Prog. I.Jptd Res. Vol. 18. pp I to 30. ¢) Pergamon Press Lid 1979. Printed in Great Britain
0)63-7827/79/0701-0001505.00/0
LIPID COMPOSITION OF MARINE AND ESTUARINE INVERTEBRATES: PORIFERA AND CNIDARIA JEANNE D. JOSEPH* South Carolina Marine Resources Center, Marine Resources Research Institute, P.O. Box 12559. Charleston, South Carolina 29412, U.S.A.
CONTENTS I. II.
1II.
INTRODUCTION
l
THE MARINE FOOD WEB PHYLUM PORIFERA
3
A. Lipid content and class composition B. Neutral lipids 1. Aliphatic fatty acids 2. Aromatic acids, esters and aldehydes C. Polar lipids I, Phospholipids 2. Phosphonolipids 3. Glycolipids IV.
PHYLUM CNIDARIA
|I
A. Lipid content and class composition 1. Hydrozoa 2. Scyphozoa 3. Anthozoa B. Neutral lipids 1. Hydrocarbons (a) Hydrozoa (b) Anthozoa 2. Fatty acids (a) Hydrozoa (b) Scyphozoa (c) Anthozoa (d) Cubozoa 3. Wax esters and alcohols (a) Hydrozoa
12 12 13 14 15 15 15 15 16 16 17 20 21 24
(b) Anthozoa 4. Alkyldiacylglycerols and glyceryl ethers
C. Polar lipids 1. Phospholipids 2. Phosphonolipids 3. Glycolipids V.
3 3 3 7 9 9 11 11
24 24 24
25 25 25 27
SUMMARY
27
REFERENCES
28
!. I N T R O D U C T I O N A n u m b e r of recently p u b l i s h e d reviews testify to the increased interest o f c h e m i s t s in lipids of m a r i n e a n i m a l s , b o t h v e r t e b r a t e s a n d invertebrates. This interest has been s t i m u l a t e d by such factors as the search for new p r o t e i n s o u r c e s a n d drugs, r e c o g n i t i o n o f the i m p o r t a n c e o f p o l y u n s a t u r a t e d fatty a c i d s in h u m a n h e a l t h a n d n u t r i t i o n , c o n c e r n for c o n t a m i n a t i o n o f sea f o o d s by pesticides a n d c h l o r i n a t e d h y d r o c a r b o n s a n d c e r t a i n l y *Present address: U.S. Department of Commerce, National Oceanic and Atmospheric Administration. National Marine Fisheries Service, Charleston Laboratory, P.O. Box 12607, Charleston, South Carolina 29412. U.S.A. LF'.L.R. 181--^
|
2
Jeanne D. Joseph
by the development o f modern, analytic technology. Reviews by Lovern s6 in 1964 and Malins and Wekell a7 in 1970, both of which indicated large untapped areas of knowledge in this discipline, have also probably played a role in enhancing research efforts in this field. A recent review by Morris and Culkin stressed current methodology in marine lipid research and described the fatty acid composition of representative marine organisms. 99 Another review emphasized lipid transfer in the marine food chain, ~19 more aptly termed a food "web" because of the complex trophic interrelationships which exist in the aquatic environment. Three up-to-date reviews on sterols of marine organisms are available, '~°'1°°'112 and this class of lipids will not, therefore, be considered in this review. Spectacular advances in gas-liquid chromatography (GLC) since James and Martin first described its use in fatty acid separation, 54 and recent progress in mass spectrometry (MS) and nuclear magnetic resonance spectrometry (NMR) have made possible the structural description of minute quantities of lipids and other natural products. This is of enormous benefit to the marine lipid chemist because, as will be shown, many marine invertebrates contain little lipid and individual lipid classes may be present only in trace amounts. Since it is difficult to compare results obtained by modern technology with those obtained by earlier methodology, this review will be limited, largely, to studies which have utilized modern chromatographic and spectrometric methods. The fatty acid nomenclature employed in this review for mono~noic and methyleneinterrupted polyunsaturated fatty acids has been suggested by the IUPAC-IUB Commission on Biochemical Nomenclature s3 as a replacement for the "~o" system, widely in use for a number of years. There is, however, no basic difference in the two systems, as both are based upon the position of the terminal olefinic bond with reference to the nonpolar end of the molecule, i.e. the end carbon chain. Either system is very convenient in discussions of fatty acid biosynthesis by chain-elongation and desaturation since, in this process, the end carbon chain is unaltered and fatty acid family relationships are clarified. These systems also form the basis for semi-log plotting techniques and calculations widely used in the identification of fatty acids separated by G L C . 