Changes in mitochondrial fatty acid composition following temperature acclimation of carp and their possible effects on FoF1-ATPase activity

Carp undergo temperature acclimation of respiratory function by altering mitochondrial ATP synthase (F_oF₁-ATPase) both quantitatively and qualitatively (Itoi et al. 2003). To address such acclimation temperature-dependent changes of F_oF₁-ATPase activity, we investigated in this study the correlation between the fatty acid composition and F_oF₁-ATPase activity in fast muscle of thermally acclimated carp. The quantities of saturated fatty acids of mitochondria from carp acclimated to 10 °C were significantly lower than those of carp acclimated to 30 °C. While mono- and poly-unsaturated fatty acids tended to increase with cold acclimation of carp, the molar concentration of 16:0 aldehyde in mitochondria from the 10 °C-acclimated carp were less than those from the 30 °C-acclimated fish. The specific activities of F_oF₁-ATPase in the 10 °C- and 30 °C-acclimated fish mitochondria were calculated to be 167±22 and 56±10 nmol/min ⋅ mg mitochondrial protein, respectively, the difference being significant at P<0.005. Taken together, the increase in F_oF₁-ATPase activity in fast muscle mitochondria of carp after cold temperature acclimation may be closely related to the increase of unsaturated fatty acids in mitochondria. Abbreviations: BSA - bovine serum albumin; DHA - docosahexaenoic acid; EGTA - ethyleneglycol bis(2-aminoethylether)tetraacetic acid; EPA - eicosapentaenoic acid; F_oF₁-ATPase - mitochondrial ATP synthase; α-F₁-ATPase - F_oF₁-ATPase α-subunit; β-F₁-ATPase - F_oF₁-ATPase β-subunit; HEPES - 2-[4-(2-hydroxyethyl)-1-piperazinyl]ethanesulfonic acid; SDS - sodium dodecyl sulfate; SDS-PAGE - SDS-polyacrylamide gel electrophoresis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effects of thermal acclimation on tissue fatty acid composition of freshwater alewives (Alosa pseudoharengus)

In this study, we examine changes in fatty acid composition of polar and neutral lipids in gill, liver, and muscle of freshwater alewives (Alosa pseudoharengus) after temperature challenges in the laboratory. Alewives experienced either a warm or cold challenge in which temperatures were raised or lowered 0.5°C day⁻¹ over 4–6 weeks. In alewives experiencing the cold challenge, gill polar lipids showed evidence of significant remodeling, including decreases in palmitic acid and saturated fatty acids and increases in n-3 and n-6 highly unsaturated fatty acids including docosahexaenoic acid (DHA) and arachidonic acid. In alewives experiencing the warm challenge, we observed significant increases in saturated fatty acids (due mainly to increased palmitic acid) and decreases in polyunsaturated fatty acids in polar lipids of muscle and liver tissue. Fish that died during the cold challenge had significantly higher levels of palmitic acid in muscle polar lipids compared to fish that survived; fish that died during the warm challenge displayed complex changes in fatty acid composition. Based on theoretical considerations, the changes in polar lipids we observed during thermal acclimation are likely to promote appropriate membrane fluidity under each thermal regime. The increased incorporation of highly unsaturated fatty acids during cold acclimation could have significant physiological and ecological implications. In particular, since highly unsaturated fatty acids are typically scarce in freshwater food webs, dietary deficiencies in these essential fatty acids may be a significant factor in winter mortality of freshwater alewives.     

