Crabs Eriocheir japonica and Paralithodes camtschaticus Are a Rich Source of Lipid Molecular Species with High Nutritional Value.

Due to their valuable meat and hepatopancreas, the world's most famous delicacies, crabs, have become target species of commercial fisheries and aquaculture. By methods of supercritical fluid and high-performance liquid chromatography, coupled with high resolution mass spectrometry, we analyzed triacylglycerols (TG) and phospholipids (PL)-glycerophosphoethanolamines (PE), glycerophosphocholines (PC), glycerophosphoserines (PS), and glycerophosphoinositols (PI)-in the hepatopancreas and muscles of the Japanese mitten crab Eriocheir japonica and the red king crab Paralithodes camtschaticus inhabiting the Sea of Japan. TGs were the main class of lipids in the crab hepatopancreas, while they were found in trace amounts in muscle. TGs of E. japonica differed from those of P. camtschaticus by a higher content of 16:0, 16:1, 18:2, and 20:4 FA and a lower content of eicosapentaenoic and docosahexaenoic acids. The Japanese mitten crab differed from the red king crab by a lower content of molecular species with eicosapentaenoic acid in PC and PI; an increased content of arachidonic acid in PE, PS, and PI; and a lower content of molecular species with docosahexaenoic acid in PE in the hepatopancreas and muscles. The high nutritional value of the crabs E. japonica and P. camtschaticus was confirmed by a high content of molecular species of lipids with n-3 polyunsaturated fatty acids. The data of the lipid molecular species profile provide new background information for future studies on biochemistry and aquaculture of crabs.

Coral Lipidome: Molecular Species of Phospholipids, Glycolipids, Betaine Lipids, and Sphingophosphonolipids.

Coral reefs are the most biodiversity-rich ecosystems in the world's oceans. Coral establishes complex interactions with various microorganisms that constitute an important part of the coral holobiont. The best-known coral endosymbionts are Symbiodiniaceae dinoflagellates. Each member of the coral microbiome contributes to its total lipidome, which integrates many molecular species. The present study summarizes available information on the molecular species of the plasma membrane lipids of the coral host and its dinoflagellates (phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine (PS), phosphatidylinositol (PI), ceramideaminoethylphosphonate, and diacylglyceryl-3-O-carboxyhydroxymethylcholine), and the thylakoid membrane lipids of dinoflagellates (phosphatidylglycerol (PG) and glycolipids). Alkyl chains of PC and PE molecular species differ between tropical and cold-water coral species, and features of their acyl chains depend on the coral's taxonomic position. PS and PI structural features are associated with the presence of an exoskeleton in the corals. The dinoflagellate thermosensitivity affects the profiles of PG and glycolipid molecular species, which can be modified by the coral host. Coral microbiome members, such as bacteria and fungi, can also be the source of the alkyl and acyl chains of coral membrane lipids. The lipidomics approach, providing broader and more detailed information about coral lipid composition, opens up new opportunities in the study of biochemistry and ecology of corals.

The Phospholipid Molecular Species Profile of Apostichopus japonicus Tissues Modifies through Exposure to n-3 Polyunsaturated Fatty Acid-Deficient Diet.

The sea cucumber Apostichopus japonicus, being a target species of commercial fisheries and aquaculture, is also used as a source of biologically active compounds with high pharmacological potential. By the methods of high-performance liquid chromatography with high resolution mass spectrometry, we analyzed the major structural phospholipids (PL)-glycerophosphoethanolamines (PE), glycerophosphocholines (PC), glycerophosphoserines (PS), and glycerophosphoinositols (PI)-in tissues of wild and cultured sea cucumbers. The intestines of the wild and cultured animals differed from the other tissues by an elevated content of molecular species of PE, PC, and PS with 22:6n-3 fatty acid. The respiratory trees of the studied animals contained a high level of odd-chain PI and PI with 20:4n-6. The exposure to n-3 PUFA-deficient diet resulted in substantial changes in the molecular species profile of PL of the wild and cultured animals. The cultured sea cucumbers showed a significant decrease in the 20:5n-3 content in all four studied PL classes. A replacement of 20:5n-3 by 20:4n-6 occurred in PE, PC, and PI. The decrease in the level of molecular species of PS with 20:5n-3 was compensated by an increase in the level of monounsaturated long-chain PS. The diet of cultured sea cucumbers is a crucial factor for enhancing the nutritional properties of the product obtained from them.

Coral Holobionts Possess Distinct Lipid Profiles That May Be Shaped by Symbiodiniaceae Taxonomy.

Symbiotic relationships are very important for corals. Abiotic stressors cause the acclimatization of cell membranes in symbionts, which possess different membrane acclimatization strategies. Membrane stability is determined by a unique lipid composition and, thus, the profile of thylakoid lipids can depend on coral symbiont species. We have analyzed and compared thylakoid lipidomes (mono- and digalactosyldiacylglycerols (MGDG and DGDG), sulfoquinovosyldiacylglycerols (SQDG), and phosphatidylglycerols (PG)) of crude extracts from symbiotic reef-building coral Acropora sp., the hydrocoral Millepora platyphylla, and the octocoral Sinularia flexibilis. S. flexibilis crude extracts were characterized by a very high SQDG/PG ratio, a DGDG/MGDG ratio < 1, a lower degree of galactolipid unsaturation, a higher content of SQDG with polyunsaturated fatty acids, and a thinner thylakoid membrane which may be explained by the presence of thermosensitive dinoflagellates Cladocopium C3. In contrast, crude extracts of M. platyphylla and Acropora sp. exhibited the lipidome features of thermotolerant Symbiodiniaceae. M. platyphylla and Acropora sp. colonies contained Cladocopium C3u and Cladocopium C71/C71a symbionts, respectively, and their lipidome profiles showed features that indicate thermotolerance. We suggest that an association with symbionts that exhibit the thermotolerant thylakoid lipidome features, combined with a high Symbiodiniaceae diversity, may facilitate further acclimatization/adaptation of M. platyphylla and Acropora sp. holobionts in the South China Sea.

