Andrey B. Imbs

Determination of food sources of marine invertebrates from a subtidal sand community using analyses of fatty acids and stable isotopes

The fatty acid compositions and stable isotope ratios of carbon, nitrogen, and sulfur were analyzed in the bivalve mollusks Mactra chinensis, Pandora pulchella, Felaniella usta, and Megangulus zyonoensis, the polychaete Chaetopterus cautus, and the main sources of organic matter in a subtidal sand bottom community in Vostok Bay (Sea of Japan). The fatty acid composition and stable isotope ratios of some bivalves is likely to be indicative of substantial inputs from benthic microalgae and an important role of microbial food chains. Only the filter-feeding polychaete C. cautus showed similarity in these characteristics to suspended particulate organic matter synthesized by phytoplankton. It is suggested that the contribution of benthic microalgae to the diet of a consumer organism, inferred solely from the carbon stable isotope analysis, can be significantly overestimated.

Response of prostaglandin content in the red alga Gracilaria verrucosa to season and solar irradiance

The influence of solar irradiance and seasons on prostaglandin (PG) and arachidonic acid (AA) content in the marine red alga Gracilaria verrucosa (Huds.) Papenf. (unattached form) was investigated. PGA(2), PGE(2), PGF(2), and 15-keto-PGE(2) were isolated from the alga, quantitatively analyzed as 4-methyl-7-methoxycoumarin esters by high-performance liquid chromatography, and their chemical structures were confirmed by 1H NMR. In June-September, the PG content in the alga was relatively stable (420 microg/g of dry wt. of PGE(2)+PGF(2); 40 microg/g of PGA(2)) and it increased 1.5 times in October. The highest level of PGs was detected in November (2500 microg/g of PGE(2)+PGF(2); 74 microg/g of PGA(2)) when water temperature was fairly low (5-10 degrees C). Algae grown for five months at 50% of incident photosynthetic active radiation (PAR(0)) contained two times less PGE(2) and PGF(2) than algae grown under natural conditions, but the amount of these PG in algae grown at 5% of PAR(0) was close to the normal level. On the contrary, when algae were grown at 5% of PAR(0) the content of PGA(2) increased up to 4 times compared to algae cultivated at 100% PAR(0). In June-November, the amount of AA in total algal lipids slightly varied from 48.9 to 56.7% and did not virtually depend on the light intensity. The probable reasons of the PG content variation in response to environmental factors are discussed.

DIET-INDUCED CHANGES IN LIPID AND FATTY ACID COMPOSITION OF ARTEMIA SALINA

The influence of diet on lipid and fatty acid composition of the brine shrimp Artemia salina nauplii was investigated. Various diets with different lipid composition and fatty acid profiles were fed to nauplii for 2 weeks. The lipid composition of microalgal diets, Isochrysis galbana, Phaeodactylum tricornutum and Nannochloropsis oculata and bakers yeast was analyzed. Newly hatched nauplii were examined before the feeding experiment. It was shown that Artemia was able to incorporate and selectively concentrate some dietary lipids. Depot lipids were more sensitive to changes in the dietary lipid composition than the main structural lipids, polar lipids and sterols. Variations in the content of the lipid classes correlated with stage of development of the animal. The fatty acid composition of the animal varied with that of diet. The concentrations of saturated fatty acids were apparently supported in the nauplii by biosynthesis de novo. The acid 16:1(n-7) originated from the food. The concentration range of n-6 polyunsaturated fatty acids (PUFAs) remained constant through the accumulation from the diet. The proportion of n-3 PUFAs varied with their level in the diet. The dynamics of alteration of 20:5(n-3) content in Artemia fed on Isochrysis, which is poor in this acid, suggested a limited capacity for elongation and desaturation of 18:3(n-3) to 20:5(n-3). None of the diets provided dietary input of 22:6(n-3)

Diversity of fatty acid composition of symbiotic dinoflagellates in corals: Evidence for the transfer of host PUFAs to the symbionts

High diversity of fatty acid (FA) composition of endosymbiotic dinoflagellates of the Symbiodinium group (zooxanthellae) isolated from different cnidarian groups has been found. To explain this diversity, FA composition of the total lipids of pure symbiont fractions (SF) and host cell tissue fractions (HF) isolated from one hydrocoral, two soft coral, and seven hard coral species inhabiting the shallow waters of the South China Sea (Vietnam) were compared. Symbiodinium phylogenetic clade designation for each SF was also determined, however, the relationship between the clade designation and FA composition of Symbiodinium was not found. The profiles of marker polyunsaturated FAs (PUFAs) of symbionts (18:4n-3, 18:5n-3, 20:5n-3) did not depend on taxonomic designation of the host and reflected only a specimen-specific diversity of the SF lipids. Several FAs such as 20:0, C24 PUFAs, 22:5n-6, and 18:2n-7 concentrated in HF lipids but were also found in SF lipids. For ten cnidarian species studied, the principal components analysis of total FAs (27 variables) of the symbiotic fractions was performed. The clear division of the symbiotic dinoflagellates according to the host systematic identity was found on a subclass level. This division was mainly caused by the FAs specific for the host lipids of each cnidarian subclasses such as hard corals, soft corals, and hydrocorals. Thus, the coral hosts affect the FA profile of their symbionts and cause the diversity of FA composition of Symbiodinium. The transfer of FAs from the coral host to their symbiotic dinoflagellates and modulation of PUFA biosynthesis in symbionts by the host are considered as possible reasons of the diversity studied.

