Ana Bolaños

Lipid and fatty acid composition of ovaries from wild fish and ovaries and eggs from captive fish of white sea bream (Diplodus sargus)

Abstract The fatty acid composition of ovaries from wild white sea bream and ovaries and eggs of captive white sea bream were investigated to estimate the fatty acid requirements of this species. The total lipid (TL) content in wild fish ovaries was similar to that found in ovaries and eggs from captive fish. The general pattern of the fatty acid distribution in lipid of ovaries from wild fish and ovaries and eggs from captive fish was similar. In total lipid, no significative differences in total monoenes, n −6, n −3 and n −3 highly unsaturated fatty acids (HUFA) were found. However, the relative percentage of specific fatty acids differed between wild and captive fish. Thus, arachidonic acid (20:4 n −6, AA) percentage was higher in wild ovaries than in ovaries and eggs from captive fish, whereas eicosapentaenoic acid (20:5 n −3, EPA) showed the opposite trend. In consequence, wild fish presented a lower EPA/AA ratio in their ovaries when compared with ovaries and eggs of captive fish. These differences were extended to all lipid classes studied (triacylglycerol (TG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE)). The present study suggests that essential fatty acids, specially EPA and AA of the diet supplied to the captive white sea bream broodstocks, do not seem to be in an appropriate proportion for this species.

Effect of dietary supplementation with shrimp on skin pigmentation and lipid composition of red porgy (Pagrus pagrus) alevins

A feeding experiment was conducted on red porgy alevins to investigate the influence of dietary supplementation with shrimp on pigmentation and lipid composition of carcass (muscle and skin) and eyes. To this purpose, red porgy alevins with an initial mean weight of 2.8±1.3 g were divided into six groups. Three groups were fed gilthead seabream commercial pellet (P, 100% pellet), whereas the other three were fed with the commercial pellet and shrimp Pleisonika sp. (PS, 88% pellet:12% shrimp) to provide the diet with a source of carotenoids. After 4 months of feeding, the results showed that PS-fish groups displayed a pink-coloured skin similar to that of the wild fish, whereas P-fish groups showed a dark-grey-coloured skin. Furthermore, a higher total content of carotenoids was found in carcass and eyes from PS-fish groups with respect to P-fish groups. No significant differences in growth, survival or other gross external signs were found between treatments. Total lipid (TL), triacylglycerol (TG), phosphatidylcholine (PC) and phosphatidylethanolamine (PE) of red porgy carcass exhibited a specific fatty acid profile. However, the general patterns of the fatty acid distribution in lipids of carcass and eyes from both groups of fish (P and PS) were similar, and only slight differences were found mainly in carcass for some of the fatty acids. We conclude that the natural carotenoids supplied by the shrimp were effectively assimilated by the red porgy and allowed the cultured fish to acquire a skin coloration similar to that of wild fish.

Improvement of the nutritional value of rotifers by varying the type and concentration of oil and the enrichment period

Abstract Several enrichment conditions (type and concentration of oil in culture medium and time of enrichment) were tested in order to study their influence on rotifer ( Brachionus plicatilis ) lipid and fatty acid composition as well as on its population profile. Rotifers pre-fed on bakers yeast ( Saccharomyces cerevisiae ) were enriched with lipid emulsions containing triacylglycerols (TAG) or methyl ester (ME) mixtures at three different concentrations. Rotifers were sampled after 0 (yeast-fed rotifer), 3, 6, 12 and 24h enrichment. At every concentration and time assayed, the highest lipid levels were obtained when using TAG. In spite of the differences existing in saturated and monounsaturated fatty acid composition between the enrichment emulsions, rotifers tended to maintain the level of these fatty acids independently of the enrichment period and oil concentration. Increasing the enrichment period rather than the amount of oil present in the medium was found to be more efficient in increasing the n − 3 highly unsaturated fatty acids ( n − 3 HUFA) level in rotifers. Rotifers reflected a better incorporation of eicosapentaenoic acid (EPA, 20:5 n − 3) than of docosahexaenoic acid (DHA, 22:6 n − 3), regardless of the ratio between both fatty acids in the emulsions. The use of ME as an enrichment source produced greater mortality in egg-carrying females than when using TAG.

