The distribution of fatty acids in gill phospholipids of the Chinese crab Eriocheir sinensis

The fatty acid composition of the different classes of phospholipids isolated from 10,000 g fractions of posterior and anterior gills of fresh water-acclimatized Chinese crabs (Enocheir sinensis) has been analysed by two-dimensional TLC and GLC. All the phospholipids, especially PE and DPG, contain large amounts of long chain, polyunsaturated fatty acids. In PC and PE of both the anterior and posterior gills, polyenic fatty acids (particularly the ω-3-acid family) were found to be mainly incorporated in the 2-positon of the glycerol molecule. The ω-3-fatty acids/ω-6-fatty acids ratio in each class of phospholipids is higher in the posterior gills than in the anterior ones. The sum of polyunsaturated fatty acids and the unsaturation index of DPG are more important in the posterior gills than in the anterior ones. It is suggested that negatively charged unsaturated DPG and that the contrast of activities of ω-6- and ω-3-acids found in phospholipids provide a suitable lipid environment for optimal activity of the transport mechanisms at work in posterior gills of the Chinese crab.     

The biosynthesis of beta-carboline and quinolizidine alkaloids of Alangium lamarckii

The incorporation of tryptamine, dopamine, N-deacetylisoipecoside, N-deacetylipecoside into alangimarckine, deoxytubulosine and ankorine and of strictosidine and vincoside into alangimarckine and deoxytubulosine in young Alangium lamarckii Thw. (Alangiaceae) has been studied and specific utilisation of N-deacetylisoipecoside demonstrated. Parallel experiments with nordeoxytubulosine and deoxytubulosine suggested that O-methylation precedes condensation of protoemetine with tryptamine and further the reduction of ethylene side chain takes place before condensation. Hydroxylation at C-8 in the trans-quinolizidine moiety is the terminal step in the biosynthesis of alangimarckine.     

Hepatic mitochondrial membrane lipid environment and protein nutrition

Effect of feeding rice diet with and without lysine and threonine supplementation on hepatic mitochondria and its inner and outer membrane proteins, enzymes and phospholipids has been studied. The exchange of phosphatidylcholine and phosphatidylethanolamine between microsomes and mitochondria has also been studied under these conditions. Deficient diet lead to significant decrease in proteins as well as activities of monoamine oxidase, succinate dehydrogenase, cytochrome a + a3 and cytochrome c in mitochondria and its inner and outer membranes. Feeding of the deficient diet also significantly reduced total phospholipids and PC in mitochondria and its outer mitochondrial membrane. In the inner mitochondrial membrane, only PE and cardiolipin were reduced. The incorporation (DPM/microgram PLP) of [methyl-3H]choline and [methyl-14C]methionine into PC of mitochondria and its outer membrane and that of 32Pi into PC and PE of outer mitochondrial membrane but only into PC of inner mitochondrial membrane were significantly reduced in the deficient group. The exchange rates of PC and PE between microsomes and mitochondria were reduced in the deficient group. Supplementation of the deficient diet with lysine and threonine profoundly improved the above biochemical lesions as compared to casein fed rats.     

Phospholipids composition and metabolism in the hemolymph of Carcinus maenas (Crustacea,Decapoda)—Effect of temperature

• 1.1. The distribution of different phospholipids and the repartition of fatty acids extracted from hemolymph of crab Carcinus maenas are analysed.
• 2.2. The action of the temperature on the lipid composition is also determined: an increase of content of PE and a slight rise of the degree of unsaturation of fatty acids are found at lower temperatures.
• 3.3. The specific radioactivity of total phospholipids, phosphatidyl-choline and phosphatidylethanolamine from hemolymph of Carcinus maenas is studied from two radioactive precursors (³²Phosphorus and ³H]ethanolamine). Results suggested that the conversion of PE into PC by methylation could take place in hepatopancreas of Carcinus maenas.
• 4.4. The specific radioactivity of phospholipids from these two same radioactive compounds is increased following a variation in the environmental temperature.
• 5.5. The composition of hemolymph lipids could be a direct reflection of the lipid metabolism of the hepatopancreas and that the temperature alters the rate of the phospholipid exchange between hepatopancreas and hemolymph.
• 6.6. It is suggested that these lipid alterations occur in order to permit crab Carcinus maenas to support large changes in environmental temperatures.

