The Chilean scallop Argopecten purpuratus (Lamarck, 1819): II. manipulation of the fatty acid composition and lipid content of the eggs via lipid supplementation of the broodstock diet

Lipid droplets play versatile roles in ovarian development of the razor clam Sinonovacula constricta: Insights from proteomic and lipidomic analyses

Lipid droplet (LD) deposition is a common phenomenon during ovarian development across marine mollusks; however, studies on the protein and lipid composition of their ovarian LDs remain limited. Here, we purified LDs from the ovaries of Sinonovacula constricta and isolated proteins and lipids from these purified LDs for proteomic and lipidomic analyses. Our proteomic analysis identified 3243 proteins, with PLIN2 being the most abundant (37.03 ± 13.56 %). We subsequently conducted a functional analysis of the top 500 most abundant LD-associated proteins, categorizing them into 15 groups, including those involved in lipid metabolism, sterol biosynthesis, tricarboxylic acid cycle, carbohydrate metabolism, G protein superfamily, protein chaperones, transport proteins, nucleotide-catabolic process, protein processing and degradation, cytoskeletal proteins, oxidative stress and immunity, and ribosome-associated proteins. In our lipidomic analysis, we identified 1158 molecules across 52 lipid classes, with phosphatidylcholine (PC) exhibiting the greatest diversity at 209 varieties, followed by EtherPC with 177 varieties and triglyceride (TG) with 149 varieties. The fatty acid (FA) analysis of LDs revealed that 16:0 was the most abundant (30.01 ± 0.42 %). Additionally, LDs were found rich in long-chain polyunsaturated FAs (35.63 ± 4.36 %), particularly EPA and DHA. Moreover, we analyzed the FA composition of TGs, PCs, and EtherPCs derived from ovarian LDs. In PCs and TGs, the predominant FAs were 16:0, 16:1, and 18:3, while 16:0, 22:6, and 18:4 constituted the major FA species in EtherPCs. Together, our results suggest that ovarian LDs in S. constricta not only participate in lipid metabolism but also interact with other organelles and metabolic processes, thereby facilitating ovarian development.

Sexual dimorphism in the gonad lipidome of blue mussels (Mytilus sp.): New insights from a global lipidomics approach

Blue mussels (Mytilus sp.) are an economically important species for European aquaculture. Their importance as a food source is expected to increase in the coming net-zero society due to their low environmental footprint; however, their production is affected by anthropogenic stressors and climate change. During reproduction, lipids are key molecules for mussels as they are the main source of energy on which newly hatched embryos depend in the first days of their development. In this work, blue mussels of different origins are analysed, focusing on the differences in lipid composition between the ovary (BMO) and the testis (BMT). The lipidome of blue mussel gonads (BMG) is studied here by combining traditional lipid profiling methods, such as fatty acid and lipid class analysis, with untargeted liquid chromatography-mass spectrometry (LC-MS) lipidomics. The approach used here enabled the identification of 770 lipid molecules from 23 different lipid classes in BMG. BMT, which consists of billions of spermatocytes, had greater amounts of cell membrane and membrane lipid components such as FA18:0, C20 polyunsaturated fatty acids (PUFA), free sterols (ST), ceramide phosphoethanolamines (CerPE), ceramide aminoethylphosphonates (CAEP), cardiolipins (CL), glycerophosphocholines (PC), glycerophosphoethanolamines (PE) and glycerophosphoserines (PS). In BMO, saturated fatty acids (FA14:0 and FA16:0), monounsaturated fatty acids (MUFA) and other storage components such as C18-PUFA accumulated in triradylglycerolipids (TG) and alkyldiacylglycerols (neutral plasmalogens, TG O-), which, together with terpenes, wax esters and cholesterol esters, make up most of oocytes yolk reserves. BMO also had higher levels of ceramides (Cer) and generally alkyl/alkenyl glycerophospholipids (mainly plasmanyl/plasmenyl PC), suggesting a role for these lipids in vitellogenesis. Non-methylene interrupted dienoic fatty acids (NMID FA), typically found in plasmalogens, were the only membrane-forming PUFA predominantly detected in BMO. The results of this study are of great importance for clarifying the lipid composition of BMG and provide an important basis for future studies on the reproductive physiology of these organisms.