Seawater acclimation of tilapia, Oreochromis spilurus spilurus Günter, fry and fingerlings

The effect of size and acclimation period to full-strength sea water was investigated using the mortality, growth, chloride cell proliferation and plasma Na concentration in four size groups (0.03-1.6 g mean initial weight) of mixed-parentage, sex-reversed, all-male fry and fingerlings of Oreochromis spilurus spilurus Günter obtained from University of Stirling. The fish were transferred from fresh water to sea water (36.6%₀) through a continuous salinity increase during a 48, 72 or 120 h acclimation period. Survival was high in all groups, although the smallest fish (0.03 g) showed significantly higher mortality than the larger fish. The acclimation regime had no effect on growth rate, but 120 h acclimation gave highest final weight in the newly released group. Regardless of acclimation period, size and plasma Na concentration during the acclimation period, the plasma Na level stabilized within 12 h after full salinity in the two largest size groups. Ovoid voluminous chloride cells proliferated in all groups during the acclimation period, and numbers stabilized with stable salinity. It is concluded in this study that O. spilurus spilurus can successfully be acclimated to sea water with a gradual continuous acclimation period of 48 h, even as newly released fry (0.03 g). However, an acclimation period of 120 h gave the highest final weight for this size group.     

Enrichment of C20-22 Polyunsaturated Fatty Acids from Refined Liver Oil of Leafscale Gulper Shark,Centrophorus squamosus

The C_20-22 polyunsaturated fatty acids (C_20-22 PUFAs), mainly eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3), were concentrated from the refined liver oil of deep sea leafscale gulper shark, Centrophorus squamosus, by sequential processes of winterization, urea complexation, and argentation chromatography. Winterization at 4°C using acetonitrile as solvent showed significant reduction of the total saturated fatty acid content (12%) with a concomitant increase of polyunsaturated fatty acids (36.3%). The urea complexation process significantly enriched the total polyunsaturated fatty acids (49.5%), with a reduction in saturated fatty acids (83.9%). Silica gel based argentation chromatography further concentrated the esters of C_20-22 PUFA (>99 percent purity). Nuclear Magnetic Resonance spectroscopy was used as a chemical fingerprinting tool to study the enrichment of C_20-22 PUFAs at various stages of the purification process. An increase in the proton signal intensity at the olefinic region (at δ 4–6) and a decrease in the aliphatic signals (at δ 0.5–2) showed that the process successfully enriched the C_20-22 PUFAs.

Abbreviations: PUFA, polyunsaturated fatty acid; EPA, eicosapentaenoic acid; DHA, docosahexaenoic acid; FAME, fatty acid methyl esters; SFA, saturated fatty acid; MUFA, monounsaturated fatty acid; NMR, nuclear magnetic resonance; GCMS, gas chromatography mass spectrometry; FFA, free fatty acid.     

养殖博氏鱼芒肉营养成分的分析及评价

采用国家标准方法测定湖北英山博氏(鱼芒)肉一般营养成分、氨基酸、脂肪酸和矿物质元素含量.结果表明,博氏(鱼芒)肉中水分、粗蛋白、粗脂肪和粗灰分的含量分别为75.36％±1.07％、17.90％±0.43％、5.13％±0.18％和0.98％±0.09％;18种氨基酸总量为(69.01±0.07) g/100 g(干重),其中5种鲜味氨基酸占氨基酸总量的41.70％,8种人体必需氨基酸占氨基酸总量的48.68％,必需氨基酸与非必需氨基酸比值为95.06％;粗脂肪中含24种脂肪酸,油酸含量38.41％±0.29％最高,单不饱和脂肪酸含量占脂肪酸总量的42.68％±0.10％,n-6多不饱和脂肪酸与n-3多不饱和脂肪酸的比值为1.48;矿物质元素中钾含量最高,为(1 118.51±30.67) mg/100 g(干重),微量元素中,铁、锌含量最高,分别为(1.19±0.10)和(1.18±0.05)mg/100 g(干重).与其它鱼类相比,博氏(鱼芒)肉蛋白质质量较高,氨基酸组成比例均衡,富含n-3多不饱和脂肪酸,矿物质元素含量丰富,有较高的营养价值.     