     

The thermotropic behavior and fatty radical composition of major phospholipids of the tanner crab <Emphasis Type="Italic">Chionoecetes bairdi</Emphasis> Rathbun, 1924

This study examines the fatty radical (FR) composition and heat-induced crystalline to liquidcrystalline phase transitions of phosphatidylcholine (PC) and phosphatidylethanolamine (PE) from the gills, hepatopancreas, gonads, and muscle of the tanner crab Chionoecetes bairdi, which was collected in the summer at a near-bottom water temperature of 2.8°C. The location of the PC and PE thermograms below 2.8°C indicates the functionally optimal liquid crystalline state of the membrane lipid matrix. The proximity of the thermogram profiles of PC and PE from the different organs and tissues of C. bairdi and significant overlapping of the temperature areas of transitions (symbatic behavior) correlate with a similar composition of major FR and their total parameters in PC and PE. The obtained data point to the effective adaptation of the bairdi crab to low water temperatures and to the need for adaptive changes in the FR composition or change of habitat with increasing temperature. The thermotropic behavior of muscle PC, in which the greater part of the thermogram is in the temperature range from 2.8 to 32°C, suggests a potential for the tanner crab to adapt to increased temperatures.     

Phospholipid composition and metabolism of crustacean gills as related to changes in environmental salinities: relationship between Na+-K+-ATPase activity and phospholipids

The phospholipid composition and metabolism are studied in crustacean gills. It is reported that branchiae are rich in PC, PE and DPG and abundant in long chain polyunsaturated fatty acids (20:4 omega 6 and 20:5 omega 3 acids). The pathways of phospholipids synthesis appear similar to those described for vertebrates. It is demonstrated that there exist significant differences in the level of phosphatides between the anterior and posterior gills of Eriocheir sinensis. No matter what the salinity, the three more posterior located gills of Chinese crabs are shown to contain much more unsaturated phospholipids (PE and DPG). This is particularly true when animals are acclimated to dilute media. Moreover, lipids of posterior gills appear more fluid than the anterior ones as reported by the values of the degree of fluorescence polarization and the index of unsaturation of fatty acids. It is suggested that these lipid changes may indicate the existence of a functional difference between the various branchiae of euryhaline Eriocheir sinensis with respect to their ability to transport salt. It is shown that the renewal of DPG and PS is increased in posterior gills isolated from freshwater Chinese crabs. It is postulated that the enhanced formation of DPG in posterior gills is an indicator of an increased synthesis of mitochondria having as principal function to produce the necessary energy for the Na+ uptake. An attempt is made to correlate the PS metabolism and the Na+-K+-ATPase activity which is particularly located in the mitochondrial fractions of the three pairs of posterior gills.     

Incorporation of ω6 polyunsaturated fatty acids into phospholipids of the crab Carcinus maenas

The incorporation in vivo of ¹⁴C-18:2 ω6 and ³H-20:4 ω6 fatty acids in phospholipids isolated from gills, hepatopancreas and hemolymph of the crab Carcinus maenas was analysed. PC was the most heavily labelled phospholipid from these ω6-unsaturated fatty acids and appeared to play an important part in the phospholipids metabolism in Crustaceans. The pathway of fatty acids synthesis in phospholipids of C. maenas seems to be similar to those described for mammals. It is at the level of tissue Pl of C. maenas that the renewal of the 20:4 ω6 fatty acid is the most important. It is suggested that the rapid reorganization of phospholipid molecular species composition in the crab is checked by deacylation—reacylation cycle.     

Continuous equilibration of phosphatidylcholine and its precursors between endoplasmic reticulum and mitochondria in yeast

In Saccharomyces cerevisiae phosphatidylcholine (PC) is synthesized in the ER and transported to mitochondria via an unknown mechanism. The transport of PC synthesized by the triple methylation of phosphatidylethanolamine was investigated by pulsing yeast spheroplasts with l-[methyl-3H]methionine, followed by a chase with unlabeled methionine and subcellular fractionation. During the pulse, increasing amounts of PC and its mono- and dimethylated precursors (PMME and PDME, respectively) appear in similar proportions in both microsomes and mitochondria, with the extent of incorporation in microsomes being twice that in mitochondria. During the chase, the [3H]-methyl label from the precursors accumulates into PC with similar kinetics in both organelles. The results demonstrate that transport of methylated phospholipids from ER to mitochondria is 1) coupled to synthesis, 2) not selective for PC, 3) at least as fast as the fastest step in the methylation of PE, and 4) bidirectional for PMME and PDME. The interorganellar equilibration of methylated phospholipids was reconstituted in vitro and did not depend on ongoing methylation, cytosolic factors, ATP, and energization of the mitochondria, although energization could accelerate the reaction. The exchange of methylated phospholipids was reduced after pretreating both microsomes and mitochondria with trypsin, indicating the involvement of membrane proteins from both organelles.     

