Changes in lipid class and fatty acid composition during development in pike (Esox lucius L) eggs and larvae

To establish the changes which occur during embryogenesis and early larval development, eggs, yolk sac larvae and swim-up larvae of pike were examined for lipid class and fatty acid composition. At a water temperature of 15.5°C, the embryonic phase was short (6 days) and characterized by a 41.3% decline in the lipid content of eggs, accompanied by large reductions in the amount of phosphatidylcholine (41.4% decrease), sterol esters and triacylglycerols (respectively a 41.2% decrease and a 58.1% decrease), but not phosphatidylethanolamine which increased markedly (35.6%). By the time of yolk sac absorption (7 to 11 days after fertilization) the larvae remained inactive and a limited utilization of lipids was observed. Yolk sac phosphatidylcholine was selectively incorporated into larval bodies while the levels of other lipid classes remained unchanged in the yolk. When the swim bladder was filled and the swimming stage was reached (11 days to 13 days af), the yolk was completely depleted and yolk phosphatidylcholine together with yolk triacylglycerols were catabolised. Yolk phosphatidylethanolamine and yolk sterol esters were partly incorporated into the body lipids. In the subsequent swim-up larval stage (13 to 15 days af), a steady decrease in lipids was observed (41.6%). Fluctuations in the levels of polyunsaturated fatty acids, monounsaturated fatty acids or saturated fatty acids examined from eggs or larvae were consistent with changes in lipid classes during pike development. During yolk sac absorption, pike incorporated yolk PUFA released on hydrolysis of phosphatidylcholine into the larval body. The results are discussed with reference to water temperature and in relation to the ontogenic and ecological context of pike development. This revised version was published online in July 2006 with corrections to the Cover Date.     

Comparison of the lipid profiles from wild caught eggs and unfed larvae of two scombroid fish: northern bluefin tuna (<Emphasis Type="Italic">Thunnus thynnus</Emphasis> L., 1758) and Atlantic bonito (<Emphasis Type="Italic">Sarda sarda</Emphasis> Bloch, 1793)

Lipids and essential fatty acids are determinants of the reproductive process in marine fish, affecting fecundity, egg quality, hatching performance, pigmentation and larval malformation. We have analyzed and characterized the lipids of eggs and unfed larvae of two wild caught scombroid fish, the Atlantic northern bluefin tuna (Thunnus thynnus) and Atlantic bonito (Sarda sarda). Dry matter and total lipid contents, polar and neutral lipid classes and total lipid fatty acid contents were determined in the eggs of bluefin tuna and eggs and unfed larvae during the development of Atlantic bonito. Bluefin tuna eggs had slightly but significantly more dry mass than bonito eggs but very similar lipid content. However, bluefin tuna eggs presented a higher polar lipid content due to increased proportions of phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI). Bonito eggs and larvae showed increasing dry mass and decreasing lipid content with development. The proportion of polar lipids increased due to increased PE, PS and PI, whereas choline-containing polar lipids (phosphatidylcholine and sphingomyelin) remained relatively constant. Free cholesterol also increased, whereas the levels of other neutral lipids, especially triacylglycerol and steryl ester fractions, decreased, presumably due to utilization for energy to drive development. Bluefin tuna eggs had higher levels of n − 3 and n − 6 highly unsaturated fatty acids due to higher docosahexaenoic and arachidonic acid contents, respectively, than bonito eggs. The results are discussed in relation to the lipid and fatty acid requirements of larval scombroid fish in comparison to those of other larval marine finfish species under culture conditions.     