Effect of environmental factors on the fatty acid profiles and physicochemical composition of oysters (Crassostrea gasar) in Amazon estuarine farming

The objective of this study was to evaluate the effect of environmental factors on the fatty acid profiles and physicochemical composition of Crassostrea gasar cultured in two locations with differences in salinity and precipitation gradients. The study period was divided into four seasonal divisions—the rainy–dry transition period, the dry season, dry–rainy transition and the rainy season. The salinity, pH and temperature were measured at each site during specimen collection. A total of 712 oyster samples were used for fatty acid profiling and physicochemical analysis. Salinity and precipitation were the environmental parameters that influenced the fatty acid profile and physicochemical characteristics of oysters. C. gasar exhibited excellent values of n3 polyunsaturated fatty acids (DHA, EPA and eicosatrienoic), with a predominance of these acids during periods of higher precipitation. Variations in precipitation and salinity resulted in significant differences in oyster nutritional characteristics. Oysters grown in Amazonian estuaries can be considered nutritious throughout the year, with better conditions during the rainy season.     

Growth and performance of the whiteleg shrimp Penaeus vannamei (Boone) cultured in low‐salinity water with different stocking densities and acclimation times

We evaluated the performance of whiteleg shrimp Penaeus vannamei (Boone, 1931) in response to different stocking densities and acclimation periods. Shrimp postlarvae were acclimated from seawater (30 g L^?1) to low‐salinity well water (<1.0 g L^?1) at a constant hourly reduction rate of 40, 60, 80 and 100 h. After acclimation to low‐salinity well water, postlarvae from each acclimation time treatment were stocked in three replicate tanks at densities of 50, 100, 150 or 200 shrimps m^?2 for 12 weeks of growth. Salinity averaged <1.0 g L^?1 for each growth study. The different treatments resulted in significant differences in both the final body weight and the survival rate (SR). Shrimp acclimated for 100 h showed substantially improved survival (83%) relative to shrimp acclimated for shorter periods. Shrimp yields for all cultured periods ranged from 0.32 kg m^?2 in tanks stocked at 50 m^?2 to 1.14 kg m^?2 in tanks stocked at 200 m^?2. We conclude that whiteleg shrimp can be successfully grown in low‐salinity well water, and that the growth, production output and SRs are significantly higher when shrimp are acclimated for longer periods.     

The effects of freshwater rearing on the whole body and muscle tissue fatty acid profile of the European sea bass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>)

The purpose of this study was to investigate the effect of freshwater rearing on the fatty acid profiles of the whole body and muscle tissue of the European sea bass (Dicentrarchus labrax). Half of initial fish were gradually acclimated to freshwater (FW) kept at the same temperature to salt water and grown in same conditions as their counterparts in saltwater (SW). The decrease in salinity caused an increase in the percentages of 18:1n − 9, 24:1n − 9, 18:3n − 3, 18:2n − 6 and decrease in the percentages of 14:0, 15:0, 20:0, 21:0, 20:5n − 3 and 22:6n − 3 both in the whole body and in the muscle tissue fatty acid profiles. The lipids of FW-reared fish contained significantly (P < 0.01) higher percentages of 18:2n − 6 and 18:3n − 6 than that of SW-reared fish. However, percentages of 20:5n − 3 and 22:6n − 3 fatty acids decreased significantly (P < 0.05) compared with those of salt water-reared European sea bass. There was a clear trend of decrement in the percentages of n − 3 PUFA fatty acids due to the decrease in water salinity. However, the percentages of n − 6 PUFA fatty acids were also increased with the decrease in water salinity. We concluded that the FW acclimation is followed by changes in certain lipid classes of sea bass muscle tissue and whole body samples. n − 3/n − 6 PUFA ratios were characteristic to previously reported ratios for both FW- and SW-reared European sea bass. In addition, EPA/DHA ratios were basically similar for the fish reared in both SW and FW indicating the equal nutritional value of the final products in terms of providing PUFA’s for human nutrition.     

