Lipids of freshwater dolphinSotalia fluviatilis: Comparison of odontocete bioacoustic lipids and habitat

The melon and jaw lipids of the freshwater dolphinSotalia fluviatilis are composed mainly of isovaleroyl wax esters and diisovaleroyl triglycerides. The blubber fat contains only a trace of wax ester and is mostly tri- (long chain) and monoisovaleroyl triglycerides. Detailed gas liquid chromatographic analyses of the intact wax esters and triglycerides and of the derived fatty acids and fatty alcohols indicate common compositional patterns in the wax esters and triglycerides of the respective head lipids. Both odd and even long chain (C₁₂−C₁₆) iso-structures are prominent in the melon and jaw lipids, but only higher odd chain length iso-acids are major components in the blubber.Sotalia fluviatilis (family Delphinidae) andInia geoffrensis (family Platanistidae) share the same freshwater habitat in the upper Amazon River, and both utilize echolocation to navigate and to find food. Comparison of their respective bioacoustical lipid compositions shows distinctive types of head fats,Sotalia being rich in iso-5∶0 andIndia lacking iso-5∶0. This indicates that isovaleric acid per se has no obligatory role in dolphin echolocation.     

Wax esters and triglycerides as storage substances in seeds of Buxus sempervirens

The seeds of the evergreen Buxus‐tree, Buxus sempervirens, contain a yellowish oil which represents up to 42% of the dry weight. The oil consists, in comparison to the lipids of jojoba fruits (Simmondsia chinensis), of only 3.6% wax esters. 95% of the oil consist of triglycerides, the typical storage substances of oil fruits. Phospholipids occur with 0.4% and glycolipids with 0.13%. The fatty acid patterns of these lipids correspond to the typical fatty acid compositions of the respective lipid classes. In the wax esters monoenoic fatty acids and saturated fatty acids with 16 and 18 carbon atoms prevail. The glycolipid and phospholipid fractions are characterized by a high portion of dienoic and monoenoic as well as saturated fatty acids having 16 and 18 carbon acids.     

Composition of wax esters,triglycerides and diacyl glyceryl ethers in the jaw and blubber fats of the Amazon River dolphin (Inia geoffrensis)

The lower jaw fat of the Amazon River dolphinInia geoffrensis contains 52.8% wax ester, 44.7% triglyceride and 2.5% diacyl glyceryl ether, while its dorsal blubber fat is >98% triglyceride. Examination of the intact lipids, the derived fatty acids and the derived fatty alcohols by gas chromatography reveals that the blubber triglycerides show characteristics of freshwater fish fats, but the jaw fat lipids have several distinctive features. Jaw fat wax esters, triglycerides and diacyl glyceryl ethers are all rich in C₁₀, C₁₂ and C₁₄ fatty acids and contain no polyunsaturated acids. The fatty alcohols in the wax esters are over 90% saturated. The major carbon numbers in the jaw fat triglycerides (C₃₈–C₄₆) are considerably lower than those of the blubber triglycerides (C₄₈–C₅₄). The possible adaptation of the jaw lipids for use in the underwater echolocation process of this dolphin is discussed.     

Trans-6-hexadecenoic acid and the corresponding alcohol in lipids in the sea anemoneMetridium dianthus

Trans-6-hexadecenoic acid was found in polar lipids, triglycerides, was esters and diacylglyceryl ethers of the sea anemoneMetridium dianthus from Passamaquoddy Bay. The corresponding alcomaquoddy Bay. The corresponding alcohol also apparently occurs in the wax esters of this species. The long-chain (C₂₀, C₂₂) monoethylenic alcohols reported for other species of sea anemones from neighboring waters were absent and the major alcohol and glyceryl ether chain both had 16∶0 structures. The isomers of C₁₈ and C₂₀ monoethylenic fatty acids in polar lipids and triglycerides were unusual in their high proportion of theω ₇ isomer. These two lipids also contained higher proportion of the polyunsaturated fatty acids than the others.     

