Yanic Marty

The effect of monospecific algal diets on growth and fatty acid composition of Pecten maximus (L.) larvae

Abstract Four batches of Pecten maximus (L.) larvae were grown under hatchery conditions and fed the monospecific diets Pavlova lutheri Droop, Isochrysis aff. galbana Green (clone T-iso; termed Tahitian Isochrysis), Chaetoceros calcitrans Takano and Dunaliella tertiolecta Butcher which were selected on their very different polyunsaturated fatty acid (PUFA) profiles. Neutral and polar lipid PUFA compositions of larvae were influenced by diets. The constant level of (n-3) PUFA in neutral lipids of larvae although very different in the diet indicated that neutral lipid composition was partially controlled by the larval metabolism. Similarly, the stability of total saturated, monounsaturated and PUFA levels (25, 15 and 55% of total fatty acids), as well as total (n-3) PUFA level and the preferential incorporation of the 22:6(n-3) in polar lipids clearly indicated a metabolic regulation of the fatty acid composition. The 20:4(n-6) and 22:5(n-6) acids were also preferentially incorporated. The accumulation of 18:3(n-3) or 20:5(n-3) with depletion of 22:6(n-3) in neutral and polar lipids of larvae fed diets with high levels of the first two fatty acids but little or no 22:6(n-3), indicated that elongation-desaturation of dietary fatty acids was too low in P. maximus larvae to maintain high 22:6(n-3) levels in polar lipids. The selective incorporation of dietary long chain PUFA into neutral and polar lipids by acyltransferases may be the main mechanism controlling the fatty acid composition of larvae. These results indicate that P. maximus larvae have essential requirements for long chain (n-3) and (n-6) PUFA, similar to many other marine species.

Changes in the fatty acid composition of Pecten maximus (L.) during larval development

The fatty acid composition of Pecten maximus (L.) larvae grown under hatchery conditions was determined during development from the oocyte stage to the pediveliger stage (Day 23). The levels of total fatty acids in neutral and polar lipids increased 3 days after the first feeding and were ≈10 times higher in pediveligers than in D-larvae (32.46 vs. 3.14 ng·larva−1 and 11.38 vs. 1.23 ng·larva−1 in neutral and polar lipids, respectively). The proportions of total saturated, monounsaturated and polyunsaturated fatty acids in neutral and polar lipids remained stable throughout the development. The fatty acid composition of P. maximus larvae was typical of that described for other marine bivalve larvae since the (n-3) polyunsaturated fatty acids (PUFA) formed 34.4–39.6% of the neutral lipids and 43.0–50.7% of the polar lipids. The major PUFA identified in oocytes and larvae were similar to those supplied by the diet [18:2(n−6), 18:4(n−3), 20:5(n−3) and 22:6(n−3)]. We observed that significant changes of the PUFA composition occurred in neutral and polar lipids during embryogenesis and the subsequent nutritional transition. These changes were expressed by the relative decline of the 20:5(n−3) and 20:4(n−6) percentage levels in both lipid fractions while the 22:6(n−3) increased in neutral lipids and the 22:5(n−6) increased in both neutral and polar lipids. We observed also that polar lipids exhibited a 22:6(n−3) level considerably higher than that of the diet (26.8 vs. 6.8%) and constant throughout development, indicating a preferential incorporation and a major structural role. These results suggest that a metabolic control of the fatty acid composition of neutral lipids and mainly polar lipids takes place in developing larvae. With reference to previous studies on fatty acid metabolism of molluscs, it is probable that this control results from a selective incorporation of dietary fatty acids by acyltransferases rather than a desaturation of dietary precursors. P. maximus larvae seem therefore to have a high nutritional requirement for long chain PUFA and especially the 22:6(n−3).

Effect of food fatty acid and sterol quality on Pecten maximus gonad composition and reproduction process

Abstract Spawning individuals of the scallop Pecten maximus were conditioned on three test diets: Tahiti Isochrysis , a mixture (PTSC) and Chaetoceros calcitrans . The scallops fed T- Isochrysis showed a better hatching rate and lower atresia than those fed the other two diets. Proximate composition of the female gonads was not modified by the differences in the diets. Enrichment of gonads with sterol esters and triglycerides, characteristic of storage of lipids, observed with the broodstock fed the diatoms, did not result in successful gametogenesis and spawning. The monounsaturated fatty acid (MUFA) and polyunsaturated fatty acid (PUFA) composition of neutral and polar lipids of gonads was related to the fatty acid composition of the diet. However, the 20 and 22 carbon PUFA were maintained at levels relatively independent of those of the diet; when these fatty acids were low in the diet, their concentration in the lipids of the gonads decreased but still remained significant. This effect was more pronounced in the polar than the neutral lipids. The preferential incorporation of 22:6 n − 3, 20:4 n − 6 and 20:5 n − 3 in the polar lipids indicates their role in gametogenesis and embryogenesis. The sterol composition of the gonads (free sterols and sterol esters) reflected that of the diet; however, the cholesterol, mainly found in the esterified fraction, was maintained at stable levels independent of dietary supply. Two sterols (22-dehydrocholesterol and 24-methylenecholesterol) that were either absent from, or present only in trace amounts in the diets, were found to occur at constant levels in the female gonads, regardless of the nature of the diet.

