Charles F. Phleger

Lipids and trophodynamics of Antarctic zooplankton

Abstract Zooplankton were collected by trawl from the Elephant Island region of the Antarctic Peninsula and from East Antarctica near 63–65°S and 139–150°W. Most zooplankton had low percentages of wax esters (0–8%, as percent of total lipid). High triacylglycerol levels were found in the hyperiid amphipod Themisto gaudichaudii (68%, as percent of total lipid), the krill (Euphausiacea) Euphausia tricantha (44–54% triacylglycerol) and Euphausia frigida (27% triacylglycerol) and the scyphomedusan Periphylla periphylla ( 42–48% triacylglycerol). Polyunsaturated fatty acids (PUFA) comprised 23–60% of the total fatty acids, with the omega-3 fatty acids eicosapentaenoic acid [20:5(n-3)] and docosahexaenoic acid [22:6(n-3)] being most abundant. P. periphylla was an exception with 12–19% docosapentaenoic acid [22:5 (n-3)] being the major PUFA. The major euphausiid sterols included cholesterol (75–92%, as percent of total sterols) and desmosterol (6–22%). The major sterols of other zooplankton were more diverse and included trans -dehydrocholesterol, 24-methylenecholesterol, brassicasterol and 24-nordehydrocholesterol. The benthic ascidian, Distaplia cylindrica , had 45% stanols, as percent of total sterols, whereas the pelagic ascidian Salpa thompsonii had only 8–11% stanols. Lipid, fatty acid and sterol data are used to examine trophodynamic interactions and provide an ability to distinguish herbivorous and carnivorous diets and determine survival and reproductive strategies.

Comparison of growth and lipid composition in the green abalone, Haliotis fulgens, provided specific macroalgal diets

Lipid composition of abalone was examined over a one-year interval. A feeding trial was designed to cover a full reproductive cycle in young adult green abalone, Haliotis fulgens, consisting of five diet treatments: the macrophytic algal phaeophyte Egregia menziesii, rhodophyte Chondracanthus canaliculatus, chlorophyte Ulva lobata, a composite of the three algae and a starvation control. The lipid class, fatty acid, sterol and 1-O-alkyl glyceryl ether profiles were determined for foot, hepatopancreas/gonad tissues and larvae. The major fatty acids were 16:0, 18:0, 18:1(n-7)c, 18:1(n-9)c, 20:4(n-6), 20:5(n-3) and 22:5(n-3), as well as 14:0 for abalone fed brown and red algae. 4,8,12-Trimethyltridecanoic acid, derived from algae, was detected for the first time in H. fulgens (hepatopancreas complex, 1.2-13.9%; larvae, 0.5% of total fatty acids). Diacylglyceryl ethers were present in larvae (0.6% of total lipid). The major 1-O-alkyl glycerols were 16:0, 16:1 and 18:0. Additionally, 18:1(n-9) was a major component in hepatopancreas/gonad and larvae. The major sterol was cholesterol (96-100% of total sterols). Highest growth rates were linked to temperature and occurred in abalone fed the phaeophyte E. menziesii (43 microm.day(-1), 56 mg.day(-1) yearly mean), an alga containing the highest levels of C(20) polyunsaturated fatty acids and the highest ratio of 20:4(n-6) to 20:5(n-3). This study provides evidence of the influence of diet and temperature on seasonal changes in abalone lipid profiles, where diet is most strongly related to body mass and temperature to shell length. The allocation of lipids to specific tissues in green abalone clarifies their lipid metabolism. These results provide a basis for improving nutrition of abalone in mariculture through formulation of artificial feeds.

Interannual and between species comparison of the lipids, fatty acids and sterols of Antarctic krill from the US AMLR Elephant Island survey area