The effects of temperature on the uptake and metabolism of benzo[a]pyrene in isolated gill cells of the gulf toadfish,Opsanus beta

The effects of acclimation temperature and acute temperature change on the uptake and metabolism of the procarcinogen benzo[a]pyrene (BaP) by gill cells of the gulf toadfish, Opsanus beta, were examined. BaP was rapidly accumulated by isolated gill cells and uptake rates were directly proportional to BaP concentration in the medium (1 to 100 μg/ml). Uptake rates were higher in cells isolated from fish acclimated to 18°C when compared to cells from 28°C acclimated fish at all incubation temperatures. When cells were exposed to BaP at the respective acclimation temperatures of the fish, uptake rates were similar (0.14 ± 0.01 at 18°C and 0.12 ± 0.01 μg BaP/s/10 mg cells at 28°C). This finding is discussed in view of results which showed a partial compensation of membrane fluidity in plasma membranes isolated from fish from the two acclimation temperatures. At higher incubation temperatures, cells from fish acclimated to 18°C metabolized BaP at a greater rate than those at 28°C (49.6 ± 1.92 and 43.0 ± 2.24 μg/g/8h, respectively, at 23°C). Low but detectable activities of common biotransformation enzymes (aryl hydrocarbon hydroxylase, glutathione-S-transferase) and cytochrome P-450 content were found, however, no significant differences were evident between cells from fish acclimated to different temperatures. To whom to address correspondence     

Dynamics of total lipids and fatty acids during embryogenesis and larval development of Eurasian perch (Perca fluviatilis)

Total lipid and fatty acid compositions were determined during embryogenesis and larval development in Eurasian perch (Perca fluviatilis). During embryonic development, perch did not catabolize lipids and fatty acids as an energy source. However, during larval development, there was an exponential relationship between the decrease in total lipids and the duration of starving (r ²=0.9957) and feeding (r ²=1). The duration of the starving period (10 days post hatching) was shorter than the feeding period (35 days post hatching). In both starved and fed larvae, there is an apparent preference in utilization of polyunsaturated fatty acids followed by monounsaturated fatty acids. Saturated fatty acids were utilized by neither fed perch larvae nor by starved perch larvae. In starved larvae, palmitoleic 16:1(n-7) and oleic 18:1(n-9) acids were the preferentially monounsaturated fatty acids catabolized and their contribution as energy source from total fatty acids catabolized over the first week was 37.6%. In fed larvae, these 2 nutrients were also the most monounsaturated fatty acids utilized as energy source and possibly also as precursors for others monounsaturated fatty acids biosynthesis. During the same period and among (n-6) polyunsaturated fatty acids, starved perch utilized less linoleic 18:2(n-6) and arachidonic 20:4(n-6) acids than fed larvae despite the fact that the starved perch were in more unfavorable nutritional conditions. In the case of (n-3) fatty acids, starved larvae utilized more linolenic acid 18:3(n-3) and less eicosapentaenoic 20:5(n-3) acid and docosahexaenoic 22:6(n-3) acid than fed perch. Starved larvae probably spared 20:5(n-3) and 22:6(n-3) for physiological functions.     

Growth performance,osmoregulatory and metabolic modifications in red porgy fry,Pagrus pagrus,under different environmental salinities and stocking densities

The effects of two different environmental salinities [brackish water (BW), 12‰; sea water (SW), 39‰] and initial stock densities [low (LD), 1.0 g L^?1; high (HD), 2.0 g L^?1] on growth, osmoregulation, stress and energy metabolism of the fry Pagrus pagrus were investigated over a period of 45 days. Pagrus pagrus (n=80, 5.51 ± 0.25 g mean initial body weight) were randomly divided in eight groups. Growth, weight gain and specific growth rate increased in BW‐acclimated fish compared with SW‐acclimated fish. No differences were observed between the two stock densities tested at either environmental salinity. Plasma osmolality was lowest in BW‐acclimated specimens, but the stock density had no effect on this parameter. Branchial Na⁺,K⁺‐ATPase activity was positively correlated with environmental salinity, but unaltered at the renal level. Plasmatic parameters were enhanced by salinity and stocking conditions. At the hepatic level, triglyceride values were enhanced in BW‐acclimated fish maintained at LD. Muscle metabolites (glycogen, glucose and lactate) increased in BW‐ compared with SW‐acclimated fish; stock density had no influence. Our data suggest that changes in metabolic parameters could be correlated with the higher growth rates observed in P. pagrus acclimated to BW, while no significant effects due to the stocking density used were observed.     