Comparative metabolism of phospholipids of osmoregulation effector organs in European eel (Anguilla anguilla)]

The phospholipid composition from various organs of the fresh water eel, such as gill, kidney, gut, liver and muscle, were determined by thin-layer chromatography. The major phosphatides found in these tissues were PC, PE and SPH and minor constituents PS, PI, DPG, AP and also LPC in the gut. A greater percentage of PS and SPH occurs in the osmoregulatory effector organs such as gill, kidney, and gut. From in vivo comparative kinetic studies of the 32P incorporation into the phospholipids, between 6 and 48 hours, certain remarkable features of phospholipid metabolism have been found in these tissues. A low uptake of inorganic 32P into the tissue lipid phosphorus was observed in the eel at 15 degrees C. The specific activity of the lipid phosphorus increased continuously in all tissues during 48 hours after 32P injection. During this experimental period, phosphatidic acid and phosphatidyl inositol fractions were labelled most rapidly in gill, kidney and gut, while the specific activity of the phosphatidyl choline fraction remained low in these organs. In liver, the rate of PC formation appears to be faster than the PI and PE biosynthesis. In gill and gut, the PE showed greater turnover than the PC as measured by 32P incorporation. In the eel, an euryhalin fish, the DPG of osmoregulatory effector organs has a high specific activity at all times. PS showed only a high specific activity in the gill. Labelling of SPH occured slowly in the various tissues only becoming evident after 24 hours. The results are compared with those published for other poikilotherm and homeotherm vertebrates. Relative differences between the turnover of various tissue phosphatides are discussed with of reference to the general scheme on phospholipid biosynthesis and to the physiological functions of the various organs.     

A morphological study on gills of a crab acclimated to fresh water

The gills of the fully euryhaline Chinese crab Eriocheir sinensis were studied by light and electron microscopy. In these Phyllobranchiates, the gills consist of a double row of lamellae extending laterally from a central shaft. Haemolymph flow pattern inside the gill is described and the existence of a complex secondary vascularization inside the platelets is reported. It is shown that important differences exist between the ultrastructure of the three anterior and the three posterior pairs of large gills. The epithelium of the posterior gills is much thicker and possesses an extensive elaboration of the plasma membranes in the form of infoldings, crypts and interdigitations, along which are packed numerous mitochondria. The presence of such a complex membrane system opening to the extracellular space and closely associated with mitochondria is common to all salt-transporting tissues. This study corroborates the idea that the posterior pairs of gills of Eriocheir sinensis are the only ones implicated in active Na+ uptake when the crab lives in dilute aquatic environment. The epithelium of anterior gills is much thinner and the cells poor in intracellular organelles. It seems to be involved essentially in respiration. Thus this work clearly corroborates the existence already suggested by physiological approach of a functional difference between the different pairs of E. sinensis branchiae with respect to their participation in the respiration and in the regulation of the blood ions content. Common to both types of gills is the presence of a lamellar septum separating the haemolymph space into two compartments. The part played by that structure in determining the pattern of haemolymph flow, together with periodic bridges forming pillars across the haemolymph space, is emphasized.     

Les phospholipides: relation entre leur nature et i''evolution des systèmes endomembranaires chez les champignons filamenteux

Phospholipids of two filamentous fungi, Mucor mucedo and Aspergillus ochraceus, cultivated under identical conditions, were separated by column chromatography, thin layer chromatography and identified by autoradiography. They contain mainly phosphatidylcholine (PC), phosphatidy ethanolamine (PE) and phosphatidylserine (PS). PE. is the most abundant molecule of the phospholipids in these two moulds, but the ratio PE/PC = 3,4 for M.mucedo while it is only 1.3 for A.ochraceus. Linoleic acid is more important in the latter fungus. Correlations between the phosphatidylcholine content, its evolution, the structural stage of a microorganism and the complexity of the membranary systems are suggested.     

