Fatty acid composition of polar lipid classes during larval development of scallop Pecten maximus (L.)

A Diet Rich in HUFAs Enhances the Energetic and Immune Response Capacities of Larvae of the Scallop Argopecten purpuratus

Massive mortalities in farmed larvae of the scallop Argopecten purpuratus have been associated with pathogenic Vibrio outbreaks. An energetic trade-off between development-associated demands and immune capacity has been observed. Given that highly unsaturated fatty acids (HUFAs) are essential nutrients for larval development, we evaluated the effect of diets based on microalgae low and high in HUFAs (LH and HH, respectively) on the energetic condition and the immune response of scallop larvae. The results showed that the HH diet increased cellular membrane fluidity in veliger larvae. The routine respiration rate was 64% higher in the HH-fed veligers than in the LH-fed veligers. Additionally, the metabolic capacity tended to be higher in the HH-fed veligers than in the LH-fed veligers after the Vibrio challenge. After the challenge, the HH-fed veligers presented higher transcript induction of ApTLR (immune receptor) and ApGlys (immune effector) genes, and the HH-fed pediveligers presented higher induction of ApLBP/BPI1 (antimicrobial immune effector) gene, than the LH-fed larvae. Furthermore, the HH-fed veligers controlled total Vibrio proliferation (maintaining near basal levels) after the bacterial challenge, while the LH-fed veligers were not able to control this proliferation, which increased three-fold. Finally, the HH-fed larvae showed 20-25% higher growth and survival rates than the LH-fed veligers. Overall, the results indicated that the administration of a HH diet increases cell membrane fluidity and energy metabolic capacity, which in turn enhances immunity and the ability to control Vibrio proliferation. The administration of microalgae high in HUFAs would be a promising strategy for improving scallop larval production efficiency.

Linking ecology, morphology, and metabolism: Niche differentiation in sympatric populations of closely related species of the genus Littorina (Neritrema)

Divergence of ecological niches in phylogenetically closely related species indicates the importance of ecology in speciation, especially for sympatric species are considered. Such ecological diversification provides an advantage of alleviating interspecies competition and promotes more efficient exploitation of environmental resources, thus being a basis for ecological speciation. We analyzed a group of closely related species from the subgenus Neritrema (genus Littorina, Caenogastropoda) from the gravel-bouldery shores. In two distant sites at the Barents and Norwegian Sea, we examined the patterns of snail distribution during low tide (quantitative sampling stratified by intertidal level, presence of macrophytes, macrophyte species, and position on them), shell shape and its variability (geometric morphometrics), and metabolic characteristics (metabolomic profiling). The studied species diversified microbiotopes, which imply an important role of ecological specification in the recent evolution of this group. The only exception to this trend was the species pair L. arcana / L. saxatilis, which is specifically discussed. The ecological divergence was accompanied by differences in shell shape and metabolomic characteristics. Significant differences were found between L. obtusata versus L. fabalis and L. saxatilis / L. arcana versus L. compressa both in shell morphology and in metabolomes. L. saxatilis demonstrated a clear variability depending on intertidal level which corresponds to a shift in conditions within the occupied microhabitat. Interestingly, the differences between L. arcana (inhabiting the upper intertidal level) and L. compressa (inhabiting the lower one) were analogous to those between the upper and lower fractions of L. saxatilis. No significant level-dependent changes were found between the upper and lower fractions of L. obtusata, most probably due to habitat amelioration by fucoid macroalgae. All these results are discussed in the contexts of the role of ecology in speciation, ecological niche dynamics and conservatism, and evolutionary history of the Neritrema species.

Evolved differences in energy metabolism and growth dictate the impacts of ocean acidification on abalone aquaculture

The pH of the global ocean is decreasing due to the absorption of anthropogenically emitted CO₂, causing ocean acidification (OA). OA negatively impacts marine shellfish and threatens the continuing economic viability of molluscan shellfish aquaculture, a global industry valued at more than 19 billion USD. We identify traits linked to growth and lipid regulation that contribute tolerance to OA in abalone aquaculture, with broader implications for adaptation efforts in other shellfish species. We also identify evolved heritable variation for physiological resilience to OA that may be exploited in commercial and restoration aquaculture breeding programs to offset the negative consequences of continuing climate change.