Nucleic acids and fatty acids of the common octopus, Octopus vulgaris, in relation to the growth rate

The aim of this study was to investigate changes in the ribonucleic acid (RNA)/deoxyribonucleic acid (DNA) ratio and the fatty acid composition of cultured Octopus vulgaris (50–750 g) in relation to recent (last 30 days) specific growth rate (SGR). Wild animals (80–500 g), collected in the field throughout the year (Aegean Sea, Mediterranean), were also examined for the aforementioned biochemical parameters. Octopuses were reared in a closed seawater system at three different temperatures (15, 20 and 25 °C). The octopuses were fed on squid (Loligo vulgaris). The cultured animals showed a high n‐3 (33–52.9%) and n‐6 (3.3–13.7%) polyunsaturated fatty acid content, but with a high variation for 22:6n‐3 [docosahexaenoic acid (DHA)], 20:5n‐3 [eicosapentaenoic acid (EPA)] and 20:4n‐6 [arachidonic acid (AA)]. The proportion of these fatty acids (% total fatty acids) and the RNA/DNA ratio were linearly (P<0.0001) related to SGR. Specifically, RNA/DNA (0.5–1.9) and AA (2.7–10.7%) increased, while EPA (10.4–19.7%) and DHA (20.8–31.9%) decreased, with increasing SGR (0.4–1.7% day⁻¹). The highest levels of SGR, RNA/DNA and AA were detected in small (50–150 g) octopuses reared at 20 and 25 °C and in large (500–750 g) animals reared at 15 °C. Similar RNA/DNA levels and fatty acid percentages were found in wild octopuses. It is concluded that RNA/DNA, DHA, EPA and AA could be used as biochemical indices for predicting the growth rate of O. vulgaris.     

Effects of salinity on the fatty acid compositions of total lipid and individual glycerophospholipid classes of Atlantic salmon (Salmo salar) and turbot (Scophthalmus maximus) cells in culture

Cells from a relatively stenohaline marine species, turbot (Scophthalmus maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce OPs varying from 300 to 500 mOsm kg^–1 and the direct effects of OP (salinity) on the fatty acid compositions of the main glycerophospholipid classes were determined. The most dramatic effects of salinity on total lipid fatty acids were observed in polyunsaturated fatty acids (PUFA) in TF cells. There was a graded decrease in the percentage of 18:2n-9, and consequently total n-9 PUFA, and concomitantly increased percentages of both total n-3 and n-6 PUFA with increasing salinity. The increased n-3 and n-6 PUFA was due to significantly increased percentages of the major fatty acids in each of these groups, namely 22:6n-3 and 20:4n-6, respectively. The reciprocal changes in n-9 PUFA and n-3/n-6 PUFA in TF cell total lipid resulted in the percentage of total PUFA not being significantly affected by changes in salinity. The graded decrease in 18:2n-9 with increasing salinity in TF cells was observed in all the major glycerophospholipids but especially PE, PI and PS. Increasing salinity resulted in graded increases in the percentages of 22:6n-3 in PE and PS in TF cells. The quantitatively greatest increase in the percentage of n-6 PUFA in TF cells occurred with 20:4n-6 in PC, PE and PL. There were less significant changes in the fatty acid compositions of glycerophospholipids in AS cells. However, the proportion of total n-3 + n-6 PUFA in PE varied reciprocally with the proportion of dimethylacetals in response to salinity. Similar reciprocal changes between fatty acids in response to salinity were also evident in the quantitatively more minor glycerophospholipids PS and Pl. In PS, the percentage of 22:6n-3 was significantly lower at 400 mOsm kg^–1 whereas the proportion of total monoenes was significantly higher at that salinity. A similar inverse relationship between total monoenes and 20:4n-6 (and, to a lesser extent total saturates) in response to salinity was noted in PI. The results show that environmental salinity, without whole-body physiological stimuli, has direct effects on the fatty acid composition of major glycerophospholipid classes in fish cells and that these effects differ in cells from different fish speciesAbbreviations ANOVA analysis of variance - BHT butylated hydroxytoluene - BSA bovine serum albumin - DMA dimethylacetals - EMEM Eagle's minimal essential medium - FCS fetal calf serum - GC gas chromatography - HBSS Hank's balanced salt solution (without Ca²⁺ and Mg²⁺) - OP osmotic pressure - PC phosphatidylcholine - PE phosphatidylethanolamine - PI phosphatidylinositol - PS phosphatidylserine - PUFA polyunsaturated fatty acid - TLC thin-layer chromatography     

