Changes in proximate composition,lipid class and fatty acid profile in Greenshell™ mussels (Perna canaliculus) over an annual cycle

Greenshell? mussel (GSM, Perna canaliculus) is New Zealand's most important aquaculture species. This study looked at changes in the proximate composition, lipid class and fatty acid profile of male and female market ready mussels over a year from April 2016 through to March 2017. There were differences over the season as well as differences between male and female mussels. Winter GSM had lower lipid, carbohydrate and protein concentrations than other seasons. Female mussels had a higher lipid (on average 1.8 ± 0.5 g/100 g ww) and carbohydrate (on average 5.0 ± 1.1 g/100 g ww) compared with the males (lipid, 1.5 ± 0.4 g/100 g ww and carbohydrate 4.5 ± 1.2 g/100 g ww). The major differences observed between seasons in the omega 3 and fatty acids content of the GSM were driven by the fat content, with the highest fat content found in female mussels in the spring prior to spawning. The majority of lipids found in mussels are polar lipids. Overall, this study provides the most comprehensive data on the composition and the lipid content of GSM to date and provides solid base‐line data as the New Zealand GSM industry continues to improve their production procedures. The enhanced nutritional payload of mussels harvested outside of winter (particularly female mussels in spring) could drive a differentiated higher value mussel product.     

Importance of the relative levels of dietary arachidonic acid and eicosapentaenoic acid for culture performance of gilthead seabream (Sparus aurata) larvae

The effect of different arachidonic acid (ARA) dietary contents at several dietary eicosapentaenoic acid (EPA) levels on the growth, survival and biochemical composition of gilthead seabream larvae was studied to better define the importance of this fatty acid as a function of EPA. Larvae of 18 days were fed one of the five isonitrogenous and isolipidic microdiets with three different EPA (0.3%, 2% and 4%) and ARA amounts (0.1%, 0.6% and 1.2%). Although a dietary increase in either ARA or EPA alone did not improve survival significantly, the increase in both fatty acids significantly enhanced growth and survival, suggesting an optimum dietary value of EPA:ARA close to 4:1.2. Dietary ARA was more efficiently incorporated into larval tissues than EPA. Increased dietary EPA or ARA contents reduced the incorporation of ARA or EPA into larval lipids, indicating their competition as substrates for different enzymes. The possible negative effect of further elevation of dietary ARA and its competition with EPA for phospholipids synthesis deserves further studies in marine fish larvae.     

Evaluation of macroalgal detritus as food source for juvenile Manila clam,Ruditapes philippinarum: Effects on growth,amino acid content and fatty acid composition

Sufficient high‐quality microalgae are required for indoor nursery of juvenile Ruditapes philippinarum. However, culturing numerous microalgae to support clam feeding is a heavy burden on many hatcheries. The effects of detritus from the macroalgae Ulva pertusa, Chondrus ocellatus and Undaria pinnatifida on the growth, amino acid content and fatty acid profile of R. philippinarum were assessed as potential substitute diets. The green microalga Tetraselmis cordiformis served as comparative diet. Results revealed that the clams ingesting distinct diets presented no significant differences in growth of soft tissues, but the nutritional component of these clams differed dramatically. The clams fed with Undaria + Tetraselmis had the highest content of essential amino acids and proteins. In addition, the clams fed with single macroalgal diets and mixed macroalgal detritus and Tetraselmis showed significantly higher or statistically equal levels in n‐3/n‐6 ratio and docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio with respect to Tetraselmis diets. The relative percentages of EPA and DHA in clams fed with Undaria were 28% and 63% higher than those fed with Tetraselmis, and the arachidonic acid abundances in clams ingesting Undaria + Tetraselmis and Tetraselmis were significantly higher than those in clams ingesting other diets. Together, the diets containing single Undaria or mixed Undaria + Tetraselmis produced Manila clams with nutritional advantages in terms of essential amino acids and polyunsaturated fatty acids. Thus, the detritus of macroalgae, especially Undaria, is an appropriate substitute diet, at least partially, for culture of nutrition‐improved R. philippinarum.     