Characterization of intestinal Na+–K+-ATPase in the gilthead seabream (Sparus aurata L.). Evidence for a tissue-specific heterogeneity

Abstract Gilthead seabream intestine contains both a Mg 2+ -dependent Na + –K + -ATPase which is completely inhibited by 1×10 −3 M ouabain, and also a residue-ATPase activity that is entirely ouabain-insensitive. The maximal activity of intestinal Na + –K + -ATPase (35.15 μ mol inorganic phosphate (P i ) mg protein −1 h −1 ) was observed in the microsomal fraction at 35°C, pH 7.5, 2–5 mM MgCl 2 , 5 mM ATP, 10 mM K + and 200 mM Na + . The intestinal Na + –K + -ATPase of gilthead seabream exhibits similar characteristics to other teleost Na + –K + -ATPases regarding pH dependence, Mg 2+ /ATP optimal ratios and ouabain sensitivity, but exhibits unusual sensitivity to ionic strength and cation promoted cooperative activation and higher affinity for magnesium and ATP when compared to other marine and euryhaline teleosts. The Arrhenius plot for intestinal Na + –K + -ATPase showed a break point at 15.41°C, with similar activation energies above and below the discontinuity point. The analysis of polar lipid fatty acid composition was correlated to the break point in the Arrhenius plot, suggesting a regulatory role of the lipid microenvironment on the enzyme activity. Finally, the kinetic characteristics, temperature-activity relationship, fatty acid composition and substrate dependence of intestinal Na + –K + -ATPase are compared with literature data and discussed on the basis of the differences between species and also between osmoregulatory tissues. It is concluded that the Na + –K + -ATPase of Sparus aurata is differently and specifically expressed between the osmoregulatory organs.

Intestinal phenylalanine transport in the cultured gilthead bream (Sparus au rata)

Abstract 1. 1. The influx of L-phenylalanine and its effects on the electrophysiology in upper and lower intestine of the cultured fish, Sparus aurata, were measured. 2. 2. The Km and Vmax of l -phenylalanine influx into the tissues were higher in the upper intestine than in the lower intestine. 3. 3. A prominent diffusion-like transport component was also measured in both segments during influx experiments. 4. 4. Addition of l -phenylalanine to the mucosal side of the intestine caused a significant but slow increase in electrical potential difference (PD) and in the short-circuit current (Isc). The increases were dependent on the presence of the sodium ion in the incubation medium. 5. 5. Isc was the hyperbolic function of amino acid concentration characterized by the parameters Vmax (maximum change in Isc) and Km (concentration needed to attain an Isc equal to half the Vmax). 6. 6. Isc-determined Km constants showed slight differences from values obtained from direct measurements of l -phenylalanine uptake into tissue.

Electrical properties of a Na+-dependent phenylalanine transport in Lizard (Lacerta galloti) duodenum

The unidirectional transepithelial fluxes of L-phenylalanine across lizard duodenum were determined in flux chambers. Phenylalanine was preferentially transferred from the mucosal to the serosal fluid. This transport was accompanied by an accumulation of substrate from the mucosal medium into the tissue to a similar level and against a concentration gradient. There was no net movement of phenylalanine when the sodium was substituted by choline. The influx of L-phenylalanine into the epithelial cells of lizard duodenum was examined by incubating slices of intestine in radioactively-labelled solutions of the substrate for 2 min. The steady-state uptake was assessed after similar incubations lasting 45 min. Phenylalanine influx obeys the Michaelis-Menten equation with a Km of 5.1 and is dependent on the presence of sodium ions in the incubation medium. Phenylalanine has been used to induce changes in short-circuit current (delta Isc) across intestine. delta Isc was a hyperbolic function of amino acid concentration characterized by the parameters Jm (maximum change in delta Isc) and Km (concentration needed to attain an delta Isc equal to half the Jm). delta Isc determined Km constants showed good agreement with values obtained from direct measurements of phenylalanine uptake into tissue.