Plasma transport forms of ingested fatty alcohols in the rat

Previous studies have shown that ingested fatty alcohols are absorbed as fatty acids and fatty acid esters, particularly triglycerides. The present study was carried out to determine whether fatty alcohols are also transported as 0-alkyl glyceryl ethers, alk-1-enyl glyceryl ethers, and as wax esters. Oxidation of fatty alcohols to other lipids was assessed by using a mixture of [1-³H] hexadecanol and [1-¹⁴C] hexadecanol of predetermined ratio. The results indicate that the absorption of fatty alcohol, and of its transport forms, parallels the absorption of labeled fatty acids. Six to 25% of plasma radioactivity was present as 1-0-alkyl diacylglyceryl ethers with a smaller proportion of ether lipids in the phospholipid fraction. In addition, 4–13% of the ingested hexadecanol appeared in the plasma as a material having the chromatographic properties of wax ester. Fatty alcohols were not detected in the plasma as alk-1-enyl lipids.     

Chemie der Fischlipide

Chemistry of Fish Lipids The muscle (‘meat’) of freshwater fishes and marine fishes contains 1–25% lipids which are predominantly triglycerides; phospholipids are generally present in rather small proportions. The lipids in the muscle of typical freshwater fishes contain considerable proportions of oleic and linoleic acids, whereas the lipids of most marine fishes contain relatively large amounts of highly unsaturated fatty acids having 20 and 22 carbon atoms. The fatty acid patterns of lipids in the muscle of freshwater predatory fishes resembles to a greater extent that of marine fishes than herbivorous freshwater fishes. In the meat of sharks, alkyldiacylglycerols occur in addition to small amounts of alk-1-enyldiacylglycerols (neutral plasmalogens). In the muscle lipids of marine fishes from depths of more than 1000 m, wax esters predominate. As a rule, the liver of marine fishes, especially of sharks, is rich in alkoxylipids, wax esters, steryl esters, vitamin A esters and hydrocarbons.     

Fatty alcohols in capelin,herring and mackerel oils and muscle lipids: II. A comparison of fatty acids from wax esters with those of triglycerides

The fatty acids recovered from the triglycerides and wax esters of common northwest Atlantic copepods are compared with the fatty acids of wax esters recovered intact from certain fish skin and body lipid, and from commercial fish oils. The fish species, herring, capelin and mackerel, all feed on copepods, and many resemblances of the copepod lipid fatty acids to those of a previous analysis of similar copepods suggest that the basic dietary fat input for these fish may be quite constant. The two copepod fatty acid analyses differed quantitatively in triglyceride 20∶1 and 22∶1 and also in 20∶5ω3 and 22∶6ω3, confirming the primary role of the wax esters in copepods. Selectivity factors are discussed in comparing the copepod wax ester fatty acids with the fatty acids of the wax esters recovered intact from the fish lipids and oils. The basic role of copepods in supplying all types of fatty acids to fish depot fats is considered to be strongly supported by these findings.     

Fatty Acid Specificity of Candida cylindracea Lipase

Candida cylindracea lipase (SIGMA) was tested against triglycerides (TG) and wax esters (WE) of marine origin as substrates. Under the same conditions, wax esters were hydrolysed at a lower rate than the triglycerides. The C₁₄ to C₁₈ saturated and monounsaturated fatty acids were preferentially hydrolysed whereas the longer chain monoenes (20:1 and 22:1) and particularly the polyunsaturated fatty acids (18:4,20:5 and 22:6) were resistant to the hydrolysis in triglycerides as well as in wax esters. No specificity was demonstrated for the fatty alcohols in the wax esters.     

Wax esters in fish: Turnover of oleic acid in wax esters and triglycerides of gouramis

Methyl U-¹⁴C oleate was fed to mature male and female gouramis (Trichogaster cosby) and the radioactivity in lipids measured over a period of four months. Initial incorporations were 70–80% and more than half of that was still in the lipids at the end of the experiment. Very little conversion of the 18∶1 chain had occurred. Main storage of the labeled 18∶1 chain was in the wax esters of the roe and in the triglycerides of the body. In the wax esters, 18∶1 occurred in both the alcohol and acid moieties. Initially the females had less radioactivity in the triglycerides than in the wax esters but at the end of the experiment this was reversed. An appreciable amount of 18∶1 had been transferred from roe to body lipids. The biological half life of 18∶1 in gouramis is estimated to be about four months. This time is equal for males and females although translocation from roe to body and transformation of wax ester to triglyceride take place in the female, whereas wax esters do not play any role in the lipid metabolism of the male.     