半滑舌鳎不同家系肌肉中脂肪酸含量的分析

为了研究半滑舌鳎(Cynoglossus semilaevis)不同家系肌肉中脂肪酸的组成与含量,并选育出高营养品系的半滑舌鳎家系,用气相色谱法对同一养殖环境中的半滑舌鳎15个不同家系(164个样本)肌肉中的脂肪酸的组成和含量进行了检测和比较分析,同时对高EPA、DHA、EPA+DHA含量的家系进行筛选,并研究了半滑舌鳎性别与EPA、DHA含量的关系。结果表明:(1)15个家系肌肉中脂肪酸种类没有区别,但脂肪酸的组成和含量存在若干差异。其特征均为多不饱和脂肪酸(PUFA)饱和脂肪酸(SFA)单不饱和脂肪酸(MUFA)。PUFA以ω-3系脂肪酸为主,且ω-3系脂肪酸与ω-6系脂肪酸比值达到4.16~5.03,其中的2种重要ω-3系脂肪酸EPA和DHA在15个家系中均具有显著性差异,且DHA含量远大于EPA含量;筛选出了3个高EPA、DHA、EPA+DHA含量家系,分别为F13012、F13023及F13031。(2)EPA的含量与半滑舌鳎性别不具有显著性相关关系。本研究对于选育半滑舌鳎优良品种家系具有重要意义。     

Effects of Artemia enriched with eicosapentaenoic and docosahexaenoic acid on survival and occurrence of molting failure in megalop larvae of the mud crab Scylla serrata

ABSTRACT:   The present study was conducted to investigate the effect of eicosapentaenoic acid (20:5n-3, EPA) and docosahexaenoic acid (22:6n-3, DHA) on the survival and the occurrence of molting failure to megalops of mud crab Scylla serrata larvae fed enriched Artemia . Survival rate, intermolt period, carapace width at the first crab stage, ratio of chela to carapace length at the fifth zoeal stage and the occurrence of molting failure to megalops were observed. Mud crab larvae were reared in 1-L plastic beakers and fed with Artemia enriched at five different levels of EPA (0.31% to 1.36% EPA; referred to as E25, E50, E75 and E100) or four different levels of DHA (0.75–0.95% EPA and 0.49–1.38% DHA; referred to as D25, D50, D75 and D100). As a negative control, larvae were fed Artemia enriched with oleic acid (OA). Mud crab larvae fed Artemia containing low (0.41–0.45% EPA and trace DHA) or high (1.36% and 0.95% EPA and 0.16% and 1.38% DHA) amounts of EPA and DHA showed a significantly lower survival rate and prolonged intermolt period ( P  < 0.05). Moreover, a high frequency of molting failure to the megalops stage (34 and 33%) occurs coincident with a high chela to carapace length ratio (43 and 44%) in mud crab larvae fed high amounts of EPA and DHA (E100 and D100), suggesting that both of these treatments contain EPA and DHA in excess. These results indicate that during Artemia feeding, EPA and DHA content should be adjusted to 0.71–0.87% and 0.49–0.72% for maintaining a high survival, accelerating the intermolt period, and producing larger carapace width in the first crab stage.     

Changes in lipid content, fatty acid composition and lipid class composition of eggs and developing larvae (0–40 days old) of cultured common dentex (Dentex dentex Linnaeus 1758)

Total lipid content, fatty acid (FA) composition and lipid class composition of common dentex eggs spawned at different times and larvae reared under different culture conditions until 40 days posthatch (dph) were analysed to get a general pattern of lipid composition during larval development. Two groups of larvae were kept under starvation to compare their FA composition with that obtained from normally fed larvae. To compare FA use or accumulation during larval development, results were grouped according to the developmental stage of the larvae instead of age in days posthatch. Saturated and monounsaturated FAs decreased along larval development, while polyunsaturated fatty acid (PUFA) content increased. The ratio of docosahexaenoic acid (DHA)/eicosapentaenoic acid shifted from 4 to 5 in early developmental stages to lower than 1 after metamorphosis. Arachidonic acid levels remained constant along larval development. Larvae kept 6 days under starvation consumed most of their n-3 PUFA while conserving the DHA to values at day 0. The results presented here are useful for the design of nutritional experiments, because there were differences detected in terms of lipid and FA composition between developmental stages with higher differences mainly found in first-feeding larvae and early developmental stages.     