Lipids in female northern bluefin tuna (Thunnus thynnus thynnus L.) during sexual maturation

Total lipids, lipid classes, fatty acids and vitamin E contents were measured in ovary, liver, dark muscle, white muscle and mesenteric perigonadal fat in four maturational stages of Atlantic female northern buefin tuna (Thunnus thynnus thynnus L.) during migration to Mediterranean spawning grounds through the Strait of Gibraltar. Ovary lipid content increased significantly by 37.6-fold from inmature to spawning stage, accumulating large quantities of steryl/wax esters, whereas the ratio of mesenteric perigonadal fat (primarily triacylglycerols) weight to ovary weight decreased linearly throughout maturation. In contrast, liver, dark red and white muscles lipid content did not show a major depletion during maturation compared to that of perigonadal fat. The fatty acid composition of ovary from bluefin tuna showed that docosahexaenoic acid (DHA; 22:6n-3) was the most abundant fatty acid and DHA: EPA: AA and DHA: EPA ratios were 19.3/4.3/1 and 4.5/1, respectively. Neutral lipids predominated over polar lipids (2-3:1) in ovary and triacylglycerol and steryl/wax ester were major lipid classes. In general, fatty acid composition of most tissues examined were similar to each other but, in contrast, the fatty acid profile of perigonadal fat was rich in monoenes such as 18:1n-9, 20:1n-9 and 22:1n-11, and DHA decreased significantly at spawning stage. The total lipid balance suggested for the disappearance of lipid from perigonadal fat depots and, to a lesser degree, from muscle and liver depots, reflected lipid utilization for gonadal development on the one hand and non-gonadal metabolism in the other. The former included lipid transferred to the gonad and lipid catabolized to provide metabolic energy for the biosynthesis of gonadal constituents and the later was likely to be lipid catabolism to provide energy for swimming during spawning migration. This revised version was published online in August 2006 with corrections to the Cover Date.     

Effects of fish hydrolysate (CPSP®) on growth and digestive gland lipid composition of Octopus vulgaris (Cuvier, 1797) juveniles

Effects of artificial diets were tested on growth and digestive gland (DG) lipid composition of juvenile Octopus vulgaris. For Experiment I, three diets were used: (i) SQUID (Loligo gahi) as a control diet; (ii) Squid paste and fish hydrolysate CPSP^®, agglutinated with gelatine (GEL20); and (iii) Squid paste, fish hydrolysate CPSP^® and gelatine (GEL40). For Experiment II, three diets were used: (i) SQUID, control diet; (ii) Squid paste, CPSP^® and alginate (ALG10); and (iii) Squid paste, CPSP^® and alginate (ALG20). For both experiments, growth rates for octopuses fed control were higher (P < 0.05), while artificial diets were not different (P > 0.05) between them. All diets promoted similar growth, regardless of the different CPSP^® concentrations and binders. Growth rates obtained were among the highest obtained for O. vulgaris with artificial diets until now. The lower growth obtained with the artificial diets was greatly reflected in the DG fatty acid composition. The most important fatty acid groups, such as n‐3 highly unsaturated fatty acids, decreased in the DG of animals fed artificial diets. Lipid content, particularly neutral lipids, was higher in the DG of octopuses fed squid, indicating higher nutritional condition of these animals compared to those fed the artificial diets.     

Lipid distribution in branching coral Montipora digitata

>ABSTRACT: The lipid profile was studied along the branch length, from the top, middle to base portion, of coral Montipora digitata to gain more insight into the physiological significance of lipids in the coral energy budget. The lipids of M. digitata consisted of seven major lipid classes: polar lipid, sterol, free fatty acid, unknown lipids 1 and 2, triacylglycerol (TG), and wax ester. The concentration of storage lipids, TG, and wax ester showed a top–base gradient along the length, whereas the levels of free fatty acid and unknown lipids showed a base–top gradient. The proportions of polar lipid and sterol in the top portion of the branch were slightly higher than those in the base portion. This observation appeared to be compatible with the view that the increased energy expenditure for proliferation enhanced the mobilization of the storage fuel lipids of wax ester and TG rather than the structure lipids of polar lipids and sterols at the top portion of the branch. Compositions of fatty acid also showed a length-wise diversity. The top portion had a lower proportion of palmitic acid (16   :   0) in all lipid classes of fatty acid ester, suggesting that this fatty acid was preferentially mobilized at the top portion, probably for the growth of coral cells.     