Seasonal changes of commercial traits, proximate and fatty acid compositions of the scallop Flexopecten glaber from the Mediterranean Sea (Southern Italy)

This study provides information on biological (gonadosomatic index), commercial quality (condition index and meat yield) and biochemical aspects (proximate composition, fatty acids) of the soft tissues of Flexopecten glaber reared in suspended cages in the Ionian Sea. The results showed that condition index (CI) and meat yield (MY) peaked in December (60 and 30%, respectively) and in April, May and June (from 53 to 60% for CI and from 34 to 36% for MY). Gonadosomatic index showed three main peaks in winter, spring and summer months. Contents of protein 8.18–11.9 g/100 g), lipid (0,.78–1.18 g/100 g) and carbohydrate (1.19–3.30 g/100 g) varied significantly during the study period. Saturated fatty acids was the dominant group, except in December when polyunsaturated fatty acids showed the highest proportion (43% of total FAs). Fatty acids of the n3 group were dominant with docosahexaenoic and eicosapentaenoic acids. Highest n3/n6 ratios were recorded in spring-summer specimens, with values > of 5. The results showed a better nutritional quality of scallops in May, July and December.

Fatty acids from lipids of marine organisms: molecular biodiversity, roles as biomarkers, biologically active compounds, and economical aspects

Because of their characteristic living environments, marine organisms produce a variety of lipids. Fatty acids constitute the essential part of triglycerides and wax esters, which are the major components of fats and oils. Nevertheless, phospholipids and glycolipids have considerable importance and will be taken into account, especially the latter compounds that excite increasing interest regarding their promising biological activities. Thus, in addition to the major polyunsaturated fatty acids (PUFA) such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, a great number of various fatty acids occur in marine organisms, e.g. saturated, mono- and diunsaturated, branched, halogenated, hydroxylated, methoxylated, non-methylene-interrupted. Various unprecedented chemical structures of fatty acids, and lipid-containing fatty acids, have recently been discovered, especially from the most primitive animals such as sponges and gorgonians. This review of marine lipidology deals with recent advances in the field of fatty acids since the end of the 1990s. Different approaches will be followed, mainly developing biomarkers of trophic chains in marine ecosystems and of chemotaxonomic interest, reporting new structures, especially those with biological activities or biosynthetic interest. An important part of this review will be devoted to the major PUFA, their relevance to health and nutrition, their biosynthesis, their sources (usual and promising) and market.

Fatty acid profiles of Mytilus galloprovincialis (Lmk) mussel of subtidal and rocky shore origin

Fatty acid profiles of seeds of the mussel Mytilus galloprovincialis originating from two habitats (rocky shore and subtidal) were compared after transfer to the same habitat (subtidal). The objective was to study the initial levels of different fatty acids of metabolic importance and, furthermore, the variability of these fatty acids over the experimental period. The results show that of all fatty acids identified in both seed groups, the polyunsaturated fatty acids (PUFA) is the group with highest percentage. Within this group, the C20:5n-3 and C22:6n-3 fatty acids show the highest levels. Additionally, the mussels of subtidal origin presented higher initial levels than the rocky shore mussels with regard to fatty acids characterised by energetic-type functions, such as the C14:0, C16:0, and the C20:5n-3 fatty acids, among others. Fatty acids characterised by structural-type functions, e.g. C18:0, C22:6n-3 and non-methylene interrupted dienoic (NMID) with 20 and 22 carbons in rocky shore mussels presented higher levels than those of the subtidal mussels. However, it has not been ruled out that aside from influences relating to the functional aspects of the different fatty acids, the initial differences were also associated with the quantitative and qualitative differences of the available food in both habitats. Nevertheless, 22 days into the experiment (in the majority of cases) the initial differences disappear in the different fatty acids with metabolic importance. On the basis of these results, the influence that mussel origin could exercise on the variability of the fatty acid profiles of recognised metabolic importance is discussed.