Influence of salinity on the energetics of gill and kidney of Atlantic salmon (Salmo salar)

The effect of seawater acclimation and adaptation to various salinities on the energetics of gill and kidney of Atlantic salmon (Salmo salar) was examined. Smolts and non-smolts previously reared in fresh water were exposed to a rapid increase in salinity to 30 ppt. Plasma osmolarity, [Na⁺], [Cl^–], [K⁺] and [Mg⁺⁺] increased in both groups but were significantly lower in smolts than non-smolts. Gill Na⁺, K⁺-ATPase specific activity, initially higher in smolts, increased in both groups after 18 days in seawater. Kidney Na⁺, K⁺-ATPase specific activity was not affected by salinity in either group. Gill and kidney citrate synthase specific activity was not affected by seawater exposure in smolts but decreased in non-smolts. In a second experiment, Atlantic salmon smolts reared in fresh water were acclimated to 0, 10 or 30 ppt seawater for 3 months at a temperature of 13–14°C. Gill Na⁺, K⁺-ATPase was positively correlated with salinity, displaying 2.5- and 5-fold higher specific activity at 10 and 30 ppt, respectively, than at 0 ppt. Kidney Na⁺, K⁺-ATPase specific activity was not significantly affected by environmental salinity. Citrate synthase and cytochrome c oxidase specific activities in gill were slightly (6–13%) lower at 10 ppt than at 0 and 30 ppt, whereas kidney activities were lowest at 30 ppt. Oxygen consumption of isolated gill filaments was significantly higher when incubated in isosmotic saline and at 30 ppt than at 0 ppt, but was not affected by the prior acclimation salinity. The results indicate that although high salinity induces increased gill Na⁺, K⁺-ATPase activity, it does not induce substantial increases in metabolic capacity of gill or kidney.     

Influence of temperature and salinity on the yellowleg shrimp, Penaeus californieinsis Holmes, prophenoloxidase system

The effects of salinity and temperature on plasma protein concentration and total haemocytic prophenoloxidase (proPO) were determined. Groups of 10 juvenile yellowleg shrimp, Penaeus californiensis Holmes, were acclimated for 20 days at different salinities (28%o, 32%o, 36%o, 40%o and 44%o at 25 °C) or temperatures (18, 22, 25, 28 and 32 °C at 36%o). While total protein levels were not affected, the quantities of proPO increased as salinity was elevated. Temperature affected both haemolymph parameters, showing a significant decrease in proPO at 32 °C, and an increase of protein at 28 and 32 °C. These results may help to explain the elevated disease susceptibility of shrimp at higher salinities and/or temperatures.     

A metabolic approach to understanding adaptation to sea water by endangered Persian sturgeon,Acipenser persicus fingerlings