Annual cycle of plasma lipids in captive reared striped bass: effects of environmental conditions and reproductive cycle

Protein, lipid and fatty acid concentrations in plasma of eight male and eight female six year old captive striped bass (Morone saxatilis) were monitored monthly over the course of two reproductive cycles as part of an effort to investigate the time course of lipid class mobilization and subsequent deposition in gonads. Total protein levels (44.2 ± 0.67 mg ml^–1, range 20.6–86.4) showed seasonal fluctuation, but did not vary with sex. Total lipid concentrations in the plasma of both males (17.7 ± 0.61 mg ml^–1) and females (14.1 ± 0.64 mg ml^–1) showed seasonal fluctuations with the lowest levels in late Spring during spawning. Plasma lipids in females were significantly (p < 0.0001) lower than those of the males except during early ovarian secondary growth. Analysis of the lipid class composition revealed that the decrease in plasma lipid concentrations in females prior to spawning is primarily due to a decrease of up to 50% in the phospholipid content of the plasma relative to males. Striped bass vitellogenin was found to contain approximately 20% lipid by weight with nearly 80% of the lipid being phosphatidyl choline (PC). Vitellogenin levels previously measured in these individuals were highest during the winter months and decreased in the 2 months prior to spawning. Although mature striped bass oocytes are rich in wax esters, no wax esters or fatty alcohols were found in the plasma. Analysis of the fatty acyl composition of separated lipid classes suggests that PC is the primary carrier of the essential (n=3) fatty acids 22:6 (DHA) and 20:5 (EPA) to the gonads. Fatty acid analysis of the lipids associated with vitellogenin revealed that levels of essential fatty acids were low relative to vitellogenin-borne lipids from other teleosts. The lack of detectable wax esters in plasma lipids of female striped bass suggests that these abundant lipids in mature eggs are synthesized within the oocytes.     

Effect of broodstock diets on lipid classes and their fatty acid composition in eggs of gilthead sea bream (Sparus aurata L.)

Total lipid content, total lipid fatty acids, lipid classes and their fatty acid compositions were studied in eggs of gilthead sea bream from two different broodstocks. The two broodstock diets used had the same total lipid content, but differed with respect to their fatty acid levels. The lipid class composition of eggs from different origins was not significantly different. The predominant polar lipids were phosphatidylcholine, phosphatidylethanolamine and sphingomyelin, and the main neutral lipid classes were cholesterol esters and triacylglycerols. The fatty acid composition of total lipids and main lipid classes in the two groups of eggs showed marked differences, reflecting the influence of fatty acid levels in the broodstock diets.     

Physical and biochemical properties of effluent leaving an onshore Atlantic cod (Gadus morhua,Linnaeus 1758; Gadiformes: Gadidae) aquaculture facility and potential use in integrated multi‐trophic aquaculture

The physical and biochemical properties of Atlantic cod (Gadus morhua) wastes were analysed, and the waste remediation potential of blue mussels (Mytilus edulis) was assessed. Waste generated daily by Atlantic cod represented 24.9% of the cod feed added to the system. Particle distributions determined using a Coulter Multisizer and image analysis revealed that the majority of the particles in terms of numbers occupy the smaller size ranges; however, larger particles occupy a larger proportion of the volume. Effluent was composed of particles <70 μm (36%), 70–500 μm (31%) and particles >500 μm (33%) by weight. The amount of dissolved carbon and nitrogen associated with the effluent represented 3.1% and 3.7%, respectively, of the total feed added to the system daily. Particles <70 μm had significantly less organic matter, lipids and fatty acids and were expected to be ingested more by mussels than larger particles. The major lipid classes present in effluent were free fatty acids, triacylglycerols, phospholipids, acetone mobile polar lipids and sterol. Cod effluent contained two essential fatty acids DHA and EPA, a diatom marker (16:1ω7), as well as two zooplankton markers 22:1ω11 and 20:1ω9, which accumulated in mussels and may serve as markers for aquaculture wastes. Although only 36% of the effluent was of a size suitable for mussel ingestion, this size fraction has the greatest potential to spread to surrounding areas. These particulates may be useful as an alternate food source when natural seston is low.     