Transport of galactose and sodium across lizard duodenum

Electrical parameters and transepithelial Na+ and galactose transport were determined in vitro across isolated duodenum of Lacerta galloti lizard. Electrical potential difference (PD) and short-circuit current (Isc) were dependent on the presence of Na+ in the bathing solutions. PD and Isc were affected by addition of galactose to the mucosal solution. Isotopic flux of Na+ measurements across short-circuited duodenum showed a net active Na+ absorption. The net flux of Na+ (JNa+net) accounted for the observed Isc. Both (JNa+net) and Isc were increased by the addition of galactose 5 mM to the mucosal solution. Isotopic flux galactose measurements in open-circuit conditions showed a net active galactose absorption. The net transport of galactose was decreased to zero in the absence of Na+ in mucosal and serosal reservoirs. Galactose has been used to induce changes in short-circuit current (delta Isc) across intestine. delta Isc was a hyperbolic function of galactose concentration characterized by the parameters Vmax (maximum change in delta Isc) and Km (concentration needed to attain a velocity equal to half the Vmax).

Effects of a diet lacking HUFA on lipid and fatty acid content of intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle

A feeding experiment was carried out to determine the effect of a diet lacking n-3 and n-6 highly unsaturated fatty acids (HUFA) on lipid and fatty acid content in intestine and gills of male gilthead seabream (Sparus aurata L.) broodstock at different stages of the reproductive cycle: November (pre-spermatogenesis), March (spermatogenesis), and June (post-spermatogenesis). For this purpose, gilthead seabream broodstock were fed either a control diet (C) or an n-3 and n-6 HUFA-deficient diet (D). The results showed no changes in fatty acid content of polar lipids of intestine and gills from fish fed diet C at different stages of the reproductive cycle. However, significant changes were observed in the fatty acid content of neutral lipids in intestine but not in gills in this group. Thus, between November and March, saturates and n-3 HUFA decreased while monoenes increased. In June, the contents of these fatty acids had returned to their initial values (November). Moreover, in fish fed diet D, the fatty acid content of neutral lipid changed in both intestine and gills. In intestine NL, a decrease in saturates and n-3 HUFA and an increment in monoenes were observed from November to June. In gills, a decrease was also observed in n-3 HUFA from NL along the cycle. Nevertheless, n-6 HUFA content remained unchanged. These results show both tissue specificity in seasonal mobilization of fatty acids linked to reproductive processes and the influence of dietary fatty acids on body composition.

Intestinal L-methionine transport in the cultured gilthead bream (Sparus aurata)

Abstract 1. 1. The influx and transepithelial movements of l -methionine and its effects on the electrophysiology and Na-Cl-transport in upper and lower intestine of the cultured fish, Spanis aurata, were measured. 2. 2. The Km and Vmax of l -methionine influx into the tissues were higher in lower intestine than in upper intestine. A prominent diffusion-like transport component was also measured in both segments during influx experiments. 3. 3. Net transepithelial fluxes of l -methionine (1 mM) were observed in both upper and lower intestine, this transport being Na+-dependent. 4. 4. The two intestinal segments exhibited an electrical potential difference (PD) and a short circuit current (Isc) serosa negative or near zero. Tissue conductance (Gt) was higher in posterior than in lower intestine. 5. 5. Addition of l -methionine to the mucosal side of lower or upper intestine did not induce changes in PD in either part. 6. 6. Isotopic fluxes of Cl− or Na+ measurements under short circuit conditions showed that there were no net Cl− or Na+ transport in either part. 7. 7. l -Methionine additions to the mucosa did not induce changes in unidirectional fluxes of Cl− or Na+ or in the (Isc) in either the anterior or posterior intestine.

Sodium chloride absorption across the ileal epithelium of the lizardGallotia galloti

SummaryIon transport processes in the ileum of the lizard,Gallotia (=Lacerta) galloti was examined in vitro by measuring Na22 and Cl36 fluxes across short-circuited preparations.In Ringer-bicarbonate solution there was both a net sodium flux (