Lipid changes during life cycle of marine copepod,Euchaeta japonica marukawa

All stages from egg to adult of the North Pacific copepod,Euchaeta japonica contained wax esters in their lipid stores, while triglycerides were important only in the eggs, early naupliar stages, and adults. The large lipid reserves of the eggs were wax esters and triglycerides (58% and 19% of the lipid, respectively), both of which were used rapidly during the early stages of development. Wax esters continued to decrease after triglycerides had been utilized completely for energy. The slow metabolism of lipid during starvation indicated that lipid stores in adult females may be conserved for egg production. The dominant alcohols of the wax esters of all stages were tetradecanol (24–42% of the total) and hexadecanol (25–65%). Only minor amounts of polyunsaturated alcohols were observed. There was, however, a high proportion of polyunsaturation in the wax ester fatty acids, even though octadecenoic was generally predominant (16–46% of the total wax ester fatty acids). The polyunsaturation of the wax esters fatty acids and the presence of 21∶6 hydrocarbon suggest phytoplankton in the diet of adults and in the younger stages. Cholesterol was the main sterol, but there were minor amounts of desmosterol (1–12% of the total sterols) present. The latter sterol has not been found previously in copepods, although reported from Cirripedia and Decapoda.     

Liver lipids and fatty acids of the sting ray Dasyatis bleekeri (Blyth)

The sting ray, Dasyatis bleekeri (Blyth), has been studied for lipids and fatty acids of its liver. The neutral lipids identified were hydrocarbons, wax esters, steryl esters, 1-O-alkyl-2,3-diacylglycerols, triacylglycerols, and sterols. Neutral lipids were predominant (91.8%), major components being triacylglycerols (92.7%). Polyenoic fatty acids of n-3 series, viz. eicosapentaenoic acid and docosahexaenoic acid, were high in the phospholipid and neutral lipid fractions. Cholesterol was the major component (67.9%) in the steryl ester fraction. Glyceryl ethers, with chainlengths up to 30 carbons, were recorded with unsaturated, anteiso, iso, and normal chains. In wax ester alcohols, up to 32-carbon chains were recorded. Hydrocarbons were up to 36-carbon chains with anteiso, iso, and normal chains. Among branched chain hydrocarbons, pristane was the major component (6.7%) and squalene was present at the level of 3.5%. Chimyl and batyl alcohol backbones were the major components found in 1-O-alkyl-diacylglycerols.     

Wax ester biosynthesis in the liver of myctophid fishes

The biosynthetic properties of wax esters in the liver were compared between two types of myctophid fishes having different body lipid composition, i.e., three triglyceriderich species (Lampanyctus jordani, Diaphus theta, and Symbolophorus californiensis) and three was ester-rich species (L. regalis, Stenobracius nannochir, and Stenobracius leucopsarus). n-Heptadecanol (17∶0-ALC) and/or 10-cis-heptadecenoic acid (17∶1-ACID) was incubated with liver homogenate of the six myctophid fishes and with co-factors such as NADPH and ATP for 2 to 5 h. Considerable amounts of wax esters with odd-numbered fatty acids and/or alcohols were produced in the liver homogenate of the was ester-rich species. Stenobracius nannochir and L. regalis, which exclusively contained wax esters as neutral lipids, showed the highest activity of wax ester synthesis, followed by S. leucopsarus, which contained triglyceride as the minor constituent. Only trace amounts at most of odd-numbered fatty acids and alcohols were incorporated into the wax esters after incubation with the liver homogenates of the triglyceride-rich fishes. Active interchange between the fatty acids and the alcohols occurred during wax ester biosynthesis in the wax ester-rich fishes. The chain elongation and shortening of acyl moieties were also observed during incubation. These results suggested that the deposition of lipids in myctophid fishes is mainly due to their biosynthetic activities.     