Antarctic euphausiids, Euphausia superba, E. tricantha, E. frigida and Thysanoessa macrura were collected near Elephant/ Island / during 1997 and 1998. Total lipid was highest in E. superba small juveniles (16 mg g(-1) wet mass), ranging from 12 to 15 mg in other euphausiids. Polar lipid (56-81% of total lipid) and triacylglycerol (12-38%) were the major lipids with wax esters (6%) only present in E. tricantha. Cholesterol was the major sterol (80-100% of total sterols) with desmosterol second in abundance (1-18%). 1997 T. macrura and E. superba contained a more diverse sterol profile, including 24-nordehydrocholesterol (0.1-1.7%), trans-dehydrocholesterol (1.1-1.5%), brassicasterol (0.5-1.7%), 24-methylenecholesterol (0.1-0.4%) and two stanols (0.1-0.2%). Monounsaturated fatty acids included primarily 18:1(n-9)c (7-21%), 18:1(n-7)c (3-13%) and 16:1(n-7)c (2-7%). The main saturated fatty acids in krill were 16:0 (18-29%), 14:0 (2-15%) and 18:0 (1-13%). Highest eicosapentaenoic acid [EPA, 20:5(n-3)] and docosahexaenoic acid [DHA, 22:6(n-3)] occurred in E. superba (EPA, 15-21%; DHA, 9-14%), and were less abundant in other krill. E. superba is a good source of EPA and DHA for consideration of direct or indirect use as a food item for human consumption. Lower levels of 18:4(n-3) in E. tricantha, E. frigida and T. macrura (0.4-0.7% of total fatty acids) are more consistent with a carnivorous or omnivorous diet as compared with herbivorous E. superba (3.7-9.4%). The polyunsaturated fatty acid (PUFA) 18:5(n-3) and the very-long chain (VLC-PUFA), C(26) and C(28) PUFA, were not present in 1997 samples, but were detected at low levels in most 1998 euphausiids. Interannual differences in these biomarkers suggest greater importance of dinoflagellates or some other phytoplankton group in the Elephant Island area during 1998. The data have enabled between year comparisons of trophodynamic interactions of krill collected in the Elephant Island region, and will be of use to groups using signature lipid methodology.

Lipids of Antarctic Ocean amphipods: food chain interactions and the occurrence of novel biomarkers

Abstract Antarctic hyperiid ( Themisto gaudichaudi , Hyperia macrocephalus , and Primno macropa ) and gammarid amphipods ( Eusirus perdentatus and Orchomene rossi ) were collected near Elephant Island, located in the South Shetland Islands, during January and February 1997 and 1998. Polar lipid (PL) was the major lipid class in all amphipods (58–88% of total lipid), except for T. gaudichaudi in which triacylglycerol (TAG) was dominant (62%). Cholesterol was the major sterol in the gammarid amphipods (89–91% of total sterols), and the hyperiid P. macropa (70%). The hyperiids T. gaudichaudi and H. macrocephalus had a more diverse sterol composition including trans -dehydrocholesterol, desmosterol, 24-nordehydrocholesterol, 24-methylcholest-5,22 E -dien-3β-ol, 24-methylenecholesterol, and stanols (mostly cholestanol). Eicosapentaenoic acid [EPA, 20:5( n −3)] and docosahexaenoic acid [DHA, 22:6( n −3)] were the major polyunsaturated fatty acids (PUFA) in all amphipods. The PUFA octadecapentaenoic acid [18:5( n −3)] was not detected in 1997 samples, but comprised 0.3–1.2% in all 1998 samples. The PUFA 18:4( n −3) comprised 0.2–4.2% in all samples from both years. Very long chain PUFA (VLC-PUFA) (C 24 and C 26 ) were not detected in the one 1997 sample but comprised 0.6–2.8% of total fatty acids in almost all 1998 amphipods. Monounsaturated fatty acids included 18:1( n −9)c, 18:1( n −7)c, and 16:1( n −7)c. Principal saturated fatty acids in all amphipods were 16:0, 14:0, and 18:0. Examination of biomarker lipids has helped clarify trophic interactions for these Antarctic amphipods, and revealed annual differences in their food sources.