A study of the arachidonic acid requirements of the giant tiger prawn, Penaues monodon

This study examined the dietary requirement of arachidonic acid (ARA) when that of linoleic acid (LOA), the natural precursor to ARA, was also satisfied with linolenic acid (LNA) and also with and without the other key dietary highly unsaturated fatty acids (HUFA). Growth by prawns fed diets supplemented with ARA was poorer than in diets where it was not present. Supplementation of ARA to diets with either optimized HUFA or just optimised poly unsaurated fatty acids (PUFA) (i.e. LOA, LNA) resulted in poorer growth. Growth was poorest by prawns (215 ± 13%) fed diets with ARA supplemented at 20% of the total fatty acids but including 7% LOA, 21% LNA and 4% of both eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Growth was best in prawns fed diets devoid of ARA but with 7% LOA and 21% LNA (350 ± 19%). Prawns fed the reference diet (348 ± 21%) and the other diet devoid of ARA but containing about 7% LOA, 21% LNA and 4% of both EPA and DHA (345 ± 18%) had similar growth. The growth responses were not effects of altered lipid or fatty acid digestibilities. Indeed supplementation of ARA to the diet marginally improved the digestibility of the total neutral lipid in the diet and the digestibilities of some other dietary fatty acids. The amount of lipid in the digestive glands of prawns fed with the diets was reduced by the inclusion of ARA in the dietary lipids. Composition of the lipids in the digestive gland (DG) of the prawns was almost directly related to the composition of their dietary lipids. The proportion of ARA in the total fatty acids increased with level of supplementation of dietary ARA. An increased level of dietary ARA reduced the proportion of EPA, DHA in the DG lipid and also the total n‐3 and n‐6 fatty acids in the DG lipid. The results of this study support that addition of ARA to the diet of Penaues monodon when the other key essential fatty acids (EFA) have been optimized, does not improve their growth performance. It is suggested that key cause for this response may lie in the importance of the balance of the n‐3 to n‐6 fatty acids in the diet of these animals.     

Ontogeny of schooling behavior in the oval squid <Emphasis Type="Italic">Sepioteuthis lessoniana</Emphasis>

In contrast to schooling behavior in fish, which is well documented, the schooling behavior of an evolutionary counterpart, squid, has not been adequately described in the literature. In the current study, we investigated the ontogeny of schooling behavior in the oval squid Sepioteuthis lessoniana reared from hatching to about two months of age. During the two months of development, the distance and angle between nearest-neighbor individuals decreased from 5.3 mantle lengths (ML) to 1.8 ML and from 42.7° to 24.2°, respectively. In addition, the swimming distance of individuals in experimental duration decreased from 530.4 to 79.9 ML, and the relative swimming speed also decreased from 17.1 to 4.6 ML/s during the same period, with increasing synchronized hovering of individuals. These observations clearly suggest that oval squid swim randomly until 20 days after hatching, then form a school 30–60 days after hatching with an inter-individual distance of 2.0 ML. At two months after hatching, oval squid individuals swam in a parallel orientation and formed a belt-shaped arrangement, similar to the adult schooling behavior observed in natural populations.     