In this study, metabolic responses of Persian sturgeon fingerlings to hyperosmotic condition were investigated by NMR‐based metabolomics. Persian sturgeon fingerlings (n = 2010, mean total weight: 3.2 ± 0.6 g; mean total length: 8.5 ± 1.5 cm) were held in freshwater (FW) for 96 hr and then acclimated in brackish water (BW) (12 g/L) for 24 hr. Blood samples were taken before and after salinity acclimation. The major metabolite changes corresponding to salinity acclimation were related to amino acids, osmolytes and energy metabolites. The plasma glucose levels increased significantly after 24 hr acclimation in BW (p < .05). Other energetic metabolites (acetate, acetoacetate, beta‐hydroxybutyrate, phosphocreatine, creatine, glycerol) showed no significant changes after 24 hr salinity challenge (p > .05). The osmolytes (taurine, trimethylamine‐N‐oxide, choline, N,N‐dimethylglycine) and amino acids (aspartate, glutamate, glutamine, leucine, phenylalanine, β‐alanine, histidine, threonine, cysteine) declined significantly after 24 hr acclimation in BW (p < .05). However, the levels of glycine elevated after 24 hr acclimation in BW (p < .05). Other amino acids including aspargine, isoluecine, Tyrosine, Tryptophan, Valine, and Lysine showed no significant changes after salinity challenge (p > .05). The considerable decreases in almost all plasma amino acids and all osmolytes showed specific importance of these metabolites in osmotic adaptation of fish in BW. Also, it seems that Persian sturgeon fingerlings rely more on oxidation of glucose to meet energetic requirements of osmoregulation than oxidation of lipids, as we observed no detectable changes in metabolites associated with lipid oxidation during osmotic acclimation in BW. Our results may help to understand osmoregulation in a chondrostei fish species from a metabolic approach.     

Metabolism of fatty acids in fish: III. Combined effect of environmental temperature and diet on formation and deposition of fatty acids in the carp,Cyprinus carpio Linnaeus 1758

Formation and deposition of fatty acids in carp maintained on diets differing in total fat as well as linolenic acid content was investigated by following the incorporation of (1-¹⁴C)-acetate into liver total- and phospholipid fatty acids at two extreme temperatures (5° and 25°C). Excess dietary linolenic acid was deposited in triglycerides but not in phospholipids. The formation and level of phospholipid docosahexenoic acid was, however, dependent on the amount of linolenic acid in the diet. Despite the vast quantities of ingested linolenic acid, the carp on diets containing sufficient essential fatty acid maintained similar membrane fluidities as judged from the ratio of saturated to unsaturated fatty acids. Decrease of the environmental temperature brought about a reduction in the rate of formation of palmitic acid and an increase in the rate of formation of docosahexenoic acid in carp receiving sufficient essential fatty acid. Consequently, the level of palmitic acid decreased and that of docosahexenoic acid increased in the liver phospholipids in carp and a number of other fish species. Essential fatty acid deficient carp were unable to increase the rate of production of long chain polyunsaturated fatty acids upon exposure to cold. The results are discussed from the point of view of adaptation of membrane fluidity to the temperature by fish, and the importance of docosahexenoic acid in this process is emphasized.     

The Effects of Temperature, Age, and Acclimation to Salinity on the Survival of Farfantepenaeus paulensis Postlarvae

Abstract.— Salinity tolerance limits during the ontogenetic development of Farfantepenaeus paulensis postlarvae (PL) were determined at different temperatures. Initially, PL 10, 20, 30, 40, 60 and 80 maintained in 30 ppt (parts per thousand) salinity, 22‐25 C, were directly transferred to 15 combinations of salinity (2, 5, 10, 20 and 30 ppt) and temperature (15, 20 and 30 C) for 96 h. Irrespective of age or salinity, higher survival rates were registered at 25 C. PL 10 suffered high mortality, especially at low salinities combined with low (15 C) or high (30 C) temperatures. From PL 20 to PL 40, an increase in survival was observed in all combinations. For PL 60 and 80, tolerance to low salinity was reduced, suggesting that PL have a maximum age by which they are able to develop adaptability to low salinities. In general, the effect of temperature contributed more significantly to mortality in PL 10 and PL 30, but its influence decreased afterwards. From PL 40, salinity becomes the main factor determining mortality. In order to examine the effects of acclimation to salinity on the tolerance limits, a second set of experiments was performed with PL 5, 10, 15 and 25 acclimated to 2, 5, 10, 20 and 30 ppt, 25 C, over a 5‐d period. Postlarvae were then transferred to different salinity levels (2, 5, 10, 20 and 30 ppt) and kept for 96 h. High mortality of PL 10 occurred after direct transfer from high to intermediate/low salinity levels. Although the acclimation to salinity increased survival, it was still poor. An increase in the salinity tolerance was observed from PL 15 to 30, even with no acclimation. Results indicate that PL 10 do not have a fully developed osmoregulatory capacity to cope with low and/or abrupt changes of salinity. It is recommended that non‐acclimated PL 10 should only be released in environments with salinity at or above 20 ppt. If acclimation is carried out, PL may be released in salinities above 10 ppt. The release of PL 10 in salinities below 5 ppt may result in mortality rates of up to 70%. The best age for the release of non‐acclimated F. paulensis PL in environments with low and/ or wide fluctuations of salinity would he PL 15‐30.     