Occurrence of wax esters and 1-O-alkyl-2,3-diacylglycerols in goat epididymal sperm plasma membrane

Two unusual lipid classes were detected by thin-layer chromatography in the neutral lipids derived from goat cauda-epididymal sperm plasma membrane. The lipids were identified as wax esters and 1-O-alkyl-2,3-diacylglycerols based on chromatographic properties, identity of their hydrolysis products, and infrared/¹H nuclear magnetic resonance spectral evidence. The membrane containedca. 3 and 5 μg/mg protein of wax esters and alkyldiacylglycerols, respectively. The relative proportions of wax esters and alkyldiacylglycerols in the total neutral lipids were 1.5% and 2.4%, respectively. The lipids contained fatty acids with chain lengths of C₁₄ to C₂₂. The major fatty acids of the wax esters were 14∶0, 16∶0, 16∶1ω7, 18∶0 and 18∶1ω9. The fatty acids in alkyldiacylglycerol were 16∶0, 18∶0, 22∶5ω3 and 22∶6ω3. Alkyldiacylglycerol was particularly rich in docosahexaenoic acid 22∶6ω3) representing 30% of the total fatty acids. The alcohols of wax ester were all saturated with C₂₀–C₂₉ carbon chains. The deacylated products derived from alkyldiacylglycerols were identified as hexadecyl, octadecyl and octadec-9′-enyl glycerol ethers.     

Lipid composition ofNeurospora crassa

The lipids ofNeurospora crassa, isolated in pure form from freeze-dried mycelium, were found to contain squalene, sterol esters, triglycerides, free fatty acids, geranylgeraniol, free sterols, carotenoids, cardiolipin, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl serine, and phosphatidic acid. The above compounds were isolated in pure form by column and thin layer chromatography and were characterized by infrared spectroscopy and chromatographic mobilities. Fatty acid moieties were characterized by gas liquid chromatographic retention times of their methyl esters relative to those of authentic standards. The fatty acid composition of the triglycerides was found to be similar to that of phosphatidic acid, cardiolipin, and lecithin.     

The fatty acids of wax esters and sterol esters from vernix caseosa and from human skin surface lipid

Separation of sterol esters from wax esters in the lipids of vernix caseosa and adult human skin surface was accomplished by column chromatography on MgO. The fatty acids of the sterol esters and wax esters of both samples were separated into saturates and monoenes, and examined in detail by gas liquid chromatography (GLC). The saturated fatty acids of the wax esters of vernix caseosa and of adult human skin surface were remarkably similar. They ranged in chain length from at least C₁₁ to C₃₀, six skeletal types being present: straight even, straight odd, iso, anteiso, other monomethyl branched and dimethyl branched. A large number of patterns of monoenes were observed, each pattern consisting of desaturation of a specific chain at Δ6 or Δ9 plus its extension or degradation products. The mole per cent of the total Δ6 and Δ9 patterns of wax ester fatty acid monoenes of vernix caseosa were 87% and 12%, respectively, and 98% and 1%, respectively, for adult human skin surface lipid. The sterol ester fatty acids of vernix caseosa were much different from those of adult human skin surface: vernix caseosa saturates were largely branched and of lengths greater than C₁₈, whereas the saturates of adult human surface lipid resembled the wax ester fatty acids. Of the vernix caseosa monoene patterns, the mole per cent was 30% Δ6 and 70% Δ9, whereas of the adult human skin surface sterol ester fatty acids 89% were Δ6 and 11% Δ9. Chain extension was particularly pronounced in the sterol ester fatty acid monoenes of vernix caseosa amounting to 7–8 C₂ units in some cases. The fatty acids of the sterol esters of both vernix caseosa and adult human skin surface appear to be derived from the sebaceous gland and from the keratinizing epidermis, but those of the wax esters are from the sebaceous glands only.     

Biosynthesis of lipids by bovine meibomian glands

Isolated bovine meibomian glands incorporated exogenous [1-¹⁴C] acetate into lipids. Thin layer chromatographic analysis of the lipids showed that wax esters and sterol esters contained 61% of the total label. Radio gas liquid chromatographic analysis of the acid and alcohol moieties of both ester fractions showed the label was distributed equally between the two portions of the ester in both cases. Cholesterol and 5-α-cholest-7-en-3β-ol were the major labeled sterols, and anteiso-C25, anteiso-C27 and anteiso-C23 were the most highly labeled alcohols. The major labeled fatty acids in the wax esters were anteiso-C15,n-C16, anteiso-C17 andn-C18∶1, whereas anteiso-C25 and anteiso-C27 were the major labeled acids in the sterol esters. The diester region with 6% of the total label contained labeled fatty acids and fatty alcohols each with anteiso-C25 as the major component and ω-hydroxy acids in whichn-C32∶1 was the major labeled component. The trigly ceride fraction which contained 8% of the total lipids was composed of labeled fatty acids similar to those found in both sterol and wax ester fractions. Chromatographic analyses of the labeled lipids derived from exogenous labeled isoleucine showed that anteiso-branched products were preferentially labeled. The labeled triglyceride fraction derived from [U-¹⁴C] isoleucine also contained esterified C15, C13, C11, C9, C7 and possibly shorter anteisobranched acids.     