Interactive effects of diet and temperature on the scope for growth of the scallop Argopecten purpuratus during reproductive conditioning

Mature individuals of Argopecten purpuratus from suspended culture in Tongoy Bay, northern Chile were conditioned at two temperatures (16 and 20 degrees C) and three different diets (mixture of pure microalgae, microalgae supplemented with lipids and microalgae supplemented with carbohydrates). The food, equivalent to 3% daily of the animal dry weight was supplied continuously by a peristaltic pump. The rates of different physiological processes were measured on 18 scallops (three replicates per temperature/diet combination) during the third week of conditioning. Nine scallops came from the group conditioned at 16 degrees C and other nine from the group conditioned at 20 degrees C (each scallop from a different tank). As in the conditioning experiment, physiological measurements were made in controlled temperature rooms using the same experimental diets. Argopecten purpuratus did not show significant differences in clearance rate between 16 and 20 degrees C when fed with pure microalgae and microalgae+lipids, showing a well known capability of bivalves to acclimate their physiological rates within a certain range of temperature. On the other hand a clear effect of the composition of the diet on the clearance rate was observed. When microalgae were supplemented with a lipid emulsion, clearance rate was highly stimulated, showing values significantly higher in comparison with either pure microalgae, or a mixed diet of microalgae+carbohydrate. These highest feeding rates can be related with the presence of essential fatty acids in the diet, which are considered as very important compounds during the gametogenesis of invertebrates as well as during the development of ova into normal larvae. Thus A. purpuratus can actively regulate clearance rate and does not simply switch between feeding and non-feeding states. The data also suggest the presence of chemical receptors at the level of the gills and/or labial palps, which seem able to detect specific nutritive compounds present in the diet. Absorption efficiency was independent of temperature and was higher with pure microalgae and with microalgae+lipids. The lowest efficiencies were recorded with the diet supplemented with carbohydrates. The energy expended in oxygen uptake and ammonia excretion was very similar in the different experimental diets and temperatures. Scope for growth in A. purpuratus appears mainly affected by the diet and not by temperature. While the lower SFG seems to be associated with diets composed of pure microalgae and microalgae+carbohydrates, the highest values being found for a diet rich in lipids. The data were in agreement with the reproductive conditioning of A. purpuratus, where the highest percentage of ripe scallops occurred in individuals fed with a diet of microalgae supplemented with lipids at both temperatures. Similarly the highest larval survival rate was obtained from gametes released by scallops conditioned with the diet containing lipids.

Effect of diet and temperature upon muscle metabolic capacities and biochemical composition of gonad and muscle in Argopecten purpuratus Lamarck 1819

Recently spawned Argopecten purpuratus broodstock were conditioned at two temperatures and fed three different diets (microalgae, microalgae mixed with lipids and microalgae mixed with carbohydrates) to examine changes in the biochemical composition of gonad and muscle as well as muscle metabolic capacities. During one experiment, scallops were fed at 3% of their dry mass per day whereas during a second experiment, they were fed at 6% of their dry mass per day. During both experiments, total gonadal levels of lipids and protein increased markedly during conditioning with the two mixed diets at 16 degrees C. These increases were less pronounced at 20 degrees C. Carbohydrate gonadal levels only increased during the second experiment at both temperatures and with the three diets. Of the major biochemical components of the adductor muscle, carbohydrate levels changed most during conditioning. Whereas muscle protein levels increased slightly with gonadal maturation, carbohydrate levels dropped considerably. Despite the marked drop in the levels of glycolytic substrates, only the activities of octopine dehydrogenase in the adductor muscle of the scallops conditioned at 16 degrees C consistently decreased. Muscle levels of glycogen phosphorylase were higher in mature than in recently spawned (control) scallops, suggesting a role in the transfer of glucose equivalents from the adductor muscle to other tissues.