Fatty acids and sterols in domestic wastewaters

Raw and treated sewage from physical-chemical and biological wastewater treatment plants were analysed for fatty acids and sterols by HPLC and GC. Raw sewage fatty acid and sterol concentrations varied widely during a diel cycle but their composition remained almost the same. Fatty acids were represented mainly by four components: 16:0, 18:0, 18:1(n-9) and 18:2(n-6). Three 5β-stanols: coprostanol, 24-methylcoprostanol and 24-ethylcoprostanol, accounted for 50–60% of the total sterols, and the coprostanol/cholesterol and the 24-ethylcoprostanol/β-sitosterol ratios were greater than 1. These characteristics were still recognizable in the treated sewage from physical-chemical and biological treatment plants. Removal was more efficient with the biological treatment than with the chemical one, especially for the dissolved compounds. It is estimated that 223 kg of fatty acids and 11 kg of sterols are released daily into the bay of Toulon by the Toulon-Est treatment plant while 74 kg of fatty acids and 5 kg of sterols are discharged into the Morlaix River estuary every day. In general, treated or raw sewages supply 0.1–8 g/day/cap of fatty acids and 0.01–0.6 g/day/cap of sterols to the surrounding environment.

Comparison of the lipid class and fatty acid composition between a reproductive cycle in nature and a standard hatchery conditioning of the Pacific Oyster Crassostrea gigas

Abstract The lipid composition of Crassostrea gigas was analyzed during the reproductive phase in natural as well as under artificial conditions. The lipid content increased and accumulated in the gonads, but to a higher extend in the naturally conditioned animals. The percentage of neutral lipid in total lipid of the gonad plus mantle was stable, high (>70%) and equal under both conditions, underscoring that the lipid reserves were preferentially located in that organ. The composition of the polar lipid classes was stable with little variations. The fatty acid (FA) composition of the neutral lipids in all organs is influenced by diet. However, there is a different response according to organs. A high dietary impact occured in the digestive gland whereas the muscle was less affected. The polyunsaturated fatty acid (PUFA) level of the neutral and polar lipids in the gonads changed little despite the dietary conditions but the respective proportions of (n-3) and (n-6) PUFA differed drastically as a result of diet composition. There was clear evidence in all organs for a specific accumulation of 22:6(n-3) and 20:5(n-3) in the polar lipids under both conditioning diets. The proportions of 22:6(n-3) and 20:5(n-3) from neutral and polar lipids of oysters conditioned artificially were significantly lower than of those that were naturally conditioned.

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∶1n−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∶1n−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∶1n−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.

Changes in mitochondrial oxidative capacities during thermal acclimation of rainbow trout Oncorhynchus mykiss: roles of membrane proteins, phospholipids and their fatty acid compositions

SUMMARY Changes in the properties of mitochondria from oxidative muscle of rainbow trout Oncorhynchus mykiss were examined during warm (5°C to 15°C) acclimation. Trout were studied shortly after the initial thermal change and after 8 weeks acclimation to 15°C. To identify potential mechanisms by which oxidative capacities change, the modifications of phospholipid composition, membrane proteins and functional capacities of red muscle mitochondria were examined. Marked functional changes of isolated muscle mitochondria during warm acclimation of rainbow trout were reflected by a host of modifications in phospholipid composition, but by few shifts in protein components. Shortly after transfer of trout from 5°C to 15°C, the maximal oxidative capacity of mitochondria measured at 15°C increased slightly, but rates at both assay temperatures (5°C and 15°C) decreased markedly after warm acclimation. The increase in capacity in short-term warm exposed trout was most pronounced when rates at 15°C were expressed relative to cytochrome a and c1 levels. Non-phosphorylating (State 4) rates of oxygen uptake increased with short-term warm exposure before returning to initial levels after warm acclimation. Cytochrome c oxidase (CCO) activity in the mitochondrial preparations decreased with warm acclimation. The thermal sensitivity of the ADP affinity was markedly modified during short-term warm exposure, when the ADP/O ratio increased, but warm acclimation returned these values to those observed initially. ADP affinity increased after warm acclimation. Changes in the mitochondrial content of cytochromes and adenine nucleotide translocase (ANT) could not explain these patterns. On the other hand, changes in the proportions of the lipid classes and in the acyl chain composition of certain phospholipid classes mirror the modifications in functional properties. Short-term exposure to 15°C decreased the ratio of diacylphosphatidylethanolamine/diacylphosphatidylcholine (diacylPE/diacylPC), whereas warm acclimation led to restructuring of fatty acids (FA) and to increases of plasmalogen forms of PE and PC. Modification of overall membrane unsaturation did not appear to be the primary aim of restructuring membrane FA during warm acclimation, as total mitochondrial phospholipids and the major phospholipid classes only showed slight shifts of their acyl composition with warm acclimation. On the other hand, natural lysophosphatidylcholine (LysoPC) showed dramatic changes in FA content, as 16:0 and 18:1n-9 doubled whereas 22:6n-3 decreased from around 50% to 32% in warm acclimated trout. Similarly, in cardiolipin (CL), the levels of 16:0 and 18:1n-7 halved while 18:2n-6 increased to over 20% of the FA with warm acclimation. Given the central role of CL in modulating the activity of CCO, F0F1-ATPase and ANT, these changes suggest that specific compositional changes in CL are important modulators of mitochondrial capacities. The many structural changes in membrane lipids contrast with the limited modifications of the membrane protein components examined and support the concept of lipid structure modulating mitochondrial capacities.