3-5'55 For nonmethylene-interrupted polyunsaturates, this system cannot be used and the positions of the double bonds within the molecule must be specified. In this review, fatty acids of this type are identified by the number of carbons in the chain followed by the number of double bonds, the symbol A, and the positions of the double bonds relative to the carboxyl group of the molecule. II. T H E M A R I N E
FOOD
WEB
Sargent's recent review '~9 has made a detailed discussion of the marine food web unnecessary, particularly since transfer of fatty acids and other lipids from prey to predator is w e l l - d o c u m e n t e d . 23"25-27'38"59"6''65"79"92A°5'1°6 However, in addition to predator-prey relationships, it should be recognized that dissolved and particulate organics may contribute significantly to the nutrition of aquatic organisms. Several analyses have shown that fatty acids and other lipids are dissolved in varying amounts in sea water 12'57"93"1°'*'127A39 and others have demonstrated that these compounds can be taken up and metabolized by marine invertebrates. 2s'39''ts'131 Particulate lipids. adsorbed onto or contained in detrital materiai.~ 23.124.139 or in more-or-less pure form such as Bute Inlet wax' s.76 and ocean slicks of biological origin, t s.so may be important energy sources for marine animals. Corals exude a mucus, rich in wax-esters which is avidly fed upon by reef fishes. 1a'19 Symbiosis is another factor complicating the food web and also, incidentally, complicating biochemical analyses of marine invertebrates. In shallow, tropical seas, many invertebrates, particularly cnidarians and sponges, are hosts for photosynthetic zooxanthellae.lS,11o,134,~35 The importance of this relationship for the coral, Pocillopora capitata, was demonstrated by Patton et al., who showed that the algal symbionts take carbon derived from the host and synthesize fatty acids which are then returned to
Lipid composition of marine and estuarine invertebrates
3
the coral for its use in biosynthesis of wax esters and triacylglycerols.~ ° von Holt and yon Holt have noted a similar, facile transfer of organics from zooxanthellae to their cnidarian hosts. ~3s Clearly, interpretation of analytic data must take into account these facets of the marine food web as well as the more obvious effects of direct dietary transfer from prey to predator, many of which are, unfortunately, largely unknown. IlL P H Y L U M P O R I F E R A
Sponges are the most primitive of the Metazoa (multicellular animals) and lack both specialized tissues and organs. Almost all sponges are sessile and may be found wherever a suitable stratum for attachment is present. Their physiology is entirely dependent upon the circulation of water through numerous body chambers, canals and pores which they are able to control, to some degree. Sponges are filter-feeders and 80% of the available organic matter which they consume is sub-microscopic in size, the remaining 20% consisting of smaller plankton such as dinoflagellates and bacteria. 17 It is possible that dissolved organics may be very important in the nutrition of these animals. The only class of sponges for which published data are available is the Demospongiae. No information is available on the Calcarea or the Hexactinellida. The Hexactinellida are, for the most part, deep water sponges living at a depth of 450-900 m, although there are also abyssal dwellers. 17 The Calcarea are available to the chemist as they generally inhabit the shallow coastal waters. However, as Litchfield et al. have noted, s3 they are frequently heavily contaminated with algae and biochemical analyses would give spurious results.