Ocean acidification (OA) poses a major threat to marine ecosystems and shellfish aquaculture. A promising mitigation strategy is the identification and breeding of shellfish varieties exhibiting resilience to acidification stress. We experimentally compared the effects of OA on two populations of red abalone (Haliotis rufescens), a marine mollusc important to fisheries and global aquaculture. Results from our experiments simulating captive aquaculture conditions demonstrated that abalone sourced from a strong upwelling region were tolerant of ongoing OA, whereas a captive-raised population sourced from a region of weaker upwelling exhibited significant mortality and vulnerability to OA. This difference was linked to population-specific variation in the maternal provisioning of lipids to offspring, with a positive correlation between lipid concentrations and survival under OA. This relationship also persisted in experiments on second-generation animals, and larval lipid consumption rates varied among paternal crosses, which is consistent with the presence of genetic variation for physiological traits relevant for OA survival. Across experimental trials, growth rates differed among family lineages, and the highest mortality under OA occurred in the fastest growing crosses. Identifying traits that convey resilience to OA is critical to the continued success of abalone and other shellfish production, and these mitigation efforts should be incorporated into breeding programs for commercial and restoration aquaculture.

An integrated omics approach to investigate summer mortality of New Zealand Greenshell™ mussels

BACKGROUND

Green-lipped mussels, commercially known as Greenshell™ mussels (Perna canaliculus Gmelin 1791), contribute > $300 million to New Zealand's aquaculture exports. However, mortalities during summer months and potential pathogenic outbreaks threaten the industry. Thermal stress mechanisms and immunological responses to pathogen infections need to be understood to develop health assessment strategies and early warning systems.

METHODS

P. canaliculus were collected during a mortality event at a commercial aquaculture farm in Firth of Thames, New Zealand. Gill tissues from six healthy and six unhealthy mussels were excised and processed for metabolomic (GC-MS) and label-free proteomic (LC-MS) profiling. Univariate analyses were conducted separately on each data layer, with data being integrated via sparse multiple discriminative canonical correlation analysis. Pathway enrichment analysis was used to probe coordinated changes in functionally related metabolite sets.

RESULTS

Findings revealed disruptions of the tricarboxylic acid (TCA) cycle and fatty acid metabolism in unhealthy mussels. Metabolomics analyses also indicated oxidative stress in unhealthy mussels. Proteomics analyses identified under-expression of proteins associated with cytoskeleton structure and regulation of cilia/flagellum in gill tissues of unhealthy mussels. Integrated omics revealed a positive correlation between Annexin A4 and CCDC 150 and saturated fatty acids, as well as a negative correlation between 2-aminoadipic acid and multiple cytoskeletal proteins.

CONCLUSIONS

Our study demonstrates the ability of using integrative omics to reveal metabolic perturbations and protein structural changes in the gill tissues of stressed P. canaliculus and provides new insight into metabolite and protein interactions associated with incidences of summer mortality in this species.

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.

Characterization of glycerophospholipid molecular species in muscles from three species of cephalopods by direct infusion-tandem mass spectrometry