Application of Fatty Acids for Chemotaxonomy of Reef-Building Corals

Sixteen scleractinian species of six coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Pectiniidae, and Fungiidae) from Vietnam were analyzed for fatty acid (FA) composition. Except for the Poritidae species, total lipids of the corals had the same set of FAs, about 50% of them being unsaturated acids. Some coral families had high levels of characteristic FAs: 20:3(n-6), 20:4(n-3), and 22:6(n-3) in Pocilloporidae; 18:1(n-9) and 22:6(n-3) in Poritidae; and 18:3(n-6) and 22:5(n-3) in Faviidae. For the first time in hexacorals, unsaturated C24 FAs (24:1(n-9), 24:2(n-6), 24:2(5,9), 24:3(5,9,17), and 24:4(n-3)) were discovered in the Poritidae species. The highest level of 18:1(n-7), odd-chain and branched FAs (7.5% in total) was detected in Sandalolitha robusta. The data obtained on the contents of ten principal C18–C22 polyunsaturated FAs (PUFAs) for the 16 specimens were combined with data on the 19 reef-building coral specimens investigated previously and subjected to multidimensional scale analysis (MSA). The representative coral families (Acroporidae, Pocilloporidae, Poritidae, Faviidae, Dendrophylliidae, and Milleporidae) were separated by MSA according to the composition of their principal PUFAs. Therefore, PUFAs may serve as chemotaxonomic markers for reef-building corals at the family level. Family-specific compositions of coral zooxanthellae characterized by different PUFA profiles, which affect the PUFA content of whole coral colonies, were supposed to be the probable cause of the discovered chemotaxonomic distinctions between reef-building corals.

Lipid Class and Fatty Acid Composition of the Boreal Soft Coral Gersemia rubiformis

Total lipid, phospholipid, and FA composition and distribution of FA between polar lipids (PL) and neutral lipids (NL) were investigated in the boreal soft coral Gersemia rubiformis from the Bering Sea. The total lipids were mostly hydrocarbons and waxes (33.7%) and PL (33.1%). The content of monoalkyldiacylglycerols (9.7%) exceeded the content of TAG (6.7%). PC and PE constituted 31.4% and 25.6% of total phospholipids, respectively. Principal FA were 16∶0, 16∶1n−7, 18∶0, 18∶1n−9, 18∶1n−7, 20∶1n−7, 20∶4n−6, 20∶4n−3, 20∶5n−3 22∶5n−3, 22∶6n−3, 24∶5n−6, and 24∶6n−3. Most n−6 PUFA (52% of total FA) were associated with the PL fraction; this was especially true for arachidonic and tetracosapentaenoic acids. The NL were enriched with mono-, di-, trienoic, and n−3 PUFA. The variation in EPA levels in both NL and PL suggests an origin of this acid from lipids of diatoms consumed by the corals.

Fatty acids and other lipids of corals: Composition, distribution, and biosynthesis

This paper reviews the literature data on the composition, structure, and distribution of the main lipid classes and their fatty acids in reef-building and soft corals and in hydrocorals of the genus Millepora. The review presents information about more than 150 coral species from tropical and cold waters of the World Ocean, as well as data on the influence of environmental factors on the lipid compositions of corals. The possible pathways of polyunsaturated fatty acid biosynthesis in corals are discussed.

Biosynthesis of polyunsaturated fatty acids in zooxanthellae and polyps of corals

The fatty acid (FA) composition of zooxanthellae, polyp tissue, and intact colonies was determined in soft coral Sinularia sp. and hard coral Acropora sp. Analysis of the distribution of polyunsaturated fatty acids (PUFAs) among the zooxanthellae and the host organism showed that 18: 3n-6 and C18–22 PUFAs of the n-3 series (18: 4n-3, 20: 5n-3, 22: 5n-3, and 22: 6n-3) were mainly synthesized by the zooxanthellae and that C20–22 PUFAs of the n-6 series (20: 3n-6, 20: 4n-6, and 22: 4n-6) were synthesized in the polyp tissue. Soft coral polyps were able to synthesize tetracosapolyenoic FAs (24: 5n-6 and 24: 6n-3) and 18: 2n-7, their zooxanthellae synthesized C16 PUFAs (16: 2n-7, 16: 3n-4, and 16: 4n-1). It is supposed that the biosynthesis of 16: 2n-7 in Sinularia sp. and 18: 3n-6 in Acropora sp. is catalyzed by Δ6 desaturase. The relatively even distribution of three FAs (18: 2n-6, 18: 3n-6, and 16: 2n-7) among lipids of zooxanthellae and coral polyps indicates the possible transport of these FAs between symbionts and the host organism.

Fatty acids and triacylglycerols in seeds of Pinaceae species

Abstract The fatty acid and fully hydrogenated triacylglycerol composition in the seeds of Pinus massoniana, P. merkusii, P. caribea, P. kesyia, P. dalatensis, P. krempfii, P. koraiensis and P. siberya were determined. The non-methylene-interrupted polyenoic fatty acids amounted to 12.0–26.4% of total acids. The distribution of triacylglycerols of the seeds according to their molecular weights was similar to that of common seed oil. The possible chemosystematic application of the fatty acid composition of seeds of Pinaceae is discussed.

Trans-olefinic very-long-chain patty acid (26:3Δ5c,9c,19t) in lipids of fresh-water sponges of lake baikal

Abstract A novel trans-olefinic very -long-chain fatty acid was found in the lipids of the Lake Baikal sponges. It has a structure of 26:3 5c,9c,19t, as shown by chemical and instrumental methods.