A. Lipid Content and Class Composition Sponges have no adipose tissues and, consequently, their lipid content (percent of wet weight) is very low. Litchfield and his co-workers have reported lipid levels varying from 0.5% to 1.5% in a number of species. 56"s3"9"t Lipid class composition of eight species of Kenyan sponges has been described by Marsden (Table 1).ss Sterols and phospholipids were present in all species but wax esters and fatty acids in none. Only one species, Ceratochalina sp., contained no steryl esters. Considerable variation in composition between species and between individuals of the same species was observed for the other lipid classes. Two species, Craniella australiensis and Raphisia sp., consistently lacked triacylglycerols, although other glycerides, glyceryl ether diesters (alkyl diacylglycerols), neutral plasmalogens (alkenyl diacylglycerols), mono- and/or diacylglycerols were present. Plasmalogens were identified through the use of Schiff reagent, lsay et al. reported the presence of glyceryl ethers (0.4-3.7%) in hydrolyzed lipids of three unidentified species of Demospongiae. s2 Marsden's analyses of sponges kept alive until extracted suggests that unesterified fatty acids are normally not present in lipids of living sponges, ss However, it has been reported that lipid of the outer tissues of the freshwater sponge, SponoiUa waoneri, is rich in fatty acids. 74 The principal lipid classes observed in Microcliona prolifera were structural lipids: sterols, steryl esters, phosphatidylcholine, phosDhatidylethanolamine and phosphatidylserine, s6.ss.97
B. Neutral Lipids I. Aliphatic Fatty Acids Bergmann and Swift were first to report the presence of high molecular weight fatty acids in sponges. 21 Recent studies by Litchfield and his colleagues have confirmed this observation and their work indicates that very long-chained-(C24-Cso) saturated and olefinic fatty acids may be characteristic of the Demospongiae. 56,s3-sS'96-gs For this
"Individual or seasonal variation.
Steryl e s t e r s Wax esters Alkyl diacylglycerols Alkenyl diacylglycerols Triacylglyeerols Diacylglycerols Monoacylglycerols Fatty acids Sterois Phospholipids Plasma Iogens
L i p i d class + . ? _+ .~ + + + . + + -
Spiraslella im'onstans
.
.
I.
+ + +
.
. + + +
_ + _
-
+
+ + +
. _+
. -
-
+
sp.
.
Craniella australiensis
Lipid Class Composition
Laxosuherites
TAnt~l~
. + + .+
+ + +
-
_
+
sp.
Pseuduxinella
+ + +
_ + +
+
+
+
sp.
Raphisia
o f M a r i n e S p o n g e s as
+ + _
+ + +
-
-
+
Clalharia t)'pica
+ + _
+ + +
?
+_ _+ + +
+ + _ _
+
Sionuad~x.ia s)'mbotica
_
_
sp.
Ceratochalma
Lipid composition TAnL[
2. M a j o r
Saturated,
Monoenoic
of marine and
and estuarine
Methylene-interrupted
5
invertebrates Polyunsaturated
Fatty
Acids
of
M.
prolifera 9~ Weight
percent composition" 20
Chain-length
16
18
Saturates M onoenes
4.1
2.1
0.1 0.6 0.3
tr. h 3.3 0.3 .
tr. ----
-0.2 ---
tr. 0.2 tr. --
tr. tr. -tr.
--
O. 1 0.1 --0.6 1.8 ---
O. I -1.1 --
0. I
0. 3
1.6
0.2
0.2 0.7 0.1
--0.2
--0.2
0.1 3.6 --
1.7 15.4
---
---
~n-5) (n-7) (n-91 (n-lO} (n-I 1) (n-13} (n-15] In-17)
tr.
22
24
26
0.8
3.0
1.9
0.1
-0.3 0. t
tr.
--
--
0.4
2.2
1.6
4.0 0.4
--
0.1
-0.1 tr.
--0.6
.
0. I .
.
.
