cis-4,7,10,trans-13–22∶4 fatty acid distribution in phospholipids of pectinid species Aequipecten opercularis and Pecten maximus

Specific regulations of gill membrane fatty acids in response to environmental variability reveal fitness differences between two suspension-feeding bivalves (Nodipecten subnodosus and Spondylus crassisquama)

Bivalves' physiological functions (i.e. growth, reproduction) are influenced by environmental variability that can be concomitant with trophic resource variations in terms of quality and quantity. Among the essential molecules that bivalves need to acquire from their diet to maintain physiological functions, fatty acids (FAs) such as polyunsaturated fatty acids (e.g. 20:4n-6 (arachidonic acid), 20:5n-3 (eicosapentaenoic acid) and 22:6n-3 (docosahexaenoic acid)) have been described to play a critical role. The present study examined the FA composition of gill membrane lipids of two bivalve species, Nodipecten subnodosus and Spondylus crassisquama, sampled in a coastal lagoon of the Northeastern Pacific (Ojo de Liebre, Mexico), at two contrasting locations (inner versus outer part of the lagoon) and at two different periods (February and August 2016). Spatiotemporal variations showed that FA composition of gill membrane lipids was highly correlated to FA composition of reserve lipids from digestive gland. This highlights the marked impact of the diet on FA composition of gill membranes. Interestingly, both species presented differences in the seasonal accumulations of plasmalogens and of particular FA that are not found in their diet (e.g. non-methylene interrupted FA, 22:4n-9trans, 20:1n-11), suggesting specific regulations of FA incorporation and lipid class composition in gill membranes to maintain optimal membrane function in their specific and changing environment. This study highlights the importance to characterize the spatial and temporal variability of food resources in order to apprehend the physiological consequences of environmental variability, as well as species differential regulation capacities in a changing world.

Altered membrane lipid composition and functional parameters of circulating cells in cockles (Cerastoderma edule) affected by disseminated neoplasia

Membrane lipid composition and morpho-functional parameters were investigated in circulating cells of the edible cockle (Cerastoderma edule) affected by disseminated neoplasia (neoplastic cells) and compared to those from healthy cockles (hemocytes). Membrane sterol levels, phospholipid (PL) class and subclass proportions and their respective fatty acid (FA) compositions were determined. Morpho-functional parameters were evaluated through total hemocyte count (THC), mortality rate, phagocytosis ability and reactive oxygen species (ROS) production. Both morpho-functional parameters and lipid composition were profoundly affected in neoplastic cells. These dedifferentiated cells displayed higher THC (5×), mortality rate (3×) and ROS production with addition of carbonyl cyanide m-chloro phenylhydrazone (1.7×) but lower phagocytosis ability (½×), than unaffected hemocytes. Total PL amounts were higher in neoplastic cells than in hemocytes (12.3 and 5.1 nmol×10(-6) cells, respectively). However, sterols and a particular subclass of PL (plasmalogens; 1-alkenyl-2-acyl PL) were present in similar amounts in both cell type membranes. This led to a two times lower proportion of these membrane lipid constituents in neoplastic cells when compared to hemocytes (20.5% vs. 42.1% of sterols in total membrane lipids and 21.7% vs. 44.2% of plasmalogens among total PL, respectively). Proportions of non-methylene interrupted FA- and 20:1n-11-plasmalogen molecular species were the most impacted in neoplastic cells when compared to hemocytes (⅓× and ¼×, respectively). These changes in response to this leukemia-like disease in bivalves highlight the specific imbalance of plasmalogens and sterols in neoplastic cells, in comparison to the greater stability of other membrane lipid components.

Occurrence of the cis-4,7,10, trans-13-22:4 fatty acid in the family Pectinidae (Mollusca: Bivalvia)

The present study aimed to elucidate the effective phylogenetic specificity of distribution of a cis-4,7,10, trans-13-22:4 (22:4(n-9)Delta13trans) among pectinids. For this purpose, we extended the analysis of membrane glycerophospholipids FA composition to 13 species of scallops, covering 11 genera and 7 tribes representatives of the three subfamilies Chlamydinae, Palliolinae and Pectininae and the subgroup Aequipecten. In species belonging to the subfamily Pectininae and the Aequipecten subgroup, 22:4(n-9)Delta13trans was found in substantial amounts, but it was absent in other species belonging to the subfamilies Chlamydinae and Palliolinae. Homologous non-methylene-interrupted (NMI) FA, also hypothesized to differ along phylogenetic lines in bivalves, were totally absent or present only in trace amounts in representatives of the Aequipecten subgroup but ranged from 0.3 to 4.5% of the total FA in Pectinidae, Chlamydinae, and Palliolinae subfamilies. The species-specific occurrence of NMI and 22:4(n-9)Delta13trans FA in membrane lipids of pectinids agrees with the most recent phylogenies based on shell morphology and molecular characteristics. We examined the potential timing of the appearance of 22:4(n-9)Delta13trans in pectinids on a geologic time scale.

Non-methylene-interrupted fatty acids from marine invertebrates: Occurrence, characterization and biological properties

Marine organisms, in particular invertebrates, have proved to be a major source of unique fatty acid (FA) structures originating from unusual biosynthetic pathways. Among them, non-methylene-interrupted (NMI) FA occur in various molluscs in the wide ranges of concentrations (up to 20%), such as the most often encountered 20:2 Delta5,11, 20:2 Delta5,13, 22:2 Delta7,13 or 22:2 Delta7,15. Such NMI FA have also been reported from algae, echinoderms, sponges, tropical rays, and many other invertebrates. The most intriguing marine invertebrates seem to be sponges that commonly contain very long-chain Delta5,9 FA. A third double bond can occur in the NMI FA as reported in some marine organisms, such as 20:3 Delta7,13,16 or 30:3 Delta5,9,23. Lipids of invertebrates from deep-sea hydrothermal and cold-seep vents gave rise to an intense research activity including reports on unprecedented NMI polyunsaturated FA. The bivalve molluscs are able to synthesize de novo the NMI FA but their precise biological interest is presently not well-known, although structural and functional roles in biological membranes have been suggested, in particular a higher resistance to oxidative processes and microbial lipases. Biosynthetic pathways of Delta5,9 FA in sponges were demonstrated up to C(26) FA structures and include particular elongation and desaturation steps. Recently, intense research effort has been conducted to investigate the biomedical potential of these unusual FA. Thus, Delta5,9 FA displayed interesting antiplasmodial activity. The most promising FA topoisomerase I inhibitors to date seem to be the long-chain Delta5,9 FA. This inhibitory activity is probably partially responsible for the toxicity displayed by some of the Delta5,9 FA towards cancer cell lines.