Abundance and origins of plasma lipids in sexually maturing female coho salmon Oncorhynchus kisutch (Walbaum) in culture

Coho salmon Oncorhynchus kisutch are semelparous spawners with highly synchronized oocyte growth. Plasma was collected from maturing female fish and plasma lipids were quantified by lipoprotein class. Stable ¹³C isotopes were employed to investigate the origins of plasma lipids. Plasma lipoproteins were partitioned into the very low density (VLDL), low density (LDL), high density (HDL) and very high density (VHDL) lipoprotein classes. Lipids from all lipoprotein classes increased between the lipid droplet and early vitellogenesis stages of oocyte growth and VHDL lipids continued to increase through mid vitellogenesis (P < 0.05). During vitellogenesis, total plasma lipid concentrations were similar to the sum of lipoprotein lipids (P = 0.51). Plasma vitellogenin determined by an ELISA method was very well correlated with VHDL lipid during vitellogenesis (R² = 0.91, n = 15). In general, the δ¹³C values of plasma lipids reflected that of feed (exogenous) and muscle (endogenous) lipids when feed and muscle δ¹³C values were similar, and were intermediate when differences existed between the two lipid sources. With one exception, the δ¹³C values of lipids from all lipoprotein classes within a plasma sample were similar. Results indicate that during sexual maturity, lipids from all plasma lipoprotein classes originate from a common pool of exogenous and endogenous lipids.     

The dietary linoleic and linolenic fatty acids requirements of the prawn Penaeus monodon

The dietary requirement of the prawn Penaeus monodon for linoleic (LOA) and linolenic (LNA) fatty acids was examined in the absence of other long-chain polyunsaturated and highly unsaturated fatty acids (PUFA-20:2, 20:3, 22:2, 22:3 and HUFA-18:4, 20:4, 20:5, 22:4, 22:5, 22:6, respectively). Incremented dietary amounts of LOA (7, 14, 21, 28 and 35% of total fatty acids) and LNA (0, 7, 14, 21 and 28% of total fatty acids) were examined in a 5 × 5 factorial growth experiment lasting 50 days. An additional diet containing both PUFA and HUFA (cod-liver oil) was provided as a reference. The total lipid content (excluding sterols) of each of the 26 diets was maintained at 70 g kg⁻¹ of dry diet. The fatty acid composition of the neutral lipid was manipulated by blending different plant oils and supplementing with purified free fatty acids to provide the desired fatty acid composition upon addition to the total diet. At the end of the 50-day growth experiment, the prawn digestive gland (DG) was quantitatively analysed for lipid and fatty acid content. Prawns fed the reference diet increased in weight (mean ± SEM) by 214 ± 6%. Growth was generally greater when combinations of LOA and LNA were used. The best growth (213 ± 17%) was obtained with the diet containing a fatty acid content of 14% LOA and 21% LNA. This growth was comparable to that of the reference diet. The digestibility of the total lipid in the diet was usually higher when both fatty acids were present. The lipid content of the DG was highest in prawns fed diets containing both LOA and LNA, similar to the growth response. The fatty acid composition of the prawn's DG lipid reflected the fatty acid composition of the diet. However, the maximum assimilation of LNA in the DG lipid (14.2% of DG lipid fatty acids) was about half that of LOA (32.5% of DG lipid fatty acids).     

Fasting and refeeding lead to more efficient growth in lean pacu (Piaractus mesopotamicus)