More than 200 molecular species of glycerophospholipids (GP) including glycerophosphocholine (GPC), glycerophosphoethanolamine (GPE), glycerophosphoserine (GPS), lysoglycerophosphocholine (LGPC), lysoglycerophosphoethanolamine (LGPE) and lysoglycerophosphoserine (LGPS), as well as 18 kinds of sphingomyelin (SM) were characterized by using a direct infusion-tandem mass (MS/MS) spectrometry method for lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis for the first time. The majority of the GP molecular species contained long-chain omega-3 polyunsaturated fatty acids (n-3 LC-PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Therefore, cephalopods can be a good possible source of dietary GP carrying n-3 LC-PUFA. The total lipids were composed of phospholipid (PL, 72.29-83.32 wt% of total lipids), cholesterol (12.70-23.60 wt% of total lipids), triacylglycerol (1.86-2.93 wt% of total lipids), diacylglycerol (0.15-1.09 wt% of total lipids), monoacylglycerol (0.06-0.18 wt% of total lipids) and free fatty acid (0.72-1.86 wt% of total lipids). For PL, phosphatidylcholine (44.47-62.30 mol%), phosphatidylethanolamine (22.57-39.08 mol%), phosphatidylserine (6.15-10.18 mol%), phosphatidylglycerol (0.68-3.11 mol%), phosphatidylinositol (2.41-7.15 mol%) and lysophosphatidylcholine (1.84-5.24 mol%) were detected. Furthermore, the total lipids from the muscles of cephalopods Sepiella maindroni, Octopus ocellatus and Loligo chinensis contained 41.80-50.02 mol% of saturated fatty acids, 11.53-21.54 mol% of monounsaturated fatty acids and 36.67-40.82 mol% of PUFA, whilst DHA (15.25-26.71 mol%) and EPA (6.29-16.57 mol%) were found to account for the majority of the PUFA. With these data presented, cephalopod muscle can be considered as a healthy food for humans.

Lipidomic Analysis: From Archaea to Mammals

Lipids are among the most important organic compounds found in all living cells, from primitive archaebacteria to flowering plants or mammalian cells. They form part of cell walls and constitute cell storage material. Their biosynthesis and metabolism play key roles in faraway topics such as biofuel production (third-generation biofuels produced by microorganisms, e.g. algae) and human diseases such as adrenoleukodystrophy, Zellweger syndrome, or Refsum disease. Current lipidomic analysis requires fast and accurate processing of samples and especially their characterization. Because the number of possible lipids and, more specifically, molecular species of lipids is of the order of hundreds to thousands, it is necessary to process huge amounts of data in a short time. There are two basic approaches to lipidomic analysis: shotgun and liquid chromatography-mass spectometry. Both methods have their pros and cons. This review deals with lipidomics not according to the type of ionization or the lipid classes analyzed but according to the types of samples (organisms) under study. Thus, it is divided into lipidomic analysis of archaebacteria, bacteria, yeast, fungi, algae, plants, and animals.

Validation of trophic and anthropic underwater noise as settlement trigger in blue mussels

Like the majority of benthic invertebrates, the blue mussel Mytilus edulis has a bentho-pelagic cycle with its larval settlement being a complex phenomenon involving numerous factors. Among these factors, underwater noise and pelagic trophic conditions have been weakly studied in previous researches. Under laboratory conditions, we tested the hypothesis that picoplankton assimilation by the pediveliger blue mussel larvae acts as a food cue that interacts with anthropic underwater sound to stimulate settlement. We used ¹³C-labeling microalgae to validate the assimilation of different picoplankton species in the tissues of pediveliger larvae. Our results clearly confirm our hypothesis with a significant synergic effect of these two factors. However, only the picoeukaryotes strains assimilated by larvae stimulated the settlement, whereas the non-ingested picocyanobacteria did not. Similar positive responses were observed with underwater sound characterized by low frequency vessel noises. The combination of both factors (trophic and vessel noise) drastically increased the mussel settlement by an order of 4 compared to the control (without picoplankton and noise). Settlement levels ranged from 16.5 to 67% in 67 h.

Effect of biofilm age on settlement of Mytilus edulis

Biofilm ageing is commonly assumed to improve mussel settlement on artificial substrata, but the structure and taxonomic composition of biofilms remains unclear. In the present study, multi-species biofilms were characterized at different ages (1, 2, and 3 weeks) and their influence on settlement of the blue mussel, Mytilus edulis, was tested in the field. As biofilms can constitute a consistent food resource for larvae, the lipid quality, defined as the proportion of related essential fatty acids, may be a selection criterion for settlement. Overall mussel settlement increased on biofilms older than 1 week, and the enhanced settlement corresponded to the abundance and composition of the biofilm community, rather than to essential fatty acid levels. However, during a pulse of phytoplankton, the positive influence of biofilm was not detected, suggesting that pelagic cues overwhelmed those associated with biofilms. The influence of biofilms on mussel settlement could be more crucial when planktonic resources are limited.

