Marrit Caers

The effect of lipid supplementation on growth and fatty acid composition of Tapes philippinarum spat

The present study investigated the possible use of emulsions as an artificial lipid supplement to live algae for seed of the Manila clam Tapes philippinarum. The uptake and assimilation of an emulsion, rich in docosahexaenoic acid (DHA, 22:6n−3) and eicosapentaenoic acid (EPA, 20:5n−3) and fed at concentrations of 20 and 40% of the algal dry weight, were verified analytically by fatty acid analysis of the animals and their diets. Dietary requirements for n−3 highly unsaturated fatty acids (HUFA) were examined by supplementing Dunaliella tertiolecta, which contains no polyunsaturated fatty acids longer than 18:3n−3 and Tetraselmis suecica, which contains EPA but only trace amounts of DHA. An algal mixture of Isochrysis galbana (clone T-Iso) and Chaetoceros neogracile (1:1, on dry weight basis) was used as the control diet. After 4 weeks, the lipid supplementation resulted in a significant increase of the DHA level in the seed compared to the animals fed non-supplemented Dunaliella (from 9.5 to 19.8 and 22.0% at a supplementation of 20 and 40%, respectively) or Tetraselmis (from 3.4 to 24.8 and 26.9%, at a supplementation of 20 and 40%, respectively) diet. Feeding solely D. tertiolecta resulted in a significantly lower daily growth rate (DGR) compared to animals fed T. suecica or the mixed algal diet. Lipid supplementation improved the DGR of the clams fed D. tertiolecta while hardly any effect could be detected in those fed T. suecica. The poor nutritional value of D. tertiolecta was indicated by the continuous decrease of the DGR and resulted in a DGR that was no longer significantly different from the starved ones at the end of the experiment.

Dietary impact of algal and artificial diets, fed at different feeding rations, on the growth and fatty acid composition of Tapes philippinarum (L.) spat

Abstract The effect of lipid supplementation and algal ration on growth and fatty acid composition of juvenile clams, Tapes philippinarum was investigated. A diet of Tetraselmis suecica was supplemented with a lipid emulsion and fed at a daily ration of 0.5, 1.0 and 1.5% WW DW−1 day−1. A mixed algal diet of Isochrysis galbana (clone T-Iso) and T. suecica (1:1 on DW basis) and starvation functioned as positive and negative control treatments, respectively. T. suecica, which contains eicosapentaenoic acid (20:5n−3) but no docosahexaenoic acid (22:6n−3), was supplemented with 50% (% of algal dry weight) of a 22:6n−3-rich emulsion. Higher growth rates of T. philippinarum were associated with higher T. suecica feeding rations. Lipid supplementation resulted in significantly better growth rates of T. philippinarum at a T. suecica ration of 0.5, 1.0 and 1.5% WW DW−1 day−1. The growth promoting effect of lipid supplementation was significantly reduced during 4 consecutive weeks or by increasing the algal feeding ration. Increasing T. suecica rations were associated with a decrease in the % composition of 22:6n−3 while the 20:5n−3% composition was hardly affected in the total lipids of T. philippinarum. On the contrary, the absolute concentration of 22:6n−3 (μg per gram dry weight, μg g DW−1) in the total lipids of T. philippinarum was similar at all T. suecica rations while the 20:5n−3 concentration significantly increased. The major effect of lipid supplementation on the fatty acid composition of the clams, was a significant increase of the 22:6n−3% composition in the total lipids, polar lipids and triglycerides. In contrast with 20:5n−3, the effect of lipid supplementation on the absolute 22:6n−3 content (μg g DW−1) was more pronounced at a higher T. suecica ration. After a starvation period of 4 weeks, the concentration (μg g DW−1) of all fatty acids was significantly reduced, except the n−7 monoenoic fatty acids (MUFA) and the non-methylene interrupted dienoic fatty acids (NMID). The concentration (μg g DW−1) of the NMID in starved clams and clams fed different diets was similar to the concentration in the initial sample. This indicated that growing spat was actively synthesising NMID and they were selectively retained in unfed animals. The results indicated that either dietary lipid or 22:6n−3 was a growth-limiting factor when T. suecica was fed at a ration of 0.5, 1 and 1.5% WW DW−1 day−1. A selective retention in starved clams and a preferential accumulation in fed clams was observed for 22:6n−3 but not for 20:5n−3 which indicated a greater importance of 22:6n−3 compared to 20:5n−3.