We evaluated whether body fat content affects the energetic metabolism and growth in pacu submitted to daily feeding, fasting and refeeding. For 15 days, fish were fed different diets to obtain lean and fat conditions, and then subjected, for 20 days to: (1) continuously feeding (control), or (2) fasting for 15 days and refeeding for 5 days. Blood (glucose, triglycerides, cholesterol, non‐esterified fatty acids and total protein) and tissue (liver lipid and glycogen, muscle lipid and mesenteric fat) metabolic indicators, and growth performance parameters (weight gain, specific growth rate, daily feed intake and feed conversion ratio) were measured. Fasting led both lean and fat pacu to make notable use of their energy reserves, through glycogenolysis and lipolysis, reflected in reduced blood glucose and triglycerides, liver glycogen and muscle lipid levels. Lipolysis was confirmed by the high levels of non‐esterified fatty acids, especially in fat pacu. Refeeding led to higher plasma glucose and liver lipid in lean fish. Muscle fat increased in fat fish but was not restored in lean fish, while mesenteric fat index (MFI) remained the same in fat fish and increased in lean fish. Although refeeding occurred only for 5 days, lean fish grew more and were more efficient at utilizing food (higher weight gain and better feed conversion ratio). In conclusion, our results suggest that fat pacu have higher glycogenic and lipogenic abilities, and the higher deposition of lipids in fish does not mean higher availability of energy for growth when compensatory growth is stimulated by refeeding after fasting.     

Relationship between dietary phospholipid classes and neutral lipid absorption in newly-weaned turbot, shape Scophthalmus maximus

A 28-day feeding trial was conducted for comparing the effect of different dietary phospholipid (PL) classes on the growth of post-larval turbot and on the incorporation of dietary neutral lipid fatty acids into their body lipids. Prior to the experiment the turbot were weaned for one week on a PL-free diet. The nine experimental diets were isolipidic and contained an equal amount of highly unsaturated fatty acids in the form of ethyl esters. They differed by their PL content (0, 1 or 2%) and by the PL class composition of the added soybean PL fractions.Compared to the PL-free diet, diets enriched with phosphatidylcholine (PC) resulted in a better growth, a higher triglyceride content (% body dry matter) and increased levels of docosahexaenoic acid (% total fatty acids) in each of the examined body lipid classes (neutral lipid, phosphatidylcholine, phosphatidylethanolamine and phosphatidylinositol). The effects of the other soybean PL fractions were less explicit than those noted for soybean PC.The results support the idea that dietary PC plays a role in the intestinal absorption of neutral lipid fatty acids. This might, at least partially, explain the superiority of PC for enhancing growth. Abbreviations: DHA – docosahexaenoic acid (22:6n-3); EPA – eicosapentaenoic acid (20:5n-3); HUFA – highly unsaturated fatty acid; PA – phosphatidic acid; PC – phosphatidylcholine; PE – phosphatidylethanolamine; PI – phosphatidylinositol; PL – phospholipid; PS – phosphatidylserine; PUFA – polyunsaturated fatty acid.     

Effect of dietary astaxanthin on the growth performance,lipid composition and post-mortem skin colouration of red porgy <Emphasis Type="Italic">Pagrus pagrus</Emphasis>

A 120-day feeding trial was conducted to assess the possible effect of including dietary astaxanthin (ASTX), for different lengths of time prior to harvest, on red porgy growth performance, lipid and fatty acid composition and post-mortem skin colour. Four treatment groups were established with fish of initial weight of approximately 220 g. Control group was fed on a control diet (with no astaxanthin included) for the entire experiment. ASTX60 group was fed for the first 60 days of the trial on the control diet and 60 days before harvest on a diet with 100 mg of unesterified astaxanthin per kg⁻¹ of diet (ASTX diet). ASTX90 group was fed for the first 30 days of the trial on control diet and 90 days before harvest on ASTX diet. ASTX120 group was fed on ASTX diet during the complete experiment. Results showed an enhancement of certain growth parameters due to ASTX diet and feeding period. In addition, a lipid-lowering effect on whole fish and liver was observed with increased feeding time with ASTX diet, as well as a significant variation of liver and head kidney fatty acid profiles. Concerning skin colouration, only ASTX90 and ASTX120 treatment groups presented adequate hue values throughout the 7 days post-mortem, similar to those reported for wild red porgy. However, skin chroma was close to wild specimens in ASTX120 treatment fish only and up to day three post-mortem. Skin lightness (L*) was not affected by astaxanthin inclusion. Feeding red porgy for a period of 90–120 days before harvest on ASTX diet seems to affect red porgy growth performance, lipid content and fatty acid profile. However, to achieve an adequate skin colouration, throughout a post-mortem period of 7 days, ASTX diet should be given 120 days before harvest.     