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.

A striking parallel between cardiolipin fatty acid composition and phylogenetic belonging in marine bivalves: a possible adaptative evolution?

Thirty-five species of marine mollusk bivalves were analyzed for their fatty acid (FA) composition of cardiolipin (Ptd(2)Gro). All species showed a Ptd(2)Gro with strong selectivity for only a few polyunsaturated fatty acids, but three characteristic FA profiles emerged, with clear parallels to bivalve phylogeny. A first group of 12 species belonging to the Eupteriomorphia subgroup (Filibranchia) was characterized by a Ptd(2)Gro almost exclusively composed of 22:6n-3, whereas in the four Filibranchia Pteriomorph species analyzed, this FA was combined with substantial proportions of 18:2n-6 and 18:3n-3. Finally, a third group of 20 species, all belonging to the Heterodonta subclass, possessed Ptd(2)Gro containing predominantly both 22:6n-3 and 20:5n-3. Polyunsaturated FA moieties and arrangements in the Ptd(2)Gro of some marine species investigated in other classes of the mollusk phylum (Gastropoda, Polyplacophora) were found to be different. The present results suggest that the specific Ptd(2)Gro FA compositions in bivalves are likely to be controlled and conserved in species of the same phylogenetic group. Functional significances of the evolution of this mitochondrial lipid structure in bivalves are discussed.

Comparison of three solid-phase extraction methods for fatty acid analysis of lipid fractions in tissues of marine bivalves

Objective of this study was to investigate the effect of using pre-packed Si (Si), manually packed silica hydrated with water (Si-H(2)O) and pre-packed aminopropyl-bonded silica (NH(2)), at various mass ratios of lipid to sorbent, on the recovery of polar lipids following the solid-phase extraction (SPE) of a standard mixture of lipids. We also applied SPE using these sorbents to the separation of lipids from oyster tissues and compared the fatty acid (FA) composition of each fraction. Recoveries of phospholipids after SPE using Si increased with an increasing ratio of lipid to sorbent. Although the use of Si-H(2)O improved the recovery of polar lipid compared to that obtained on Si, the neutral lipid from gills and muscles of oyster showed distorted FA compositions presumably due to a leakage of polar lipids. Finally, NH(2) eluted with methanol provided good recoveries of phospholipids from the standard mixture; although polar lipids of oyster tissues showed a reduction in 20:4n-6 and MUFA likely due to the selective retention of acidic phospholipids.

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

The distribution of cis-4,7,10,trans-13-docosatetraenoic (c4,7,10,t13-22:4), a peculiar FA previously isolated in the glycerophospholipids of some pectinid bivalves, was investigated in glycerophospholipid classes and subclasses of separated organs (gills, mantle, gonads, and muscle) of the queen scallop Aequipecten opercularis and the king scallop Pecten maximus. Plasmalogen (Pls) and diacyl + alkyl (Ptd) forms of serine, ethanolamine, and choline glycerophospholipids were isolated by HPLC and their FA compositions analyzed by GC-FID. PIs and Ptd forms of serine glycerophospholipids (PlsSer and PtdSer), and to a lesser extend the Pls form of ethanolamine glycerophospholipids (PlsEtn), were found to be specifically enriched with c4,7,10,t13-22:4. This specificity was found to decrease in the tested organs in the following order: gills, mantle, gonad, and muscle. In gills, c4,7,10,t13-22:4 was shown to be the main unsaturated FA of serine glycerophospholipids in both Pls and Ptd forms (23.8 and 19.4 mol%, respectively, for A. opercularis, and 21.0 and 26.2 mol% for P. maximus). These results represent the first comprehensive report on the FA composition of plasmalogen serine subclass isolated from pectinid bivalves. The specific association of the PlsSer with the c4,7,10,t13-22:4 for the two pectinid species can be paralleled to the specific association of the PlsSer with the non-methylene interrupted (NMI) FA and 20:1 (n-11) observed in mussels, clams, and oysters (Kraffe, E., Soudant, P., and Marty, Y. (2004) Fatty Acids of Serine, Ethanolamine and Choline Plasmalogens in Some Marine Bivalves, Lipids 39, 59-66.) This, led us to hypothesize a similar functional significance for c4,7,10,t13-22:4, NMI FA, and 20:1 (n-11) associated with PlsSer subclass of bivalves.