Polyunsaturates
2 3 4 5 3 4 5 6
(n-6) (n-6) (n-6) (n-6) (n-3) (n-3) (n-3) (n-3)
------
"Total fatty acids reported b'rrace a m o u n t ( < 0.1%).
included
33.0% nonmethylene-interrupted
fatty acids.
reason, they proposed the name "demospongic acids" as a convenient term of reference. s3 Analyses of fatty acids from 18 species of sponges demonstrated the presence of high levels of demospongic fatty a ~ d s . s3 Of these species, Athosiomella mrkms con. rained the smallest percentage of these long-chained acids (34%) and Cliona celata the greatest (79%). The average value for all species was 54%. Five species, Lissodendoryx sp., Tedania k3nis, Haliclona oculata, Sponoilla lacustris and C. celata, contained a saturated fatty acid which had an equivalent chain length (ECL) of 23.41-23.47 on a 10% EGSS-X column, possibly iso 24:0. Even more unusual, a peak with ECL 24,48 was observed in chromatograms of Spon0ia sp. hydrogenated fatty acids and comprised 24% of the total area. s3 More recent research on the fatty acids of M. prolifera by this team of investigators has provided considerable information on their structure and biosynthesis in sponges.Se '97'9e In this particular species, a total of 118 fatty acids, including positional isomers, were identified by AgNO3/TLC isolation, degradative techniques and GLC; of these, 95 were present in amounts of 0.1% or more. 97 In addition to fatty acids commonly found in most marine animals, these authors observed C22, C24 and C2e methylene-interrupted acids which probably arise from chain-elongation of dietary 18:2 (n-6) and 18:3 (n-3) (Table 2). 97 Nonmethylene-interrupted (NMI) acids were unsaturated at the 5 and 9 positions ifi the molecule and those specifically identified were 24:2A5,9; 25:2A5,9, 26:2A5,9; 26:3A5,9,17; 26:3A5,9,19, 27:3A5,9,19 and 27:3A5,9,20. Figure 1 illustrates the major NMI acids observed (and their percentages), as well as probable synthetic pathways. Although the 26:2 intermediates, shown in brackets in Fig. 1, were not found in this detailed analysis, 26:2A9,19 the .probable precursor of 26:3A5,9,19," was identified in a later study, 9s adding substantial support to the proposed pathway. The data of Table 2 and Fig. 1 indicate that chain-elongation is an active process in M. prolifera and, furthermore that, for some reason, 20:0 and 22:0 are not suitable substrates for the A9 desaturase, although the authors did note trace amounts (
0)63-7827/79/0701-0001505.00/0
LIPID COMPOSITION OF MARINE AND ESTUARINE INVERTEBRATES: PORIFERA AND CNIDARIA JEANNE D. JOSEPH* South Carolina Marine Resources Center, Marine Resources Research Institute, P.O. Box 12559. Charleston, South Carolina 29412, U.S.A.
CONTENTS I. II.
1II.
INTRODUCTION
l
THE MARINE FOOD WEB PHYLUM PORIFERA
3
A. Lipid content and class composition B. Neutral lipids 1. Aliphatic fatty acids 2. Aromatic acids, esters and aldehydes C. Polar lipids I, Phospholipids 2. Phosphonolipids 3. Glycolipids IV.
PHYLUM CNIDARIA
|I
A. Lipid content and class composition 1. Hydrozoa 2. Scyphozoa 3. Anthozoa B. Neutral lipids 1. Hydrocarbons (a) Hydrozoa (b) Anthozoa 2. Fatty acids (a) Hydrozoa (b) Scyphozoa (c) Anthozoa (d) Cubozoa 3. Wax esters and alcohols (a) Hydrozoa
