starved symbiotic anemones maintained in the light had lipid levels not significantly different from fed controls and 44 to 61% higher than starved aposymbiotic anemones after 1 month. Thus, the quality and quantity of the metabolic flux from the symbionts to the sea anemone were sufficient to conserve the host's lipid reserves.     

Oxygen as a limiting factor in phototaxis and in intraclonal spacing of the sea anemone Anthopleura elegantissima

Phototaxis in Anthopleura elegantissima, a sea anemone symbiotic with zooxanthellae, was investigated with special reference to oxygen as a possible controlling factor. Under high oxygen concentrations in seawater, movement towards light was not observed for symbiotic anamones as it was under normal oxygen concentrations. Both aposymbiotic and symbiotic anemones demonstrated movement towards high oxygen concentrations in seawater. Oxygen is, therefore, implicated as a controlling factor in phototaxis. Under laboratory conditions, increased intraclonal spacing occurred with low oxygen concentrations in seawater. In the field, individuals in symbiotic clones were spaced significantly closer than in aposymbiotic clones. Since intraclonal spacing is controlled by oxygen in the laboratory, spacing may also be affected in the field by oxygen; symbiotic clones may be spaced closer because they have better oxygen availability than do aposymbiotic clones.     

Diurnal lipid and mucus production in the staghorn coral Acropora acuminata

Net ¹⁴C-accumulation into lipids of Acropora acuminata was rapid and increased with light intensity. Dark ¹⁴C-incorporation was less than 1% noon maximum. Structural lipids were the first radioactively labelled lipid types showing linear ¹⁴C-uptake kinetics. Storage lipids showed non-linear, power-curve kinetics for ¹⁴C-uptake. The rate of ¹⁴C-incorporation into triglycerides and wax esters was maximal during early afternoon and at midday, respectively. Electron microscopic evidence is given for zooxanthellae being primary sites for synthesis of lipids which are exuded from chloroplasts and transferred to animal tissues. Free lipid droplets and crystalline inclusions (wax ester) were common in animal tissues, the inclusions being often associated with mucus-producing cells. The diurnal rate of mucus production was constant. However, ¹⁴C-mucus-lipid production showed a light-dependent diurnal pattern and accounted for 60 to 90% total ¹⁴C of mucus during periods of photosynthetically-saturating light. Here, ¹⁴C was primarily associated with wax esters which were always present in the mucus-lipid. ¹⁴C-triglycerides occur in mucus released only during the day. Lipid and mucus synthesis is discussed in relation to the carbon budget of A. acuminata, in which mucus represented a loss of 40% net C fixation.     

Biosynthesis of wax esters in oceanic crustaceans

Slices from the hepatopancreas of various oceanic curstaceans incorporated radioactivity into wax esters from ¹⁴C glucose and ¹⁴C aspartic acid to a lesser extent and from ¹⁴C palmitic acid to a much greater extent. Radioactivity was incorporated from ¹⁴C palmitic acid into both fatty acid and fatty alcohol moieties of wax esters, the percentage of total radioactivity present in alcohol moieties being greater in deep-living than in shallow-living species. Cell-free preparations from the hepatopancreas but not from muscle, supplemented with ATP and reduced pyridine nucleotides, incorporated radioactivity from 1-¹⁴C palmitoyl Coenzyme A into both fatty alcohol and fatty acid moieties of wax esters. Incorporation into fatty alcohol was NADPH- rather than NADH-specific. Preparations from deep-living species had a greater percentage of total radioactivity in the fatty alcohol moieties of wax esters than preparations from shallow-living species. We conclude that the level of wax esters in a given species is correlated with the rate at which the species biosynthesises these lipids de novo; deep-living species have higher rates of wax ester biosynthesis and higher levels of wax esters than shallow-living species. The results support the thesis that wax esters in oceanic crustaceans are derived largely from the animals' internal biosynthetic activities, presumably in response to particular biochemical and/or physiological requirements, rather than from their diets.     

Effect of feeding regime and irradiance on the photophysiology of the symbiotic sea anemone Aiptasia pulchella