Physiological processes and lipidome dynamics in the soft coral Sinularia heterospiculata under experimental bleaching.

Coral polyps host intracellular symbiotic dinoflagellates (SD). The loss of SD (referred as bleaching) under stressful environmental conditions is the main reason of coral reef destruction, and therefore, intensively studied over the world. Lipids are the structural base of biomembranes and energy reserve of corals and are directly involved in the coral bleaching. In order to establish a relationship between coral tissue morphology, physiological processes and lipidome dynamics during bleaching, the soft coral Sinularia heterospiculata was exposed to experimental heat stress (33 °C) for 72 h. A chlorophyll content, structure of cells, the level of reactive oxygen species (ROS), and molecular species of storage and structural lipids were analyzed. After 24 h of heat exposure, the level of ROS-positive SD cells did not increase, but the host tissues lost a significant part of SD. The removal of SD cells by exocytosis were suggested. Exocytosis was presumed to prevail at earlier stages of the soft coral bleaching. Symbiophagosomes with degenerative SD were observed in the stressed coral host cells. After 24 h, the content of phosphatidylinositols, which involved in apoptosis and autophagy, was significantly decreased. The innate immune response was triggered, and SD were digested by the coral host. After 48 h, a degradation of SD chloroplasts and a decrease in the specific monogalactosyldiacylglycerol molecular species were detected that confirmed a disruption of lipid biosynthesis in chloroplasts. At the end of coral bleaching, the appearance of oxidized phosphatidylethanolamines, indicating damage to the host membranes, and the degradation of the coral tissues were simultaneously observed. Thus, a switch between dominant mechanisms of the SD loss during bleaching of S. heterospiculata was found and proved by certain variations of the lipidomic profile. Lipidomic parameters may become indicators of physiological processes occurring in the symbiotic coral organism and may be used for assessing anthropogenic or natural destructive effects on coral reefs.

Lipidomes of phylogenetically different symbiotic dinoflagellates of corals.

The structural base of all membranes of symbiotic dinoflagellates (SD) is composed of glycolipids and betaine lipids, whereas triacylglycerols (TG) constitute an energy reserve and are involved in biosynthesis of glycolipids. Since data on the SD lipidome and the host's influence on symbionts' lipidome are scanty, we analyzed and compared the lipidomes of SD isolated from the zoantharian Palythoa tuberculosa and the alcyonarian Sinularia heterospiculata. A sequencing of nuclear gene regions showed that both cnidarians hosted the dinoflagellates Cladocopium sp. (subclades C1 and C3), but the zoantharian also contained the dinoflagellates Durusdinium trenchii (clade D). The presence of the thermotolerant D. trenchii resulted in a higher unsaturation of mono- and digalactosyldiacylglycerols (MGDG and DGDG), but a lower unsaturation of sulfoquinovosyldiacylglycerol (SQDG). The same features were earlier described for same SD from a reef-building coral. Hence, the profile of glycolipid molecules, which form SD thylakoid membranes, seems to be species-specific and does not depend on the host's taxonomic position. In contrast, the betaine lipid molecular species profile of diacylglyceryl-3-O-carboxyhydroxymethylcholine (DGCC), which forms SD cell membranes, can be influenced by the host. The profiles of the TG molecular species from freshly isolated SD have been determined for the first time. These molecular species can be divided on the basis of the acyl group in sn-2 position. The TG with 16:0 acyl group in sn-2 position may enrich total TG of a cnidarian colony and originate from SD cytoplasm. In contrast, TG 18:3/18:4/18:3 may be biosynthetically related with DGDG and concentrated in SD plastoglobules. Our data may be useful for further investigations of natural and technogenic variations in microalgal lipids and symbiont-host interactions in marine ecosystems.

Chemical Diversity of Soft Coral Steroids and Their Pharmacological Activities.

The review is devoted to the chemical diversity of steroids produced by soft corals and their determined and potential activities. There are about 200 steroids that belong to different types of steroids such as secosteroids, spirosteroids, epoxy- and peroxy-steroids, steroid glycosides, halogenated steroids, polyoxygenated steroids and steroids containing sulfur or nitrogen heteroatoms. Of greatest interest is the pharmacological activity of these steroids. More than 40 steroids exhibit antitumor and related activity with a confidence level of over 90 percent. A group of 32 steroids shows anti-hypercholesterolemic activity with over 90 percent confidence. Ten steroids exhibit anti-inflammatory activity and 20 steroids can be classified as respiratory analeptic drugs. Several steroids exhibit rather rare and very specific activities. Steroids exhibit anti-osteoporotic properties and can be used to treat osteoporosis, as well as have strong anti-eczemic and anti-psoriatic properties and antispasmodic properties. Thus, this review is probably the first and exclusive to present the known as well as the potential pharmacological activities of 200 marine steroids.