12 12 13 14 15 15 15 15 16 16 17 20 21 24
(b) Anthozoa 4. Alkyldiacylglycerols and glyceryl ethers
C. Polar lipids 1. Phospholipids 2. Phosphonolipids 3. Glycolipids V.
3 3 3 7 9 9 11 11
24 24 24
25 25 25 27
SUMMARY
27
REFERENCES
28
!. I N T R O D U C T I O N A n u m b e r of recently p u b l i s h e d reviews testify to the increased interest o f c h e m i s t s in lipids of m a r i n e a n i m a l s , b o t h v e r t e b r a t e s a n d invertebrates. This interest has been s t i m u l a t e d by such factors as the search for new p r o t e i n s o u r c e s a n d drugs, r e c o g n i t i o n o f the i m p o r t a n c e o f p o l y u n s a t u r a t e d fatty a c i d s in h u m a n h e a l t h a n d n u t r i t i o n , c o n c e r n for c o n t a m i n a t i o n o f sea f o o d s by pesticides a n d c h l o r i n a t e d h y d r o c a r b o n s a n d c e r t a i n l y *Present address: U.S. Department of Commerce, National Oceanic and Atmospheric Administration. National Marine Fisheries Service, Charleston Laboratory, P.O. Box 12607, Charleston, South Carolina 29412. U.S.A. LF'.L.R. 181--^
|
2
Jeanne D. Joseph
by the development o f modern, analytic technology. Reviews by Lovern s6 in 1964 and Malins and Wekell a7 in 1970, both of which indicated large untapped areas of knowledge in this discipline, have also probably played a role in enhancing research efforts in this field. A recent review by Morris and Culkin stressed current methodology in marine lipid research and described the fatty acid composition of representative marine organisms. 99 Another review emphasized lipid transfer in the marine food chain, ~19 more aptly termed a food "web" because of the complex trophic interrelationships which exist in the aquatic environment. Three up-to-date reviews on sterols of marine organisms are available, '~°'1°°'112 and this class of lipids will not, therefore, be considered in this review. Spectacular advances in gas-liquid chromatography (GLC) since James and Martin first described its use in fatty acid separation, 54 and recent progress in mass spectrometry (MS) and nuclear magnetic resonance spectrometry (NMR) have made possible the structural description of minute quantities of lipids and other natural products. This is of enormous benefit to the marine lipid chemist because, as will be shown, many marine invertebrates contain little lipid and individual lipid classes may be present only in trace amounts. Since it is difficult to compare results obtained by modern technology with those obtained by earlier methodology, this review will be limited, largely, to studies which have utilized modern chromatographic and spectrometric methods. The fatty acid nomenclature employed in this review for mono~noic and methyleneinterrupted polyunsaturated fatty acids has been suggested by the IUPAC-IUB Commission on Biochemical Nomenclature s3 as a replacement for the "~o" system, widely in use for a number of years. There is, however, no basic difference in the two systems, as both are based upon the position of the terminal olefinic bond with reference to the nonpolar end of the molecule, i.e. the end carbon chain. Either system is very convenient in discussions of fatty acid biosynthesis by chain-elongation and desaturation since, in this process, the end carbon chain is unaltered and fatty acid family relationships are clarified. These systems also form the basis for semi-log plotting techniques and calculations widely used in the identification of fatty acids separated by G L C . 3-5'55 For nonmethylene-interrupted polyunsaturates, this system cannot be used and the positions of the double bonds within the molecule must be specified. In this review, fatty acids of this type are identified by the number of carbons in the chain followed by the number of double bonds, the symbol A, and the positions of the double bonds relative to the carboxyl group of the molecule. II. T H E M A R I N E
FOOD
WEB
Sargent's recent review '~9 has made a detailed discussion of the marine food web unnecessary, particularly since transfer of fatty acids and other lipids from prey to predator is w e l l - d o c u m e n t e d . 23"25-27'38"59"6''65"79"92A°5'1°6 However, in addition to predator-prey relationships, it should be recognized that dissolved and particulate organics may contribute significantly to the nutrition of aquatic organisms. Several analyses have shown that fatty acids and other lipids are dissolved in varying amounts in sea water 12'57"93"1°'*'127A39 and others have demonstrated that these compounds can be taken up and metabolized by marine invertebrates. 2s'39''ts'131 Particulate lipids. adsorbed onto or contained in detrital materiai.~ 23.124.139 or in more-or-less pure form such as Bute Inlet wax' s.76 and ocean slicks of biological origin, t s.so may be important energy sources for marine animals. Corals exude a mucus, rich in wax-esters which is avidly fed upon by reef fishes. 1a'19 Symbiosis is another factor complicating the food web and also, incidentally, complicating biochemical analyses of marine invertebrates. In shallow, tropical seas, many invertebrates, particularly cnidarians and sponges, are hosts for photosynthetic zooxanthellae.lS,11o,134,~35 The importance of this relationship for the coral, Pocillopora capitata, was demonstrated by Patton et al., who showed that the algal symbionts take carbon derived from the host and synthesize fatty acids which are then returned to