Alterations in wheat pollen lipidome during high day and night temperature stress

Understanding the adaptive changes in wheat pollen lipidome under high temperature (HT) stress is critical to improving seed set and developing HT tolerant wheat varieties. We measured 89 pollen lipid species under optimum and high day and/or night temperatures using electrospray ionization‐tandem mass spectrometry in wheat plants. The pollen lipidome had a distinct composition compared with that of leaves. Unlike in leaves, 34:3 and 36:6 species dominated the composition of extraplastidic phospholipids in pollen under optimum and HT conditions. The most HT‐responsive lipids were extraplastidic phospholipids, phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol, phosphatidic acid, and phosphatidylserine. The unsaturation levels of the extraplastidic phospholipids decreased through the decreases in the levels of 18:3 and increases in the levels of 16:0, 18:0, 18:1, and 18:2 acyl chains. PC and PE were negatively correlated. Higher PC:PE at HT indicated possible PE‐to‐PC conversion, lower PE formation, or increased PE degradation, relative to PC. Correlation analysis revealed lipids experiencing coordinated metabolism under HT and confirmed the HT responsiveness of extraplastidic phospholipids. Comparison of the present results on wheat pollen with results of our previous research on wheat leaves suggests that similar lipid changes contribute to HT adaptation in both leaves and pollen, though the lipidomes have inherently distinct compositions.     

Phospholipid topology and flip-flop in intestinal brush-border membrane

The topological distribution of the two major phospholipids of brush-border membrane, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), has been investigated using brush-border membrane vesicles from rabbit small intestine. Bee venom phospholipase A2 and phosphatidylcholine exchange protein from bovine liver were used as membrane probes. It is shown that the brush-border membrane retains its integrity under conditions of phospholipase hydrolysis and intermembrane phospholipid exchange. Kinetic analysis of the data of phospholipase hydrolysis and phospholipid exchange at temperatures under 10 degrees C shows that both PC and PE occur in two pools: a minor (about 25%) more readily accessible pool and a major one (about 75%) less readily available. The rate of PC exchange between these two pools is relatively fast. The half-time derived under conditions of phospholipase hydrolysis is of the order of 20 min. Under conditions of phospholipid exchange the exchange rates may be even faster. The difference in exchange kinetics observed with the two methods of probing is probably due to changes in membrane properties such as the bilayer fluidity induced by the probing process itself. It is proposed that the two pools represent the transverse distribution of the phospholipids. The two major phospholipids of brush-border membranes, PC and PE, would be distributed mainly on the inner (cytoplasmic) side of the brush-border membrane. The phospholipid exchange between the brush-border vesicles and unilamellar phosphatidylcholine vesicles in the presence of phosphatidylcholine exchange protein reveals that significant quantities of phospholipid are taken up by brush-border membrane independently, i.e., in a separate process independent of the exchange protein-catalyzed phosphatidylcholine exchange.     

Effects of ethanol on the incorporation of free fatty acids into cerebral membrane phospholipids

Chronic ethanol exposure is known to affect deacylation-reacylation of membrane phospholipids (PL). In our earlier studies we have demonstrated that chronic exposure to ethanol (EtOH) leads to a progressive increase in membrane phospholipase A2 (PLA2) activity. In the current study, we investigated the effects of chronic EtOH exposure on the incorporation of different free fatty acids (FFAs) into membrane PL. The results suggest that the incorporation of fatty acids into four major PL varied from 9.6 fmol/min/mg protein for docosahexaenoic acid (DHA) into phosphatidylinositol (PI) to 795.8 fmol/min/mg protein for linoleic acid (LA) into phosphatidylcholine (PC). These results also suggest a preferential incorporation of DHA into PC; arachidonic acid (AA) into PI; oleic acid into phosphatidylethanolamine (PE) and PC; LA into PC and stearic acid into PE. Chronic EtOH exposure affected the incorporation of unsaturated fatty acid into PI, phosphatidylserine (PS) and PC. However, EtOH did not affect significantly the incorporation of any of the fatty acids (FA) studied into PE. No significant differences were observed with the stearic acid. It is suggested that acyltransferases may play an important role in the membrane adaptation to the injurious effects of EtOH.     