早熟期间中华绒螯蟹肝胰腺指数、肝脂含量及脂肪酸组成的变化

实验采用称量法和气相色谱法分别测定了性早熟前后中华绒螯蟹的肝胰腺指数(HI)、肝脂含量(LC)和肝胰腺脂肪酸组成。雌雄蟹的HI和LC在早熟前后的变化趋势一致,都是早熟个体低于未成熟个体。在性早熟前,雌雄蟹的肝胰腺脂肪酸组成基本一致,只是雌蟹中C20∶5n-3较高(P<0.05)。然而,对早熟前后的个体作比较时,发现雌雄蟹变化情况有很大差异:(1)早熟雌蟹中C16∶1n-7、C16∶0和C18∶0高于未成熟雌蟹(P<0.01),而C20∶5n-3、C20∶4n-6和C22∶6n-3则低于后者(P<0.01);(2)早熟雄蟹中C18∶1高于未成熟雄蟹(P<0.05),而C14∶0(P<0.05)、C16∶1n-7(P<0.05)和C20∶5n-3(P<0.01)皆低于后者。以上结果表明:雌雄蟹在性早熟前后存在肝胰腺脂肪酸组成变化的差异,且C20∶5n-3可能主要参与成熟蜕壳和膜的构建,而C22∶6n-3可能主要参与卵巢发育和卵黄的发生。     

Fatty acid composition,osmolality, Na+, K+‐ATPase activity,cortisol content and antioxidant status of rainbow trout (Oncorhynchus mykiss) in response to various dietary levels of eicosapentaenoic acid and docosahexaenoic acid

This study was conducted to evaluate the effect of dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) levels on the fatty acid composition, salinity tolerance and antioxidant status of rainbow trout (Oncorhynchus mykiss). Four diets were formulated with total EPA and DHA contents of 5.41, 9.55, 13.97 and 17.88 g/kg (abbreviated as ED‐5.41, ED‐9.55, ED‐13.97 and ED‐17.88 respectively). Rainbow trout (initial weight of 90.61 ± 9.25 g) were fed the experimental diets for 8 weeks to accumulate significant differences in fatty acid composition and subsequently underwent salinity acclimation. Our results indicated that high dietary EPA and DHA significantly improved the EPA and DHA content in fish tissues. The serum osmolality of fish returned to their freshwater values in the ED‐9.55, ED‐13.97 and ED‐17.88 groups. The Na⁺, K⁺‐ATPase (NKA) activity of fish in the ED‐13.97 group changed dramatically to adapt the fish to the hypertonic environment. Moreover, there was no significant difference in the serum cortisol concentration and liver catalase (CAT) activity of fish in the ED‐13.97 group during salinity acclimation. The liver superoxide dismutase (SOD) activity in the ED‐13.97 group was significantly higher than that in ED‐5.41 and ED‐9.55 groups at the end of salinity acclimation. The muscle malondialdehyde (MDA) content in the ED‐13.97 group was significantly lower than that in the ED‐17.88 group before salinity acclimation and significantly lower than the ED‐5.41 and ED‐17.88 groups on day 7 of acclimation. The results of this study indicate that the rainbow trout in the ED‐13.97 group exhibited optimal salinity acclimation performance.     

Effect of light,temperature and diet on the fatty acid profile of the tropical sea anemone Aiptasia pallida

Sea anemones of the genus Aiptasia are used as biological models for research and as a prey for the culture of the highly priced ornamental nudibranch Aeolidiella stephanieae. Symbiotic Aiptasia display a remarkable trophic plasticity, being able to fulfil their energetic demands heterotrophically and autotrophically. Consequently, they display a highly variable fatty acid (FA) profile. The objective of the present study was to analyse how light regime (12 h light : 12 h dark versus 24 h darkness), water temperature (22 versus 26 °C) and diet (Artemia nauplii versus enriched Artemia metanauplii) affect the FA composition of A. pallida. The FA profile of wild specimens was also analysed. The dominant FAs of cultured A. pallida were 16:0, 18:1n‐9 and 22:6n‐3. Higher FA levels were recorded when anemones were exposed to light, with this factor explaining the largest amount of variation in the composition of FA profiles. Cultured A. pallida that best mimicked wild anemones were obtained when using a regular light regime, Artemia metanauplii and 22 °C water temperature. Higher FA levels were obtained at a higher temperature and by providing nauplii to cultured anemones. The present study also indicated that A. pallida has the potential to recycle nutrients in marine aquacultures.     