Lipid composition of marine and estuarine invertebrates
3
the coral for its use in biosynthesis of wax esters and triacylglycerols.~ ° von Holt and yon Holt have noted a similar, facile transfer of organics from zooxanthellae to their cnidarian hosts. ~3s Clearly, interpretation of analytic data must take into account these facets of the marine food web as well as the more obvious effects of direct dietary transfer from prey to predator, many of which are, unfortunately, largely unknown. IlL P H Y L U M P O R I F E R A
Sponges are the most primitive of the Metazoa (multicellular animals) and lack both specialized tissues and organs. Almost all sponges are sessile and may be found wherever a suitable stratum for attachment is present. Their physiology is entirely dependent upon the circulation of water through numerous body chambers, canals and pores which they are able to control, to some degree. Sponges are filter-feeders and 80% of the available organic matter which they consume is sub-microscopic in size, the remaining 20% consisting of smaller plankton such as dinoflagellates and bacteria. 17 It is possible that dissolved organics may be very important in the nutrition of these animals. The only class of sponges for which published data are available is the Demospongiae. No information is available on the Calcarea or the Hexactinellida. The Hexactinellida are, for the most part, deep water sponges living at a depth of 450-900 m, although there are also abyssal dwellers. 17 The Calcarea are available to the chemist as they generally inhabit the shallow coastal waters. However, as Litchfield et al. have noted, s3 they are frequently heavily contaminated with algae and biochemical analyses would give spurious results.
A. Lipid Content and Class Composition Sponges have no adipose tissues and, consequently, their lipid content (percent of wet weight) is very low. Litchfield and his co-workers have reported lipid levels varying from 0.5% to 1.5% in a number of species. 56"s3"9"t Lipid class composition of eight species of Kenyan sponges has been described by Marsden (Table 1).ss Sterols and phospholipids were present in all species but wax esters and fatty acids in none. Only one species, Ceratochalina sp., contained no steryl esters. Considerable variation in composition between species and between individuals of the same species was observed for the other lipid classes. Two species, Craniella australiensis and Raphisia sp., consistently lacked triacylglycerols, although other glycerides, glyceryl ether diesters (alkyl diacylglycerols), neutral plasmalogens (alkenyl diacylglycerols), mono- and/or diacylglycerols were present. Plasmalogens were identified through the use of Schiff reagent, lsay et al. reported the presence of glyceryl ethers (0.4-3.7%) in hydrolyzed lipids of three unidentified species of Demospongiae. s2 Marsden's analyses of sponges kept alive until extracted suggests that unesterified fatty acids are normally not present in lipids of living sponges, ss However, it has been reported that lipid of the outer tissues of the freshwater sponge, SponoiUa waoneri, is rich in fatty acids. 74 The principal lipid classes observed in Microcliona prolifera were structural lipids: sterols, steryl esters, phosphatidylcholine, phosDhatidylethanolamine and phosphatidylserine, s6.ss.97
B. Neutral Lipids I. Aliphatic Fatty Acids Bergmann and Swift were first to report the presence of high molecular weight fatty acids in sponges. 21 Recent studies by Litchfield and his colleagues have confirmed this observation and their work indicates that very long-chained-(C24-Cso) saturated and olefinic fatty acids may be characteristic of the Demospongiae. 56,s3-sS'96-gs For this
"Individual or seasonal variation.
Steryl e s t e r s Wax esters Alkyl diacylglycerols Alkenyl diacylglycerols Triacylglyeerols Diacylglycerols Monoacylglycerols Fatty acids Sterois Phospholipids Plasma Iogens
L i p i d class + . ? _+ .~ + + + . + + -
Spiraslella im'onstans
.
.
I.
+ + +
.
. + + +
_ + _
-
+
+ + +
. _+
. -
-
+
sp.
.