Docosahexaenoic acid- and eicosapentaenoic acid-enriched cardiolipin in the Manila clam Ruditapes philippinarum

The FA composition of cardiolipin (CL) from the Manila clam Ruditapes philippinarum was investigated in whole body and individual organs. CL was isolated by HPLC and its chemical structure characterized using NMR spectroscopy. Two prominent FA, EPA and DHA, were found in approximately equal proportions, contributing together up to 73 mol% of the total FA. The FA composition of CL is presumed to reflect a specific synthesis pathway independent of diet and of total glycerophospholipid FA composition. To the best of our knowledge, this is the first time that a CL dominated by the two PUFA 22:6n-3 and 20:5n-3 has been characterized and described. This EPA + DHA specificity of the CL in the Manila clam is thought to reflect a functional and structural modification of mitochondrial membranes of this bivalve species compared with scallops, oysters, and mussels that possess a CL dominated by DHA. The FA composition and levels of CL differed little between separated organs, and the large pool of DHA and EPA was found fairly equally distributed in gills, mantle, foot, siphon, and muscle. However, whereas DHA and PUFA levels were most stable between organs, EPA and arachidonic acid were significantly more variable and seemed to be interrelated.

Techniques for delivery of arachidonic acid to pacific oyster, Crassostrea gigas, spat

The present study tested two techniques for dietary supplementation of Crassostrea gigas spat with PUFA, such as arachidonic acid (AA). The first technique consisted of a preliminary enrichment and growth of an algal concentrate (T-ISO, Isochrysis sp.) with AA dissolved in an ethanol solution, the whole culture then being fed to the spat. This enrichment increased the AA weight percentage in T-ISO neutral and polar lipids from 0.6 to 22.4% and from 0.4 to 6.8%, respectively. The second delivery technique was direct addition separately of free AA dissolved in ethanol solution and algal concentrate (T-ISO + AA) to the spat-rearing tank. To test the efficiency of these delivery techniques, oyster spat were supplemented with AA-enriched T-ISO, T-ISO + AA, and T-ISO alone. The possible biological impacts of these dietary treatments were assessed by measuring growth, condition index, and TAG content of oyster spat. Dry weight and condition index of spat fed AA-enriched T-ISO decreased by 24 and 49%, respectively, after 26 d of feeding; basically, TAG content declined 88% after 34 d of conditioning. When AA was added directly to seawater, spat growth and condition index were comparable with those of oysters fed T-ISO alone. AA incorporation in oyster tissues was assessed by analysis of the FA compositions in both neutral and polar lipid fractions. After 34 d, AA content in neutral lipids reached 7 and 11.7% in the spat fed, respectively, AA-enriched T-ISO and T-ISO + AA, as compared with 1.1% in spat fed only T-ISO. AA incorporation was greater in polar lipids than in neutral lipids, reaching 7.8 and 12.5% in spat fed AA-enriched T-ISO and T-ISO + AA, respectively. A direct addition of PUFA along with the food supply represents an effective and promising means to supplement PUFA to oyster spat.