Lipids and nutrition of the southern rock lobster, Jasus edwardsii, from hatch to puerulus

We examined the lipid class and fatty-acid composition of the southern rock lobster, Jasus edwardsii, phyllosomas larvae and puerulus stage to improve understanding of their nutrition in relation to aquaculture. Lipid is critical in the nutrition of larval crustaceans, including lobsters. Specimens were from Tasmanian waters, Australia, and North Island, New Zealand, waters. Analyses were by TLC-FID and capillary GC and GC-MS. Phyllosomas larvae and nektonic pueruli were low in storage lipid (triacylglycerol), and phospholipid was the major lipid class. Sterol, mainly cholesterol, was the next most abundant class. The ratio of the essential omega-3 fatty acid eicosapentaenoic acid (EPA) to the omega-6 fatty acid arachidonic acid (AA) was lower in newly hatched phyllosomas (1.2-1.3) than in other phyllosomas (stages III-XI; 2.8-6.7) and pueruli (3.8). Ratios of the omega-3 fatty acid DHA (docosahexaenoic acid) to EPA were also lower in newly hatched phyllosomas (0.5) than in later-stage phyllosomas (1.5-2.1) and pueruli (1.2). We have followed up these compositional data by successfully enriching the live diet (Artemia) of early phyllosomas with AA, EPA and DHA. This dietary manipulation has achieved ratios of these key polyunsaturated fatty acids similar to those of wild phyllosomas. These findings will be of significance to the future of rock-lobster aquaculture.

Lipids of gelatinous antarctic zooplankton: Cnidaria and Ctenophora

Antarctic gelatinous zooplankton, including Cnidaria (Calycopsis borchgrevinki, Diphyes antarctica, Stygiomedusa gigantea, Atolla wyvillei, Dimophyes arctica) and Ctenophora (Beroe cucumis, B. forskalii, Pleurobrachia pileus, Bolinopsis infundibulum) were collected near Elephant Island, South Shetland Islands, during January and February 1997 and 1998. Total lipid was low in all zooplankton (0.1–5 mg g−1 wet mass) and included primarily polar lipids (59–96% of total lipid). Triacylglycerols were 0–26% of total lipids, and wax esters were 0–11% in all species. Cholesterol was the major sterol in all Cnidaria (50–63% of total sterols) whereas in most ctenophores it was lower at 26–45%. These cholesterol levels are consistent with a combined carnivorous and phytoplanktivorous diet in the ctenophores, with the carnivorous diet more dominant in the Cnidaria. Other sterols included primarily trans-dehydrocholesterol, desmosterol, 24-methylcholest-5,22E-dien-3β-ol, 24-nordehydrocholesterol, and 24-methylenecholesterol. Total stanols were 0–6% in all zooplankton. Eicosapentaenoic acid and docosahexaenoic acid were the major polyunsaturated fatty acids (PUFA) in all samples (7–25% of total fatty acids) except for A. wyvillei in which docosapentaenoic acid was 10% of total fatty acids. The PUFA 18∶5n−3 was not detected in 1997 samples, but constituted 0.2–0.8% in most 1998 samples. Monounsaturated fatty acids included primarily 18∶1n−9c, 16∶1n−7c, and 18∶1n−7c. The principal saturated fatty acids in all samples were 16∶0, 18∶0, and 14∶0. These data are the first for many of these zooplankton species and the first sterol data for most species. The use of the signature lipid approach has enabled examination of aspects of trophodynamics not obtainable by conventional techniques.

Lipids and buoyancy in Southern ocean pteropods.

The lipids of Clione limacina, a Southern Ocean pteropod (order Gymnosomata), contain 28% diacylglyceryl ether (DAGE) (as percentage of total lipid) whereas the pteropod Limacina helicina (order Thecosomata) lacks DAGE. The alkyl glyceryl ether diols (1-O-alkyl glycerols, GE) of Clione DAGE are dominated by 16∶0 (60%) and 15∶0 (21%), in contrast with deep-sea shark liver DAGE, which is dominated by 18∶1 GE. The fatty acid profiles of Clione and Limacina are similar (28–32% polyunsaturated, 26–34% monounsaturated) as are the sterols, which include 24-methylenecholesterol, transdehydrocholesterol, cholesterol, and desmosterol. This finding probably reflects the fact that Limacina is the major food source for Clione. Spongiobranchaea australis, another Southern Ocean pteropod (order Gymnosomata), has 0.9–1.7% DAGE, but has less lipid (3.3–4.8 mg/g lipid, wet weight) than Clione (50.8 mg/g lipid, wet weight). We propose a buoyancy role for DAGE in Clione since Limacina has bubbles for flotation which Clione lack; DAGE provides 23% more uplift than triacylglycerol at a concentration of 1.025 g/mL seawater.