To determine how the animal and algal components of the symbiotic sea anemone Aiptasia pulchella respond to changes in food availability and culture irradiance, sea anemones from a single clone were maintained at four irradiance levels (320, 185, 115, and 45 E m^-2 s^-1) and either starved or fed for 5 wk. Changes in protein biomass of sea anemones maintained under these conditions were not related to the productivity of zooxanthellae, since the protein biomass of fed A. pulchella decreased with increase in irradiance and there was no difference in protein biomass among starved sea anemones at the four irradiance levels. Except for the starved high-light sea anemones, the density of symbiotic zooxanthellae was independent of culture irradiance within both starved and fed. A. pulchella. Starved sea anemones contained over twice the density of zooxanthellae as fed sea anemones. Within both starved and fed individuals, chlorophyll per zooxanthella increased with decreasing culture irradiance while algal size remained constant (in fed sea anemones) at about 8.80 m diameter. Chlorophyll a: c ₂ ratios of zooxanthellae increased with decreasing culture irradiance in zooxanthellae from starved sea anemones but remained constant in zooxanthellae from fed sea anemones. As estimated from mitotic index data, the in situ growth rates of zooxanthellae averaged 0.007 d^-1 and did not vary with irradiance or feeding regime. Photosynthesis-irradiance (P-I) responses of fed A. pulchella indicated an increase in photosynthetic efficiency with decreasing culture irradiance. But there was no consistent pattern in photosynthetic capacity with culture irradiance. Respiration rates of fed sea anemones also did not vary in relation to culture irradiance. The parameter I _k , defined as the irradiance at which light-saturated rates of photosynthesis are first attained, was the only parameter from the P-I curves which increased linearly with increasing culture irradiance. The daily ratio of net photosynthesis to respiration for A. pulchella ranged from 1.6 to 2.8 for sea anemones maintained at the three higher irradiances, but was negative for those maintained at 45 E m^-2 s^-1. Since the final protein biomass was greatest for sea anemones maintained at the lowest irradiance, these results indicate that sea anemone growth cannot be directly related to productivity of zooxanthellae in this symbiotic association.     

The fate of dietary lipids in the Arctic ctenophore Mertensia ovum (Fabricius 1780)

Lipids of the Arctic ctenophore Mertensia ovum, collected from Kongsfjorden (Svalbard) in 2001, were analysed to investigate seasonal variability and fate of dietary lipids. Total lipids, lipid classes and fatty acid and alcohol compositions were determined in animals, which were selected according to age-group and season. Changes in lipids of age-group 0 animals were followed during growth from spring to autumn. Total lipids increased from May to September. Lipids as percentage of dry mass were lowest in August indicating their use for reproduction. Higher values occurred in September, which may be due to lipid storage for overwintering. Wax esters were the major lipid class accounting for about 50% of total lipids in age-group 0 animals from July and August. Phospholipids were the second largest lipid fraction with up to 46% in this age-group. The principal fatty acids of M. ovum from all age-groups were 22:6(n-3), 20:5(n-3) and 16:0. Wax ester fatty alcohols were dominated by 22:1(n-11) and 20:1(n-9) followed by moderate proportions of 16:0. The unique feature of M. ovum lipids was the high amount of free fatty alcohols originating probably from the dietary wax esters. In May, free alcohols exhibited the highest mean proportion with 14.6% in age-group 0 animals. We present the first data describing a detailed free fatty alcohol composition in zooplankton. This composition was very different from the alcohol composition of M. ovum wax esters because of the predominance of the long-chain monounsaturated 22:1(n-11) alcohol accounting for almost 100% of total free alcohols in some samples. The detailed lipid composition clearly reflected feeding of M. ovum on the herbivorous calanoid species, Calanus glacialis and C. finmarchicus, the abundant members of the zooplankton community in Kongsfjorden. Other copepod species or prey items seem to be less important for M. ovum.     

Changes in lipids during the development of Calanus finmarchicus s.l. from Copepodid I to adult

The total lipid and wax ester content as well as the fatty acid and alcohol composition of all copepodid stages and adults of Calanus finmarchicus s.l. were investigated at different locations in the North Sea in 1983 and 1984. Total lipid and the wax ester proportion increased exponentially until Copepodid V. The females were sometimes lower in lipids than the Stage V. The wax ester proportion reached about 90% of total lipids in males and Copepodid V and up to 40% in Copepodid I. The major fatty acids were 16:0, 20:5, and 22:6 and the major fatty alcohols were 16:0, 20:1 and 22:1. At one station the 18:4 acid became one of the dominant acids, because of a Phaeocystis sp. bloom, indicating that the fatty acids of the diet are incorporated mostly unchanged into the lipids of the copepods. The other main fatty acids 20:1 and 22:1 are probably synthesized de novo, serving as precursors for the principal alcohols 20:1 and 22:1. Their levels decreased in the younger stages due to increases in 16:0 alcohol. The fatty alcohol-forming enzyme seems to be specific for saturated and monounsaturated acids, which may be synthesized de novo or derived from diet.     

The composition and biosynthesis of lipids in Thysanoessa raschi from the Clyde Estuary,Scotland

The lipid composition and biosynthesising activity of Thysanoessa raschi collected from the Clyde Estuary, Scotland, in May 1981 were examined. Triacylglycerols were the major lipid class present, although 16.7% of the total lipid were wax esters in which phytol was the dominant fatty alcohol. The thoracic contents (hepatopancreas) of the krill were capable of biosynthesising lipids in vitro from various labelled substrates. Radioactivity from [1-¹⁴C] palmitic acid was incorporated into lipids in the order phospholipids>triacylglycerols>wax esters; the bulk of the radioactivity was present in all cases in the fatty acyl moieties of the lipids. [U-¹⁴C] glucose labelled lipids in the order phospholipids>triacylglycerols>free fatty acids> was esters; in the first two lipids the radioactivity was mainly in the glycerol moieties, whereas in was esters it was solely in the fatty acyl moieties. The extent of labelling of these lipids from [U-¹⁴C] alanine was less than that from [U-¹⁴C] glucose, but the pattern of labelling was generally similar. More than 90% of the radioactivity incorporated into total lipid from ³H₂O was present in free fatty acids from which it was calculated that the hepatopancreas of T. raschi can synthesise 2.5 g of fatty acid per hour at 15°C. This value is approximately three times lower than that previously determined for T. inermis from Balsfjorden, northern Norway. The results are discussed in terms of the sources of the dietary lipids of krill and the role of endogenous biosynthesis in contributing to its lipid reserves.     