The fatty acid composition of Nereis diversicolor cultured in an integrated recirculated system: Possible implications for aquaculture

The potential of solid waste originating from a recirculated fish culture system, i.e. faecal material, uneaten food pellets and bacterial biofilms was examined as food source for the marine polychaete Nereis diversicolor. These polychaetes could be a valuable food for fish if they provide essential fatty acids to the fish. Therefore, we analysed the fatty acid profiles from feed and faecal materials, the sediment as well as the cultured organisms — fish and several batches of N. diversicolor — from an integrated recirculating aquaculture system.The major fatty acids (saturated, monounsaturated and polyunsaturated) for all analysed fish feed, fish and faeces samples were C16:0, C18:1 and C22:6 (n − 3), accounting for 48% to 57% of the fatty acids in the samples. The major fatty acids within the sediment were C16:0, C18:1 and C18:3 (n − 3), accounting for 61% of the total fatty acids. The samples of N. diversicolor revealed C16:0, C18:1 and C20:5 (n − 3) as the major fatty acids. Combined, they accounted for 56% of the total fatty acids detected within the worm samples.The results indicate that a recycling or even an upgrade of excreted feed nutrients such as fatty acids, which were otherwise discharged, can be achieved through integrated aquaculture combining fish and worm culture.     

Aurantiochytrium sp. meal as DHA source in Nile tilapia diet,part II: Body fatty acid retention and muscle fatty acid profile

Nile tilapia juveniles (8.35 ± 0.80 g) were fed on four levels (0.0%; 0.5%; 1.0%; 2.0%, 4.0%) of Aurantiochytrium sp. meal (ALL‐G‐RICH?), a source of docosahexaenoic acid (DHA). The 1% Aurantiochytrium sp. meal diet was compared to a control diet, which contained the same amount of DHA as cod liver oil (CLO) at 1.7% diet. Groups of 25 fish were stocked in 100 L tanks and fed twice daily until apparent satiation, for 57 days, at 28°C. Increasing dietary Aurantiochytrium sp. meal reduced the body retention of DHA and n‐3 polyunsaturated fatty acids (n‐3 PUFA) but increased the body retention of alpha‐linolenic (α‐LNA), linoleic (LOA) and n‐6 polyunsaturated fatty acids (n‐6 PUFA). Fatty acid profile in tilapia muscle was affected by increasing dietary inclusions of Aurantiochytrium sp. meal, with an increase in DHA, α‐LNA, n‐3 PUFA and n‐3 long chain‐polyunsaturated fatty acids (n‐3 LC‐PUFA) but a decrease in monounsaturated fatty acids (MUFA), n‐6 PUFA and n‐6 long‐chain polyunsaturated fatty acids (n‐6 LC‐PUFA). There was a larger body retention of DHA, α‐LNA, LOA, n‐3 PUFA and n‐6 PUFA fatty acids and a higher percentage of DHA, n‐3 PUFA and n‐3 LC‐PUFA in muscle fatty acid profile in fish fed on CLO diets than in those fed on 1% Aurantiochytrium sp. Therefore, Aurantiochytrium sp. meal is an alternative source of DHA for Nile tilapia diets.