Impact of algal diets and emulsions on the fatty acid composition and content of selected tissues of adult broodstock of the Chilean scallop Argopecten pupuratus (Lamarck, 1819)

Abstract The impact of dietary fatty acids on the fatty acid composition and content in different organs (digestive gland, adductor muscle and male and female gonad) of Argopecten purpuratus was evaluated during the process of gonad maturation under controlled laboratory conditions. A mixed algal diet of Isochrysis galbana (clone T-Iso), Pavlova lutheri , Chaetoceros gracilis and Tetraselmis suecica was either fed alone (Al) or supplemented with 50% lipids (expressed as % of the algal dry weight (DW)) using an emulsion rich in 22:6 n −3 (Al+EmDHA) or an emulsion rich in 20:5 n −3 (Al+EmEPA). Results showed the algal diet having the greatest impact on the fatty acid composition (mainly an increase of 18:1 n −9, 18:2 n −6; 18:3 n −3 and a decrease of 20:5 n −3) of the digestive gland and female gonad, moderate in the male gonad while the fatty acid composition of the adductor muscle was hardly affected. Our data indicated that 16:1 n −7 and 18:1 n −9 were partially elongated to 18:1 n −7 and 20:1 n −9, respectively. The supplementation of the algal diet with EmDHA or EmEPA (which contained 45% and 19% 22:6 n −3, respectively) increased significantly the concentration of 22:6 n −3 (mg g −1 DW) in the digestive gland, female gonad and male gonad with 78%, 57% and 51%, respectively, for (Al+EmDHA)-fed scallops and 18%, 33% and 19%, respectively, for (Al+EmEPA)-fed scallops, while the 22:6 n −3 concentration in the adductor muscle was not affected. Broodstock conditioning was associated with a significant increase of the lipid content in the female and to a lesser extent in the male gonad. The significant increase (as compared to the initial sample) of the 22:6 n −3 concentration in the digestive gland, female gonad and eggs of A. purpuratus fed 22:6 n −3-rich lipid illustrated that recently ingested fatty acids did significantly contribute to the lipid accumulation process in the maturing female gonad. The similarities between the fatty acid composition of the female gonad and digestive gland suggest that lipids were transferred from the lipid-rich digestive gland to the female gonad.

The Chilean scallop Argopecten purpuratus (Lamarck, 1819): I. fatty acid composition and lipid content of six organs

This paper describes the distribution of lipids and fatty acids in different organs of Argopecten purpuratus broodstock. The female gonad and the digestive gland showed the highest lipid content, moderate lipid levels were present in the gills and male gonad while the mantle and especially the adductor muscle exhibited the lowest lipid content. A principal component analysis of the fatty acids of the total lipids separated the organs in four major groups: gills and mantle (I), adductor and male gonad (II), female gonad (III) and digestive gland (IV). A special feature of the gills and mantle was the presence of high levels of plasmalogens recognized by the peaks for vinyl methyl ethers from dimethylacetal degradation accompanying peaks for methyl esters of fatty acids in the GC profiles, and an unidentified fatty acid (22?). The highest level of n-3 polyunsaturated fatty acids (mainly EPA and DHA) was found in the adductor. Similarities between the fatty acid composition of the triglyceride fraction of the female gonad and the digestive gland (e.g. the high level of 14:0 and 18:4n-3) indicated the transfer of lipids from the lipid-rich digestive gland to the female gonad. Trimethyltridecanoic acid (TMTD) was found nearly exclusively in the polar lipid fraction of the digestive gland.