Wax esters versus triacylglycerols in myctophid fishes from the Southern Ocean

Five species of myctophid fishes were collected by trawl from the Elephant Island region of the Antarctic Peninsula between 60°30′–62°S and 55°–61°30′W. Two species, Gymnoscopelus braueri and Krefftichthyes anderssoni were lipid-rich (406–456 mg g −1 dry weight whole fish) with wax esters (WE) the major lipid class. In three species, G. opisthopterus, G. nicholsi , and Electrona carlsbergii , triacylglycerols (TAG) were the major lipid. All fish had oily bones, with values up to 471 mg g −1 dry weight in the vertebral centra of K. anderssoni. The principal fatty acids of the TAG-rich myctophids included the monoenes 18:1(n-9) and 20:1. There were lower levels of 16:0 and 18:0 saturated fatty acids. Polyunsaturated fatty acids (PUFA) were present at higher abundance in the TAG-rich E. carlsbergii and G. opisthopterus , with lower levels in G. nicholsi. In comparison, the WE-dominated species contained lower levels of PUFA than in the TAG-rich species. The principal fatty acids of the WE-rich myctophids included the monoenes 18:1(n-9), 16:1(n-7), and 18:1(n-7), with lower levels of the saturated acids 16:0 and 18:0. Fatty alcohols were dominated by 16:0 and 14:0 and the monounsaturated 18:1(n-9) with 16:1(n-7), 18:1(n-7), and 20:1(n-9). Based on the fatty acid profiles, the diet of G. opishtopterus and G. nicholsi , previously thought to be mainly Euphausia superba , is suggested to include copepods and other zooplankton with only a minor krill component, possibly consisting of other species than E. superba.

Composition of oil in fish bones: possible function in neutral buoyancy.

Abstract 1. 1. Three marine fish, Schedophilus medusophagus, Peprilus simillimus and Anoplopoma fimbria , had oil-filled bones, with the skull of P. simillimus and A. fimbria containing 68 and 60 per cent lipid (per cent dry weight) respectively. 2. 2. Triglyceride was the primary component of this lipid, and ranged from 64 to 97 per cent of the bone oil. The major triglyceride fatty acids were 18:1, 16:0 and 16:1. 3. 3. The bones of two fish with fat-filled swimbladders, Coryphaenoides acrolepis and Antimora rostrata , contained only 0·2 per cent lipid (per cent dry weight). The role of bone lipid in neutral buoyancy is discussed.

Marked depletion of polar lipid and non-essential fatty acids following settlement by post-larvae of the spiny lobster Jasus verreauxi.

The development from the non-feeding post-larva (puerulus) to the first instar juvenile of spiny lobsters is highly energetically demanding. These demands may greatly compromise the energy reserves of the lobsters following settlement, leading to reduced growth and survival in the wild, and also in aquaculture. Therefore, the lipid class and fatty acid composition of wild caught pueruli and first instar juveniles of the spiny lobster Jasus verreauxi (H. Milne Edwards, 1851) were analysed by thin layer chromatography-flame ionisation detection and capillary gas chromatography. Pueruli contained substantially more lipid than first instar juveniles (mean difference =3.5 mg, or 41.9%) and most of this difference was due to the presence of greater amounts of polar lipid (mean difference =3.9 mg or 49.2%) in pueruli. First instar juveniles contained significantly more triacylglycerol (mean =0.2 mg), consistent with the polar lipid being converted to a more readily metabolised lipid class in the hepatopancreas. These results indicate that polar lipid is the major energy store during the non-feeding puerulus stage of spiny lobsters from the genus Jasus. Overall, the essential, polyunsaturated linoleic, docosahexaenoic and eicosapentaenoic acids did not show a significant decrease between the two developmental stages, despite the absence of feeding. However, significant reductions in the abundance of both saturated and monounsaturated fatty acids between the two stages were identified (decrease of 811 and 783 microg per individual, respectively). This suggested that selective depletion of non-essential fatty acids may be occurring, with resultant sparing of the essential fatty acids. Supplying diets rich in these depleted fatty acids, and in particular the essential fatty acids, preferably in polar lipid, is likely to result in increased survival and growth of J. verreauxi and other spiny lobsters from first instar juveniles in aquaculture.