Effect of diet on the lipid composition of the commercial clam Donax trunculus (Mollusca: bivalvia): sex‐related differences

This paper describes the lipid composition of the commercial bivalve Donax trunculus and the differences originated when the animals were fed with two phytoplankton species (Tetraselmis suecica and Chaetoceros sp.) in a hatchery. We also analysed sex‐related differences in lipid classes and fatty acid profile. Total lipids were higher in females than in males. Triglycerides and phospholipids were the major lipid components, and the former dominated in females and the latter in males. The main fatty acids in both sexes were 16:0, 20:5n‐3 (eicosapentaenoic acid) and 22:6n‐3 (docosahexaenoic acid). Females showed higher percentages of saturated and monounsaturated fatty acids and lower levels of polyunsaturated fatty acids than males. Significant differences in total lipid, lipid classes and fatty acid profiles were also found due to diet. Docosahexaenoic acid decreased and total lipids, free fatty acids, arachidonic acid and EPA increased in both sexes. Despite these differences, the condition of the species was maintained and the broodstock even maturated.     

You are what you eat? Differences in lipid composition of cod larvae reared on natural zooplankton and enriched rotifers

A laboratory experiment with larval cod fed natural zooplankton and enriched rotifers was carried out to investigate the effects of feed type on fatty acid (FA) and lipid composition. A divergence in FA composition was observed within a week of feeding on respective diets, and subsequent transfers of larvae from one feeding regime to the other also confirmed a rapid change in FA composition towards that of the newly provided feed source. The rapid change in FA composition after switching diet is in part expected to be due to the high growth and tissue turnover of cod larvae during the early life stages and provides an opportunity to assess recent feeding history by means of FA analysis. The FA contents also varied between the main analysed lipid classes, with relatively higher eicosapentaenoic acid levels in neutral lipids than in polar lipid classes. Although zooplankton contained notably more polar lipids and less neutral lipids than enriched rotifers, the relative amounts of polar and neutral lipids in larvae from respective prey groups were similar, signifying that the larval composition only partly reflects what they have been eating. Still, the FA composition of the previous diet was still discernible in larvae after 1–2 weeks of transfer to a new diet or after weaning to a formulated feed. The potential long‐term effects of these nutritional differences are discussed.     

Atlantic salmon, Salmo salar, utilizes wax ester-rich oil from Calanus finmarchicus effectively

Against a background of decreasing availability of fish oils for use in aquaculture, the present study was undertaken to examine whether a wax ester-rich oil derived from the calanoid copepod Calanus finmarchicus, could be used effectively by Atlantic salmon when supplied in their diet. Individually tagged Atlantic salmon of initial weight around 500 g were divided into replicate tanks of two dietary groups and fed either a fish oil supplemented diet, or an experimental diet coated with Calanus oil. Wax esters accounted for 37.5% of the lipids in the Calanus oil diet but were absent from the fish oil diet in which triacylglycerols (TAG) were the major lipid class. Over the feeding period (140 days) the salmon fed fish oil displayed a greater increase in length, but there was no significant difference between the two groups in weight gained. The specific growth rates (0.75) and the feed conversion ratio of fish fed the two diets were similar throughout the study. No differences were observed in the apparent digestibility coefficients (ADC) of fish fed Calanus oil or fish oil. The ADC of fatty acids decreased with chain length and increased with unsaturation. Long-chain alcohol utilization showed a similar tendency although there was a notable difference in that saturated long-chain alcohols were utilized better than the comparable fatty acid homologue. In fecal lipid of fish fed Calanus oil, the content of 16:0 alcohol decreased in both the free long-chain alcohol and wax ester fractions, while the corresponding fatty acid increased in the feces of both dietary groups of fish. In contrast, the proportion of the 22:1n−11 alcohol increased in both fecal wax esters and free long-chain alcohol fractions whereas 22:1n−11 fatty acid displayed no accumulation. The observed patterns of fatty acid and long-chain alcohol compositions in fecal lipid compared to those of the initial dietary lipid are consistent with the digestive lipases of salmon preferentially hydrolyzing esters containing polyunsaturated fatty acid (PUFA) moieties. The wax esters of Calanus oil contained substantial amounts of the n−3 PUFA, 20:5n−3 and 22:6n−3, that were effectively deposited in muscle and liver tissues. No major differences were seen in either lipid content/lipid classes or in gross fatty acid composition of these tissues between the two dietary groups. It is concluded that that Atlantic salmon in seawater can effectively utilize diets in which a major lipid component is derived from zooplankton rich in wax ester without any detrimental change in growth or body lipid composition. This finding gives support to the use of lipid from zooplankton from high latitudes as an alternative or as a supplement to fish oil and a provider of long-chain n−3 PUFA in diets for use in salmon aquaculture.     