Dummy regression analysis for modelling the nutritionally tailored fillet fatty acid composition of turbot and sole using gilthead sea bream as a reference subgroup category

Farmed turbot and sole were sampled at different stages of the production cycle for analysis of fillet lipid content and fatty acid (FA) composition. The entire data set along with our own published data on gilthead sea bream were fitted to dummy regression equations with turbot and sole as dummy variables, gilthead sea bream as a reference subgroup category, and diet FA composition and fillet lipid content as independent variables. The relative contribution of each independent variable to the total variance was found to vary within and among FAs and fish species, but strong correlation coefficients (0.76 <  r² > 0.99) were found for almost all of the FA equations, including saturated FAs, monoenes and long‐chain polyunsaturated fatty acids (PUFA) of n‐3 and n‐6 series. Given the differences in lipogenic activities of the fish species, major interaction effects between fillet lipid content and dummy variables were found for monoenes and saturated FAs. The proposed equations (hosted at www.nutrigroup-iats.org/aquafat ) were able to fit different proportions of EPA, DPA and DHA underlying the fish species differences in FA desaturation/elongation pathways. The robustness of the model was proven with extra data from the three fish species, allowing a close linear association near to equality for the scatter plot of observed and predicted values.     

Fillet Yield,Biochemical Composition,and Consumer Acceptance of Farmed and Wild Mulloway

The New South Wales prawn aquaculture industry is considering alternative species, such as mulloway (Argyrosomus japonicus), to diversify their production base, but little exists on their market potential. Farmed mulloway had higher levels of fat, energy, and cholesterol than wild mulloway and were an excellent source of long-chain omega-3s with good fillet yields: 46.3% (skin-on) and 38.8% (skin-off). Wild mulloway had higher sodium and moisture content but were a poor source of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). For consumer acceptance, there was a preference for the flavor of wild to farmed mulloway. The high cost of production remains a major constraint to industry growth.     

Importance of dietary arachidonic acid for the growth,survival and stress resistance of larval European sea bass (Dicentrarchus labrax) fed high dietary docosahexaenoic and eicosapentaenoic acids

Together with docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), arachidonic acid (ARA) is being considered to be an essential fatty acid in marine fish larval diets. The objective of the present study was to determine the importance of dietary ARA levels for larval European sea bass performance, when EPA and DHA are also present in the diet. Eighteen‐day‐old larvae were fed, for 14 days, gelatine‐based microdiets containing the following ARA levels: 0.3%, 0.6% or 1.2%. Elevation of dietary ARA up to 1.2% showed a positive correlation with larval survival and a significant improvement in the specific growth rates, body weight and total length. Arachidonic acid was efficiently incorporated into larval lipids, even at a higher proportion than that in the diets. Increased accumulation of ARA did not affect the incorporation of DHA or EPA from the diet into larval total lipids. A significant positive correlation was found between dietary ARA levels and survival after handling stress, indicating the importance of this fatty acid in sea bass larvae response to acute stressors. The results show the importance of ARA for sea bass larvae, but higher dietary levels should be tested to determine whether there is a negative effect of ARA in sea bass as reported for other species.     

Effects of dietary docosahexaenoic acid sources,microalgae meal and oil,on growth,fatty acid composition and docosahexaenoic acid retention of orange‐spotted grouper,Epinephelus coioides

This study evaluated the effects of Aurantiochytrium spp. microalgae meal and oil as dietary docosahexaenoic acid (DHA) sources on the growth, fatty acid composition and DHA retention of orange‐spotted grouper, Epinephelus coioides. Dietary fish oil was replaced with microalgae meal or oil to provide an equal amount of DHA as a fish oil‐containing basal diet. In total, three experimental diets were fed to triplicate groups of fish (initial wt: 8.48 ± 0.06 g) in a recirculating system for 8 weeks. The weight gain and feed efficiency of the fish did not differ significantly among the experimental diets. The fatty acid composition of the whole body of the fish generally reflected the composition of their diet. The concentration of eicosapentaenoic acid in the whole body was higher in the fish fed the fish meal control diet than in those fed the two experimental diets The fish fed the control diet and those fed the diet containing microalgae oil exhibited higher DHA concentrations than did the fish fed the diet containing microalgae meal. The whole‐body DHA retention was the highest in the fish fed the diet with microalgae oil, followed by the fish fed the control diet. The lowest whole‐body DHA retention was observed in the fish fed the diet containing microalgae meal. The results suggested that the oil from Aurantiochytrium spp. microalgae can be used as DHA source for the grouper. DHA utilization by the fish was higher when the diet was supplemented with microalgae oil than with dry microalgae meal.     