Incorporation and modification of dietary fatty acids in gill polar lipids by two bivalve species Crassostrea gigas and Ruditapes philippinarum

Two bivalve species Crassostrea gigas and Ruditapes philippinarum were fed eight weeks with three mono-specific algae diets: T-Isochrysis galbana, Tetraselmis suecica, Chaetoceros calcitrans, selected on the basis of their polyunsaturated fatty acid (PUFA) composition. The incorporation and the modification of dietary fatty acids in C. gigas and R. philippinarum gill lipids were analysed and compared. Essential PUFA (20:4n-6, 20:5n-3 and 22:6n-3) and non-methylene interrupted PUFAs (known to be synthesised from monounsaturated precursors) contents of gill polar lipid of both species were greatly influenced by the dietary conditioning. Interestingly, oysters and clams responded differentially to the mono-specific diets. Oysters maintained higher 20:5n-3 level and higher 22:2j/22:i and n-7/n-9 ratio in gill polar lipids than clams. To better discriminate dietary and species influences on the fatty acid composition, a Principal Component Analysis followed by a MANOVA on the two most explicative components was performed. These statistical analyses showed that difference in fatty acid compositions attributable to species were just as significant as the diet inputs. The differences of gill fatty acid compositions between oysters and clams are speculated to result of an intrinsic species characteristic and perhaps of a group characteristic: Fillibranch vs. Eulamellibranch.

Lipid and FA composition of the pearl oyster Pinctada fucata martensii: Influence of season and maturation

The lipid and FA composition of the total lipids of the pearl oyster Pinctada fucata martensii, in different seasons and in different areas, were analyzed to clarify its lipid physiology and to estimate the possible influence of its prey phytoplankton. During the spawning season (June and July), the lipid contents were slightly higher than in the growing season (November and March). TAG and sterols were the major components in the neutral lipids in all conditions, whereas high levels of phospholipids (PE and PC) were found in the polar lipids. In addition, significant levels of ceramide aminoethyl phosphonate but low levels of sphingolipids were found in the polar lipids. The major FA in the TAG in all samples were 14:0, 16:0, and 18:0 as saturated FA (saturates); 16:1 n-7, 18:1 n-9, and 18:1 n-7 as monoenoic FA (monoenes); and 20:4n-6 (arachidonic acid: AA), 20:5n-3 (EPA), and 22:6n-3 (DHA) as PUFA. The major components found in the polar lipids were 16:0 and 18:0 as saturates; 22:2n-9,15 and 22:2n-7,15 as non-methylene-interrupted dienes (NMID), and AA, 22:3n-6,9,15, EPA, and DHA as PUFA. Similar to the high levels of total PUFA in the phospholipids, comparatively high PUFA levels were found in TAG in both the growing and the spawning season. This may be a characteristic of the species as a typical bivalve, because the lipids were similar to those of other bivalves. Although it is a marine animal, uncharacteristically high levels of AA were found in both the TAG and phospholipids. This result suggests that lipids of P. fucata may be influenced by those of its phytoplanktonic prey. The increase in levels of NMID from TAG to PE with a decrease in those of monoenes suggests that the tissues of this species are able to biosynthesize only the less unsaturated PUFA, such as NMID. In particular, NMID derivatives are considered to be biosynthesized in the PE; thus, they might play a particular role in the membrane, because NMID were characteristically localized only in the PE.

Fatty acids of serine, ethanolamine, and choline plasmalogens in some marine bivalves

The FA composition of glycerophospholipid (GPL) classes and subclasses was investigated in whole animals of three marine bivalve mollusks: the Japanese oyster Crassostrea gigas, the blue mussel Mytilus edulis, and the Manila clam Ruditapes philippinarum. Individual organs (gills, mantle, foot, siphon, and muscle) of the Manila clam also were examined. The PS plasmalogen (PSplsm), PE plasmalogen (PEplsm), and PC plasmalogen (PCplsm) subclasses were isolated by HPLC, and their individual FA compositions were examined using GC. Plasmalogen forms of PS and PE, when compared to their respective diacyl forms, were found to be specifically enriched with non-methylene-interrupted (NMI) FA (7,15-22:2, 7,13-22:2, and their precursors) and 20:1 n-11 FA. Such a clear specific association was not found for PCplsm. Interestingly, this trend was most apparent in PSplsm, and the above FA were found to be, respectively, the predominant PUFA and monounsaturated FA in the PSplsm isolated from the three species. This specificity was maintained in all the analyzed organs of the Manila clam but varied in proportions: The highest level of plasmalogens, NMI FA, and 20:1 n-11 was measured in gills and the lowest was in muscle. These results represent the first comprehensive report on a FA composition of the PSplsm subclass isolated from mollusks. The fact that NMI FA and 20:1 n-11, which are thought to be biosynthesized FA, were mainly associated with aminophospholipid plasmalogens (PE and PS) is likely to have a functional significance in bivalve membranes.