Dietary fish oil replacement with lard and soybean oil affects triacylglycerol and phospholipid muscle and liver docosahexaenoic acid content but not in the brain and eyes of surubim juveniles Pseudoplatystoma sp.

Triplicate groups of juvenile suribim were fed for 183 days one of four different isonitrogenous (47.6% crude protein) and isolipidic (18.7% lipid) diets formulated using three different lipid sources: 100% fish oil (FO, diet 1); 100% pig lard (L, diet 2); 100% soybean oil (SO, diet 3), and FO/L/SO (1:1:1, w/w/w; diet 4). The tissue levels of fatty acids 18:2n − 6 and 18:3n − 3 decreased relative to corresponding dietary fatty acid values. The 20:5n − 3 and 22:6n − 3 composition of muscle and liver neutral lipids were linearly correlated with corresponding dietary fatty acid composition. In contrast, the 22:6n − 3 composition of the brain and eye were similar among treatments. The 22:6n − 3 level was enriched in all tissues, particularly in the neural tissues. Similar results were observed for tissue polar lipids: fatty acids content reflected dietary composition, with the exception of the 22:6n − 3 level, which showed enrichment and no differences between groups. Given these results, the importance of the biochemical functions (transport and/or metabolism) of 22:6n − 3 in the development of the neural system of surubim warrants further investigation. M.D. Noffs and R.C. Martino dedicate this study to the memory of Prof. Dr. Luiz Carlos Trugo.     

Effects of dietary n‐3 to n‐6 fatty acid ratios on spawning performance and larval quality in tongue sole Cynoglossus semilaevis

This study investigated the effect of n‐3 to n‐6 fatty acid ratios in broodstock diets on reproduction performance, fatty acid composition of eggs and gonads of tongue sole Cynoglossus semilaevis. Broodstock were fed five isonitrogenous and isoenergetic diets for 60 days. The supplemented lipids were prepared by a combination of fish oil and soybean oil inclusion FO (fish oil); FSO1 (fish oil: soybean oil = 7:1); FSO2 (fish oil: soybean oil = 2.2:1); FSO3 (fish oil: soybean oil = 1:1); FSO4 (fish oil: soybean oil = 1:4.3) as lipid sources with different n‐3 to n‐6 fatty acid ratios 10.40, 5.21, 2.81, 1.71 and 0.87. Results showed that relative fecundity, fertilization rate and survival rate of larvae at 7 days posthatching were all higher in broodstock fed FSO1 and FSO2 diet and significantly (P < 0.05) decreased in groups fed FSO3 and FSO4 diets. The best result in starvation tolerance test was obtained in FSO2 diet. The present study suggests that n‐3 and n‐6 PUFA ratio in broodstock diet has a considerable effect on spawning performance, egg and larval quality for C. semilaevis.