Growth and lipid class composition of Pecten maximus (L.) larvae grown under hatchery conditions

Abstract Five independent batches of Pecten maximus (L.) larvae, reared under the same standard hatchery conditions, showed different growth rates, ranging from 1.9 to 6.6 μm·day −1 . A standard lipid profile was defined based on the fast-developing larvae and variations to this standard were seen when abnormal growth performances occurred. The lipid class composition was determined during the development of D-larvae to Day 23 using chromarods and flame ionization detection. Phospholipids and triglycerides were the main lipid classes in P. maximus larvae as reported for other cultured bivalve larvae (accounting for 50 and 37% of total lipids, respectively). Sterols and free fatty acids formed 10 and 3% of the total lipids, respectively. These relative proportions of lipid classes were constant during development of fast developing larvae. The triglyceride:organic matter ratio (TG:OM) stabilized after an initial decline during 3 days after the first feeding and the increase of triglycerides after this time indicated that the catabolism of endogenous triglycerides was rapidly offset by the food intake during the nutritional transition. The comparison of this lipid class pattern with those from larvae which exhibited a lower growth rate revealed that: (i) no stability of the lipid class composition was apparent throughout development; (ii) the triglyceride:total lipid (TG:TL) ratio in D-larvae was not related to the subsequent growth; (iii) a low TG:OM ration in D-larvae was related to poor growth while higher levels did not correspond necessarily to better growth rates; (iv) both the degree and the duration of the TG:OM ration decline for all these batches during the 1st wk can be related to the ability of the larvae to overcome the nutritional transition from trochophore to veliger rapidly and allow for subsequent successful growth. The possible influence of uncontrolled genetic or environmental factors is suggested.

Impact of the quality of dietary fatty acids on metabolism and the composition of polar lipid classes in female gonads of Pecten maximus (L.)

Abstract The impact of dietary deficiency of the essential fatty acids 20:5(n-3), 22:6(n-3) and 20:4(n-6) was studied at the level of different polar lipid classes that constitute the membrane structure of female gonads of Pecten maximus by using three microalgal diets. After 11 weeks of conditioning of the broodstock, the relative percentages of polar lipid classes were very little, or not at all, influenced by the composition of the microalgae. On the other hand, the imprint of dietary fatty acid composition was reflected in the relative composition of fatty acids specific to some classes but not all of them. The dietary fatty acid composition thus clearly influenced that of phosphatidylcholine (PC), the plasmalogens and to a smaller extent the phosphatidylserine (PS) and phosphatidylethanolamine (non plasmalogen PE), but not of phosphatidylinositol (PI) and the glycolipid (GLY). The PI showed a very stable composition and was rich in 20:4(n-6) (>30%) irrespective of the diet. Likewise, the 22:6(n-3) content was consistently higher than 76% in the glycolipid. The maintenance of the specific fatty acid composition of these classes is probably a physiological necessity for gametogenesis and embryogenesis.

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

The major phospholipid classes in the larvae of the scallop Pecten maximus were phosphatidylcholine (PC) and plasmalogens (PLSM) (35.5 and 32.1 mol%, respectively). The minor classes were glycosyldiacylglycerol-like (GLY), phosphatidylinositol (PI), phosphatidylserine (PS) and non-plasmalogen phosphatidylethanolamine (PE) at 6.7, 9.1, 8.5 and 8.1 mol%, respectively. Abundance of phospholipid classes and their content of saturated, monounsaturated and polyunsaturated fatty acids remained relatively conserved during the course of larval development. During larval development there was a decrease in the amount of 20-carbon polyunsaturated fatty acids (PUFA) in the polar lipids, while the amount of 22-carbon PUFA remained constant. These changes, which occurred mainly during the lecithotrophic phase, imparted a specificity in PUFA composition to the different classes of polar lipids. During this phase, 20:5(n 3) replaced 20:4(n 6) in PI but decreased sharply in PLSM and, to a lesser extent, in PC. After the initial phase of composition changes, the fatty acid composition of the polar lipid classes became stable, with specific associations of some of the PUFA with certain polar lipid classes: 22:6(n 3) with GLY, 20:5(n 3) with PE, 20:4(n6) with PI. The 22:6(n3):20:5(n3) ratio in PLSM during exotrophy was always twice as high as in the PC fraction.