Wax esters in the cystacanths ofPolymorphus minutus (Acanthocephala)

The lipids of the cystacanth of the acanthocephalanPolymorphus minutus have been analyzed. Wax esters constituted nearly 90% of the total cystacanth lipids. The wax ester fraction contained approximately 10% steroid ester; the rest was long chain alcohols C₁₂ to C₂₀, largely saturated, esterified with fatty acids C₁₂ to C₂₂, mostly unsaturated, with C₁₈ predominating. Corresponding quantities of wax esters were not found in the adult parasite. Cholesterol was identified as the only steroid present in the cystacanth.     

The high content of monoene fatty acids in the lipids of some midwater fishes: Family myctophidae

The total lipids of eleven species of Myctophids caught at depths between 20 and 700 m in the northern Pacific Ocean were analyzed using silicic acid column chromatography (lipid classes) and capillary gas chromatography (fatty acid and fatty alcohol composition). The major components in the lipid classes were triacylglycerols or wax esters; triacylglycerols were the dominant acyl neutral lipids (68.1–96.1%) in eight species, and wax esters were found as the dominant lipid (85.5–87.9%) in three species. The major fatty acids and alcohols contained in the was esters of the three fishes were 18:1n–9, 20:1n–9, 20:1n–11, and 22:1n–11 for fatty acids, and 16:0, 18:1, 20:1, and 22:1 for fatty alcohols. Fatty acids in the triacylglycerols ranging from C₁₄ to C₂₂ were predominantly of even chain length. The major components were 16:0, 16:1n–7, 18:1n–9, 20:1n–11, 22:1n–11, 20:5n–3 (icosapentaenoic acid), and 22:6n–3 (docosahexaenoic acid). In both the triacylglycerols and the wax esters, the major fatty components were monoenoic acids and alcohols. It is suggested from the lipid chemistry of the Myctophids that they may prey on the same organisms as the certain pelagic fishes such as saury and herring, because the large quantities of monoenoic fatty acids are similar to those of saury, herring, and sprats whose lipids originate from their prey organisms such as zooplanktons which are rich in monoenoic wax esters.     

Proportions of C18∶1n−7 and C18∶1n−9 fatty acids in canola seedcoat surface and internal lipids

Lipids of canola seedcoats (Brassica napus L. andB. rapa L.) were prepared by surface washing and by complete extraction of seed coats with toluene. The major fatty acyl-containing triacylglycerols, wax esters and free fatty acids were separated by thin-layer chromatography prior to transesterification and analysis by gas-liquid chromatography. The proportion of C18∶1n−7 to C18∶1n−9 was higher in the extracted lipids than in the surface-washed lipids for all three classes.     

The lipids of the common house cricket,Acheta domesticus L. I. Lipid classes and fatty acid distribution

The lipids of the common house cricket,Acheta domesticus L., have been examined with the following results. The fatty acids associated with the lipid extracts do not change significantly from the third through the eleventh week of the crickets' postembryonic life. The major fatty acids are linoleic (30–40%), oleic (23–27%), palmitic (24–30%), and stearic acids (7–11%). There are smaller amounts of palmitoleic (3–4%), myristic (∼1%), and linolenic acids (<1%). The fatty acid composition of the cricket lipids reflects but is not identical to the fatty acids of the dietary lipids: linoleic (53%), oleic (24%), palmitic (15%), stearic (3%), myristic (2%), and linolenic acid (2%). The amount of triglycerides present in the crickets increases steadily from the second through the seventh or eighth week of postembryonic life, then drops sharply. Other lipid classes, such as hydrocarbons, simple esters, diglycerides, monoglycerides, sterols, and free fatty acids remain about constant. The composition of the fatty acids associated with the tri-, di-, and monoglycerides and the free fatty acid fraction are all about the same. The fatty acids associated with the simple esters are high in stearic acid. Postdoctoral Research Associate, Department of Chemistry, University of Michigan, 1965–1967.