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

Dietary supplementation with lipid emulsions during broodstock conditioning of Argopecten purpuratus was used to manipulate the fatty acid composition of the eggs. The scallops were fed a mixed algal diet either alone (Al) or supplemented with an emulsion rich in ethyl esters of docosahexaenoic acid (DHA; Al+EmDHA) or eicosapentaenoic acid (EPA; Al+EmEPA) at a concentration of 50% lipids per algal dry weight (DW). The longer induction period and the lower fecundity in scallops fed solely on algae indicated a higher food value for the lipid-supplemented diet compared to the non-supplemented diet. Lipid supplementation resulted in a significant increase of the total lipid content (mg/g DW) of the eggs. The fatty acid quality of the diet had no significant effect on the fatty acid profile of the polar lipids. However, the supplementation of the DHA-rich emulsion resulted in a significant increase of the DHA level (% of total fatty acids) in the total and neutral lipids of the eggs compared to eggs from scallops fed solely algae. The absolute DHA content (mg/g DW) increased by 47%. The EPA level in the total and neutral lipids of eggs from broodstock supplemented with EmEPA was significantly higher than in eggs from scallops fed Al+EmDHA but no significant differences were detected with eggs from the non-supplemented diet (Al). The absolute EPA concentration in eggs from scallops fed Al+EmEPA was, respectively, 19 and 17% higher than in eggs from broodstock fed, respectively, solely algae (Al) or Al+EmDHA. The results illustrated that fatty acids, supplied as emulsified ethyl esters, could be ingested and assimilated by adult A. purpuratus and were at least partially allocated to the eggs.

Incorporation of different fatty acids, supplied as emulsions or liposomes, in the polar and neutral lipids of Crassostrea gigas spat

Abstract Pacific oysters spat ( Crassostrea gigas ) were fed an algal diet ( Tetraselmis suecica ) whether or not supplemented with emulsions or liposomes rich in 18:1 n −9, 18:2 n −6 and 22:6 n −3. The preferential accumulation and partitioning of the latter fatty acids between the polar and neutral lipids of C. gigas spat were followed. Additionally, the efficiency of emulsions and liposomes as fatty acid carriers for C. gigas spat were compared. The incorporation of dietary fatty acids was found to vary substantially according to the fatty acid carrier (emulsions vs. liposomes), the particular fatty acid (18:1 n −9, 18:2 n −6 or 22:6 n −3), and the lipid fraction (neutral vs. polar lipids). A comparison of the percentage (% of the total fatty acids) and absolute concentration (mg g −1 dry weight) of 18:1 n −9, 18:2 n −6 and 22:6 n −3 in the total lipids of C. gigas fed solely T. suecica or lipid-supplemented diets, suggest the following order of preferential accumulation: 22:6 n −3>18:1 n −9>18:2 n −6. Unlike 22:6 n −3 which was accumulated in both the neutral and polar lipid fraction of C. gigas , 18:2 n −6 and 18:1 n −9 were mainly deposited in the neutral lipids. High dietary supplies of n −6 and/or n −3 PUFA seriously altered the n −3/ n −6 PUFA ratio in the neutral as well as polar lipids of spat. The fatty acid profile of emulsion-fed spat indicated a rather limited ability to elongate 18:2 n −6 to 20:2 n −6 whereas no clear evidence for desaturation to 20:4 n −6 was observed. Irrespective of the diet, nonmethylene-interrupted-dienes and plasmalogens (detected as dimethylacetals) were abundant and located nearly exclusively in the polar lipids. The ash free dry weight (AFDW) of emulsion-fed spat was significantly higher than the AFDW of liposomes-fed spat which was in turn significantly higher than the AFDW of oysters fed solely algae. The growth and fatty acid composition of liposomes-fed oysters illustrated their inferior efficiency as compared with emulsions to supplement algal diets with fatty acids. This could have been related to the small size of the liposomes vs. an emulsion.