Effect of a mono-specific algal diet on immune functions in two bivalve species--Crassostrea gigas and Ruditapes philippinarum

The impact of diets upon the fatty acid composition of haemocyte polar lipids and consequently upon immune parameters has been tested in the oyster Crassostrea gigas and the clam Ruditapes philippinarum. Oysters and clams were fed each of three cultured algae: Chaetoceros calcitrans, which is rich in 20:5(n-3) and 20:4(n-6) and poor in 22:6(n-3) fatty acids; T-Iso (Isochrysis sp.), which is rich in 22:6(n-3) and deficient in 20:5(n-3) and 20:4(n-6); and Tetraselmis suecica, which is deficient in 22:6(n-3) and contains only small amounts of 20:5(n-3) and 20:4(n-6). Fatty acid composition of haemocyte polar lipids was greatly affected by the diet. Oysters and clams fed C. calcitrans maintained a higher proportion of 20:5(n-3) and 20:4(n-6) in their haemocyte polar lipids, while these polyunsaturated fatty acids decreased drastically for animals fed T-Iso. However, the T-Iso diet maintained 22:6(n-3) in haemocyte polar lipids of both species. Higher 20:5(n-3) and 20:4(n-6) contents in diets appeared to have a positive effect upon total haemocyte count, granulocyte percentage, phagocytic rate and oxidative activity of clam haemocytes. Similarly, a positive effect of 20:5(n-3) on oxidative activity of oyster haemocytes was observed but to a lesser extent than in clams. Interestingly, when oyster haemocytes are submitted to a stressful condition, a positive effect of a higher dietary 22:6(n-3) content on the phagocytic rate was noticed.

Evidence of a tetradocosahexaenoic cardiolipin in some marine bivalves

Separation of phospholipid classes in lipid extracts from the scallop Pecten maximus, the Pacific oyster Crassostrea gigas, and the blue mussel Mytilus edulis was conducted using HPLC. An isolated polar lipid fraction was found to contain a very high level of DHA, up to 80 mol% of the total FA. MS with electrospray ionization in the positive-ion mode, tandem MS (MS-MS) and multidimensional NMR spectroscopy were used to analyze the detailed chemical structure of this polar lipid fraction. The isolated fraction contained exclusively cardiolipin (CL) molecules, predominantly in a form with four docosahexaenoyl chains (Do4CL). To the best of our knowledge, this is the first time that such a CL form has been analytically characterized and described in these three bivalve species. This tetradocosahexaenoic CL is presumed to reflect a specific adaptation in bivalves that enhances the structural and functional mechanisms of biomembranes in response to variations in environmental conditions (temperature, salinity, emersion).

Detection of plasmalogen from plasma low density lipoprotein and high density lipoprotein in carp, Cyprinus carpio, and rainbow trout, Oncorhynchus mykiss

The study revealed the presence of plasmalogens in the low density lipoprotein (LDL) and high density lipoprotein (HDL) of the fish. The composition of the plasmalogen in the carp plasma LDL phospholipids was 0.94 and 0.23% in the HDL; the LDL phospholipids in the rainbow trout were 0.44% and the HDL was 0.18%. Aldehydes from the plasmalogen were derivatized with dansylhydrazides and separated by high performance liquid chromatography (HPLC). Their presence was detected using a fluorescence detector. Hexadecanal (C16: 0), octadecanal (C18: 0) and octadecenal (C18: 1) were determined to be the major components in the carp and rainbow trout.