Lipogenesis in the arctic euphausiid Thysanoessa inermis

Biosynthesis of lipids by Thysanoessa inermis collected from Balsfjorden, northern Norway, in May 1980, was examined in vitro. The highest concentration of lipid within the krill was in the hepatopancreas, and this organ was the most active in esterifying free fatty acids into wax esters. The hepatopancreas (i.e., thoracic contents) incorporated (¹⁴C) glucose, (¹⁴C) alanine and ³H₂O into wax esters, with the fatty alcohol moieties being labelled more than the fatty acids. (¹⁴C) fatty acid was incorporated preferentially into the fatty acid moieties of wax esters, this incorporation being markedly stimulated by free fatty alcohol. It is concluded that the fatty alcohols of wax esters are preferentially biosynthesized de novo from dietary protein and carbohydrates, whereas the fatty acids derive preferentially from dietary lipid. On the basis of ³H incorporated from ³H₂O, the hepatopancreas in a 50 mg II-group (2 yr old) individual of T. inermis is capable of biosynthesizing de novo, approximately 0.1 mg of lipid (as fatty acids) per day at 5°C.     

Lipid composition and partitioning of deepwater chondrichthyans: inferences of feeding ecology and distribution

The composition of lipids and fatty acids was determined for the livers, muscle, pancreas, kidney and stomach fluids of deepwater chondrichthyan species (including 11 squaliformes, 3 chimaeriformes, 1 hexanchiforme and 3 carcharhiniformes) caught as bycatch from continental waters off south-eastern Australia. The lipid class, fatty acid and fatty alcohol composition differed markedly in each tissue and in each species. The lipid and fatty acid composition of large, lipid-rich (38–70% wet weight, ww) livers demonstrated the multifunctional role of this organ in: lipid distribution, storage and biosynthesis, and buoyancy regulation. In the liver, the importance of certain lipids (including squalene, diacylglyceryl ethers, triacylglycerols and to a lesser extent wax esters) as mediators of buoyancy varied according to lifestyle and habitat. Less variability was observed in the muscle profiles, characterized by low lipid content (<1.0% ww) and high relative levels of polar lipids (>70%). The lipid and fatty acid profiles of the kidney and pancreas showed the highest intraspecific variability, suggesting these organs also have complex roles in lipid storage and metabolism. Overall intra- and interspecific differences in the tissue fatty acid profiles could be related to differences in a number of factors including phylogeny, habitat (depth), buoyancy regulation and diet and presumably also reflect different ecological roles. The lipid and fatty acid profiles are the first published for Rhinochimaera pacifica, Chimaera lignaria and Figaro boardmani and the first to demonstrate interspecific variation in lipid profiles of various tissues of deepwater chondrichthyans. The application of multivariate analysis to lipid class and fatty acid tissue profiles in chondrichthyans inferred dietary differences and metabolic preferences between species and habitats. These results have important implications for the future use of fatty acids as dietary tracers in chondrichthyan research.     

Spatial variability in lipid composition of calanoid copepods from Fram Strait,the Arctic

The calanoid copepods Calanus hyperboreus and C. finmarchicus were investigated in view of their lipid and wax ester content and their fatty acid and alcohol composition. Analyses were performed in females and copepodid stages V and IV from the Fram Strait region between Greenland and Spitsbergen in 1984. This region offers different food conditions like diatom blooms in the North East Water Polynya, food shortage in areas with very close ice cover, high phytoplankton biomass in the marginal ice zone and lower biomass in the open Atlantic water. Lipids contained generally more than 70% wax esters. Highest levels were found in C. hyperboreus with more than 90%. This percentage was not very variable, in spite of large differences in dry weight and lipid content. Copepods with particularly high weight and lipid content were found in the North East Water Polynya. The lightest individuals were found under the pack ice. Lipid proportions per unit dry weight were higher in C. hyperboreus than in C. finmarchicus, whose lowest values were found in the open Atlantic water. Spatial variability in fatty acid composition was much higher than in alcohol composition. The principle alcohols, 20:1 and 22:1, generally accounting for more than 80% of total alcohols. In the North East Water Polynya, the predominant monounsaturated fatty acid was 16:1, while under the ice 20:1 and 22:1 dominated. In the marginal ice zone and in the open water, the 18:4 acid reached percentages up to 30% of total fatty acids. These changes were related to the different food conditions. C. hyperboreus appears to be best adapted to the cold water and unfavourable conditions of polar regions because of its high lipid and wax ester store with long-chain wax esters of high calorific value.