Organ and phospholipid class fatty acid specificity in response to dietary depletion of essential n‐3 fatty acids in Atlantic salmon (Salmo salar L.)

The cell membrane phospholipid composition is of major importance for normal cell functions. However, it is not known how complete depletion of both shorter and longer chain omega‐3 fatty acids in salmon diets influences fatty acid composition of phospholipid subclasses in different organs of Atlantic salmon. We describe here the fatty acid composition in phospholipid subclasses of liver, muscle, heart and intestine in Atlantic salmon after 18 months of dietary n‐3 essential fatty acids deprivation. The percentage of 22:6n‐3 was markedly reduced in almost all phospholipid subclasses, and except for muscle phosphatidylcholine, phosphatidylethanolamine (PE) and phosphatidylinositol (PI), phospholipids in deficient fish were totally devoid of 20:5n‐3. As compensation, we observed significant increases in 20:4n‐6, and especially in 20:3n‐9 (Mead acid) and 22:5n‐6, varying among phospholipids and organs. High amounts of 20:3n‐9 were found in liver and intestinal PE, little in PE from heart and muscle. For 22:5n‐6, we saw a small incorporation in PI in liver and intestine compared to heart and muscle. Generally in PI, the preference for 20:4n‐6 to 20:5n‐3 differed significantly between organs. Overall, changes upon n‐3 deprivation seemed to be strongest in liver and intestine, the lipid‐secreting organs, and less in muscle and heart.     

Changes in lipid class and fatty acid composition of adult male Litopenaeus vannamei (Boone) in response to culture temperature and food deprivation

The effects of culture temperature and food deprivation on lipid class and fatty acid composition of adult male Litopenaeus vannamei (Boone) were investigated. Shrimp were maintained in recirculating seawater systems at temperatures of 26 and 32°C and fed 75% dry commercial feed and 25% fresh‐frozen squid for 42 days. Additionally, groups of fed and non‐fed shrimp were maintained at 26°C for 17 days. In shrimp fed at either 26 or 32°C, polar lipids were the main constituents of total identified lipid classes in muscle tissue (66–71%), while neutral lipids were more abundant in hepatopancreas (82–88%). Higher levels of triglycerides were observed in lipids of shrimp hepatopancreas kept at 32°C, but no other lipid class was affected by temperature. A significantly higher proportion of 22:6n‐3 was consistent in muscle and hepatopancreas polar and neutral lipids of shrimp maintained at 26°C. In response to food deprivation, the amount of polar lipids, but not neutral lipids, was reduced by approximately 28% in muscle tissue, whereas all lipid reserves were almost depleted in the hepatopancreas. The variable consumption of some individual fatty acids was observed in polar and neutral lipids of both tissues.     

Effects of dietary DHA/EPA ratios on growth performance,survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus)

This study was conducted to investigate the effects of dietary docosahexaenoic to eicosapentaenoic acid (DHA/EPA) ratios on growth performance, survival and fatty acid composition of juvenile swimming crab (Portunus trituberculatus). Four isonitrogenous and isoenergetic experimental diets were formulated to contain different DHA/EPA ratios (0.70, 0.84, 1.06 and 1.25). There were three replicates (15 crabs per replicate) for each diet treatment. The crabs were fed (about 6–8% body weight) twice daily for 8 weeks. A good growth performance and feed utilization were observed in swimming crabs fed the diets with DHA/EPA ratios of 0.70 and 0.84. Crabs fed diet with 0.70 DHA/EPA ratio showed a significantly higher weight gain (WG) compared with the crabs fed the diet with DHA/EPA ratio of 1.25 (P < 0.05). The result of this study showed that the survival increased with decreasing the ratio of DHA/EPA. The DHA/EPA ratios in polar lipid from tissues were influenced by the dietary DHA/EPA ratios. Results of this study indicated that the growth performance and survival of juvenile swimming crab are correlated to the DHA/EPA ratio in the diets, and the best growth performance and survival were achieved with the ratios of 0.70–0.84.