Seasonal changes in thermotropic behavior of phosphatidylcholine and phosphatidylethanolamine in different organs of the ascidian Halocynthia aurantium

Differential scanning calorimetry and polarising microscopy were used to investigate the crystal-liquid crystal-isotropic melt phase transitions of phosphatidylcholine (PC), and phosphatidylethanolamine (PE), isolated from muscles, gill pouches, gonads and digestive glands of Halocynthia aurantium, collected in summer and winter. We also analyzed the fatty chain composition of these phospholipids. In summer, the crystalline to liquid crystalline phase transitions of PC and PE from different organs were more co-operative than in winter. Their peak maximum temperatures were close and temperature ranges overlapped for summer samples. Peak maximum temperatures of winter samples decreased sharply, by 18-27 degrees C for PC and by 10-44 degrees C for PE, respectively, depending on the organ. Total heat changes of transitions also decreased. Thermograms were completely located at temperatures below -1.7 degrees C (minimal temperature of seawater in winter). In contrast to summer samples, peak maximum temperatures for PC and PE in winter differed significantly, (by 14-30 degrees C depending on organ), while the temperature ranges of their transitions still showed considerable overlap. Simultaneously, the temperature ranges of the liquid crystalline to isotropic phase transitions decreased. The main reason for changes in thermotropic behavior of phospholipids seems to be the decrease of saturated/unsaturated ratios. The existence of stable and thermoadaptative labile phospholipid pools in the membrane structure is proposed. The relationship of these transitions to low- and high-temperature adaptation is discussed.     

Solid- and liquid-phase equilibria in phosphatidylcholine/phosphatidylethanolamine mixtures. A calorimetric study

Phase diagrams have been determined for mixing of binary mixtures of phosphatidylethanolamines (PE) with phosphatidylcholines (PC), using high-sensitivity differential scanning calorimetry and allowing extensive incubation times to equilibrate samples in the solid phase. All of the PE-PC systems examined, which contained saturated or trans-unsaturated PC components, showed limited solid-phase miscibility, chiefly because the PC component can adopt more solid phases than the PE component. For the dielaidoyl PE-PC system, the lamellar-to-hexagonal II transition endotherm seen at 63.5 degrees C for the pure PE is shifted to considerably higher temperatures upon incorporation of even low mole fractions of PC. All of the PE-PC systems examined here reveal a complete miscibility in the liquid phase, including the dipalmitoyl PE-dielaidoyl PC system for which limited liquid-phase miscibility had previously been suggested (Wu, S-H. and McConnell, H.M. (1975) Biochemistry 14, 847-854). However, PE-PC mixing appears to be less nearly ideal than the mixing of either PE or PC with anionic phospholipids. Our results demonstrate that calorimetry can be useful in determining accurate phase diagrams for lipid mixtures of this type, but only if proper attention is given to the existence and the proper equilibration of multiple solid phases in these systems.     

Studies on the preferential incorporation of [3H]glycerol over [32P]phosphate into major phospholipids of human platelets

It is well known that platelets readily incorporate radioactive glycerol, but not radioactive phosphate into phosphatidylcholine (PC) and phosphatidylethanolamine (PE) in vitro, thus not in accordance with de novo synthesis according to the Kennedy pathway. In attempts to understand the reason for the discrepancy, gel-filtered platelets were incubated simultaneously with [32P]Pi and [3H]glycerol, and the specific and relative radioactivities of products and intermediates were determined. Both precursors were incorporated into phosphatidylinositol (PI) with a 32P/3H ratio similar to that in glycerol 3-phosphate (in accordance with the Kennedy pathway). However, PC and PE obtained a much lower ratio. The specific 32P radioactivity in phosphorylcholine was similar to that of the gamma-phosphoryl of ATP and 650-times higher than that of PC. The specific 32P radioactivity of phosphorylethanolamine was 20-times less than that of phosphorylcholine. Both mass and 32P labelling of CDP-choline were below the detection limits. It is concluded that the incorporation of [32P]Pi into PC via phosphorylcholine is insignificant while the preferential incorporation of [3H]glycerol could be explained by exchange of diacyl[3H]glycerol in the reversible choline phosphotransferase (CDP-choline: 1,2-diacylglycerol cholinephosphotransferase) reaction. The same mechanism would explain the preferential incorporation of 3H over 32P into PE, although dilution of 32P at the phosphorylethanolamine stage would account for part of the feeble 32P incorporation. Although other mechanisms are also possible, our results clearly show that the appearance of [3H]glycerol in PC and PE is not a reliable method of monitoring de novo synthesis of these phospholipids.     