Craniella australiensis
Lipid Class Composition
Laxosuherites
TAnt~l~
. + + .+
+ + +
-
_
+
sp.
Pseuduxinella
+ + +
_ + +
+
+
+
sp.
Raphisia
o f M a r i n e S p o n g e s as
+ + _
+ + +
-
-
+
Clalharia t)'pica
+ + _
+ + +
?
+_ _+ + +
+ + _ _
+
Sionuad~x.ia s)'mbotica
_
_
sp.
Ceratochalma
Lipid composition TAnL[
2. M a j o r
Saturated,
Monoenoic
of marine and
and estuarine
Methylene-interrupted
5
invertebrates Polyunsaturated
Fatty
Acids
of
M.
prolifera 9~ Weight
percent composition" 20
Chain-length
16
18
Saturates M onoenes
4.1
2.1
0.1 0.6 0.3
tr. h 3.3 0.3 .
tr. ----
-0.2 ---
tr. 0.2 tr. --
tr. tr. -tr.
--
O. 1 0.1 --0.6 1.8 ---
O. I -1.1 --
0. I
0. 3
1.6
0.2
0.2 0.7 0.1
--0.2
--0.2
0.1 3.6 --
1.7 15.4
---
---
~n-5) (n-7) (n-91 (n-lO} (n-I 1) (n-13} (n-15] In-17)
tr.
22
24
26
0.8
3.0
1.9
0.1
-0.3 0. t
tr.
--
--
0.4
2.2
1.6
4.0 0.4
--
0.1
-0.1 tr.
--0.6
.
0. I .
.
.
Polyunsaturates
2 3 4 5 3 4 5 6
(n-6) (n-6) (n-6) (n-6) (n-3) (n-3) (n-3) (n-3)
------
"Total fatty acids reported b'rrace a m o u n t ( < 0.1%).
included
33.0% nonmethylene-interrupted
fatty acids.
reason, they proposed the name "demospongic acids" as a convenient term of reference. s3 Analyses of fatty acids from 18 species of sponges demonstrated the presence of high levels of demospongic fatty a ~ d s . s3 Of these species, Athosiomella mrkms con. rained the smallest percentage of these long-chained acids (34%) and Cliona celata the greatest (79%). The average value for all species was 54%. Five species, Lissodendoryx sp., Tedania k3nis, Haliclona oculata, Sponoilla lacustris and C. celata, contained a saturated fatty acid which had an equivalent chain length (ECL) of 23.41-23.47 on a 10% EGSS-X column, possibly iso 24:0. Even more unusual, a peak with ECL 24,48 was observed in chromatograms of Spon0ia sp. hydrogenated fatty acids and comprised 24% of the total area. s3 More recent research on the fatty acids of M. prolifera by this team of investigators has provided considerable information on their structure and biosynthesis in sponges.Se '97'9e In this particular species, a total of 118 fatty acids, including positional isomers, were identified by AgNO3/TLC isolation, degradative techniques and GLC; of these, 95 were present in amounts of 0.1% or more. 97 In addition to fatty acids commonly found in most marine animals, these authors observed C22, C24 and C2e methylene-interrupted acids which probably arise from chain-elongation of dietary 18:2 (n-6) and 18:3 (n-3) (Table 2). 97 Nonmethylene-interrupted (NMI) acids were unsaturated at the 5 and 9 positions ifi the molecule and those specifically identified were 24:2A5,9; 25:2A5,9, 26:2A5,9; 26:3A5,9,17; 26:3A5,9,19, 27:3A5,9,19 and 27:3A5,9,20. Figure 1 illustrates the major NMI acids observed (and their percentages), as well as probable synthetic pathways. Although the 26:2 intermediates, shown in brackets in Fig. 1, were not found in this detailed analysis, 26:2A9,19 the .probable precursor of 26:3A5,9,19," was identified in a later study, 9s adding substantial support to the proposed pathway. The data of Table 2 and Fig. 1 indicate that chain-elongation is an active process in M. prolifera and, furthermore that, for some reason, 20:0 and 22:0 are not suitable substrates for the A9 desaturase, although the authors did note trace amounts (