The incorporation of unsaturated fatty acids of the n-9, n-6, and n-3 families into individual phospholipids by isolated hepatocytes of thermally-acclimated rainbow trout, Salmo gairdneri

Rates of incorporation of 1-14C-oleic (18:1n9), -linoleic (18:2n6), and -linolenic (18:3n3) acids into individual phosphatides were determined in isolated hepatocytes from cold (5 degrees C)- and warm (20 degrees C)-acclimated rainbow trout, Salmo gairdneri. Fatty acid incorporation into phosphatidylcholine (PC) exceeded that into all other phospholipids, but at assay and acclimation temperatures of 5 degrees C, incorporation into phosphatidylethanolamine (PE) was generally intermediate between that of PC and the remaining phosphatides. Specific radioactivities (ratios of percentage isotope incorporation-to-mole percentage of phosphatide) were consistently less than one for both PC and PE, and greater than one for phosphatidic acid (PA), lysophosphatidylcholine (LPC), phosphatidylserine (PS), and cardiolipin (CL). For PS, specific radioactivities were greater in cold- than warm-acclimated trout, and greater at 5 degrees C than 20 degrees C. Rates of oleate incorporation were generally higher, and rates of incorporation of 18:2 and 18:3 lower in cold- than warm-acclimated trout. Most phospholipids demonstrated a clear preference for the incorporation of 18:2 when assayed at 20 degrees C; however, at 5 degrees C the incorporation of 18:2 was reduced and 18:3 was generally the preferred substrate. A reduction in assay temperature from 20 degrees C to 5 degrees C also shifted the incorporation of 18:2 away from PC into PS and PA. These data were interpreted to indicate 1) a cold-induced activation of PS metabolism, possibly resulting in elevated levels of PE; 2) lower rates of general acyl group turnover in animals acclimated to 5 degrees C than 20 degrees C; 3) a specificity to the acclimation response that favors the incorporation at cold temperatures of polyunsaturated fatty acids, but not the parent acids from which they are derived; and 4) the participation of a deacylation-reacylation cycle in the metabolism of phospholipids, particularly at cold temperatures.     

Solid- and liquid-phase equilibria in phosphatidylcholine / phosphatidylethanolamine mixtures. A calorimetric study

Phase diagrams have been determined for mixing of binary mixtures of phosphatidylethanolamines (PE) with phosphatidylcholines (PC), using high-sensitivity differential scanning calorimetry and allowing extensive incubation times to equilibrate samples in the solid phase. All of the PE-PC systems examined, which contained saturated or trans-unsaturated PC components, showed limited solid-phase miscibility, chiefly because the PC component can adopt more solid phases than the PE component. For the dielaidoyl PE-PC system, the lamellar-to-hexagonal II transition endotherm seen at 63.5°C for the pure PE is shifted to considerably higher temperatures upon incorporation of even low mode fractions of PC. All of the PE-PC systems examined here reveal a complete miscibility in the liquid phase, including the dipalmitoyl PE-dielaidoyl PC system for which limited liquid-phase miscibility had previously been suggested (Wu, S-H. and McConnell, H.M. (1975) Biochemistry 14, 847–854). However, PE-PC mixing appears to be less nearly ideal than the mixing of either PE or PC with anionic phospholipids. Our results demonstrate that calorimetry can be useful in determining accurate phase diagrams for lipid mixtures of this type, but only if proper attention is given to the existence and the proper equilibration of multiple solid phases in these systems.     

Thermoadaptation and fatty acid composition of main phospholipids of the small-scaled redfin <Emphasis Type="Italic">Tribolodon brandti</Emphasis> under natural and experimental conditions

The fatty acid (FA) composition of the main membrane phospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), was investigated in the muscle, gills, and liver of the small-scaled redfin Tribolodon brandti (Dybowskii, 1872) at different temperatures under natural and experimental conditions. It was established that a water temperature decrease in the natural habitat was accompanied by an increase in polyunsaturated fatty acid contents and the unsaturation index, mainly at the expense of FAs of the ω3 series (20:5ω3 and 22:6ω3), and by a decrease in saturated fatty acid levels in PC and PE. A similar, but less pronounced tendency was revealed in experiments with a rapid lowering of water temperature. These findings suggest the weak adaptation ability of the small-scaled redfin to a drastic shift of environmental temperature. Temperature changes produced the greatest alterations in the FA composition of phospholipids in the liver and the smallest changes occurred in muscle tissue.