A releaser pheromone that attracts methyltestosterone- treated immature fish in the urine of ovulated female rainbow trout

SUMMARY: Behavioral experiments concerning a releaser pheromone in the urine of female rainbow trout were performed using immature fish administered orally with 17α-methyltestosterone (MT) during the non-spawning season. The urine was collected by catheter. The frequency of entries of test fish was recorded in each channel scented by test and control solutions in a Y-maze trough. The behavior of both MT-treated and control fish demonstrated that they could not discriminate the differences between distilled and environmental water as control solutions. There was also no difference between MT-treated and control fish when distilled and environmental water were introduced. The MT-treated immature fish were attracted to the channel scented by ovulated female urine. Neither coelomic fluid nor the immature female urine had any effect on the behavioral responses of MT-treated fish, while immature control fish had no preference for the urine of ovulated females. These results suggest in rainbow trout that ovulated female urine contains a releaser pheromone to attract mature males, and that androgens are involved in the sensory mechanisms detecting the releaser pheromone in fish.     

Purification and characterization of hepatic triacylglycerol lipase isolated from rainbow trout,Oncorhynchus mykiss

Trialcylglycerol (TG) lipase was isolated and partially purified from rainbow trout liver. Triacylglycerol lipase activity was assayed by measuring¹⁴C-oleic acid release from¹⁴C-triolein.¹⁴C-oleic acid release was linear for up to two hours. Optimal activity occurred at pH 7.0 and 15°C. Most of the lipase activity was recovered in the cytosolic fraction. A 27,000-fold purification was achieved after Sepharose (Bio-gel A 0.5 M, 200–400 mesh) chromatography of a resuspended 20% ammonium sulfate fraction. The molecular weight of the trout hepatic lipase as determined by size-exclusion chromatography and by SDS-polyacrylamide gel electrophoresis was 40–43 kD. Lipase-mediated hydrolysis of TG resulted in the production of diacylglycerols, monoacylglycerols, and fatty acids. Kinetic analysis indicated that V_max=0.016 nmol/h/mg protein and that K_m=0.28 mM triolein. Lipolytic activity was enhanced in the presence of cAMP/ATP-Mg²⁺. These results suggest that the liver of trout possesses a neutral TG lipase that is responsible for mobilizing stored TG and is catalytically activated by phosphorylation.A part of this work was presented at the Annual Meeting of the American Society of Zoologists, December 26–30, 1990, San Antonio, TX.     

Occurrence and prevalence of infectious pancreatic necrosis virus in rainbow trout (Oncorhynchus mykiss) cultured in cages in the Black Sea

Rainbow trout (Oncorhynchus mykiss) cultured in cage systems in the South Eastern Black Sea were surveyed for the type, occurrence and prevalence of infectious pancreatic necrosis virus (IPNV). Two nearby farms (designated as Farm A and Farm B) were visited monthly in 2007 and 2008. At each farm, 385 fish were selected randomly from five cages. Another farm with infected trout from a hatchery also was monitored for IPNV from the transfer to harvest. IPNV was found to be prevalent in both farms surveyed. In Farm A, IPNV was present throughout the growing period, from January to May, and all five randomly sampled cages tested positive for IPNV in March and April of 2007. In Farm B, IPNV was present only in February and March in 2007, and in 2008, IPNV was observed in January (two cages) and February (one cages) at low levels. Interestingly, IPNV was absent 2 weeks after transfer to the sea at 17.5°C. The same strain of IPNV, genotype III that was isolated from the same stock of fish at the hatchery, reoccurred when water temperatures dropped to 12°C in December in the Black Sea. Transferring fish to the sea at high water temperatures could lessen the negative impacts of IPNV on growth of rainbow trout in brackish water.     

植酸酶对金鳟体成分及金鳟椎骨中钙、磷含量的影响

采用喷涂法和预处理两种方法,在豆粕型金鳟饲料中添加不同浓度的植酸酶,通过90 d的饲喂试验,研究植酸酶对金鳟(Oncorhynchus mykiss Walbaum)体成分及其椎骨中钙、磷含量的影响。结果显示:喷涂法和预处理法添加植酸酶的处理组与对照组相比,粗蛋白、粗脂肪的含量均有所下降;喷涂法添加植酸酶的处理组的鱼体粗灰分、磷和钙含量均高于对照组,其中,喷涂法添加1500 U/Kg植酸酶组鱼体磷含量、灰分含量和钙含量显著高于对照组(P(0.05),且此组鱼体磷高于其它试验组;喷涂法各组椎骨中粗灰分、磷含量较对照组提高显著(P(0.05),2500 U/kg植酸酶组椎骨磷含量最高,椎骨中钙含量除D1和D8组外,添加植酸酶的处理组均较对照组提高显著(P(0.05)。预处理法添加植酸酶的处理组与对照组相比,鱼体和椎骨中粗灰分、磷和钙含量均有显著提高(P(0.05),但植酸酶试验组间椎骨中粗灰分、磷含量和钙含量差异均不显著(P(0.05)。结果表明,金鳟饲料喷涂法添加植酸酶1500~2500 U/kg浓度最适,预处理法添加植酸酶500 U/kg浓度较为宜。     

Distribution and induction of cytochrome P450 1A1 in the rainbow trout brain

Cytochrome P450 (CYP) 1A1 participates in the activation as well as detoxification of environmental pollutants such as aromatic hydrocarbons. This CYP form is also efficiently induced by aromatic hydrocarbons. The presence of CYP 1A1 in the brain might thus be of physiological and toxicological importance. In the present investigation on rainbow trout, the distribution of 7-ethoxyresorufin-O-deethylase (EROD) activity, a cytochrome CYP 1A1 catalyzed reaction, was measured in whole tissue homogenates from brain parts. In control fish, a relatively high activity was found in the rainbow trout olfactory bulb compared to the other brain parts. Although an EROD induction (3 to 7-fold) by β-naphthoflavone (BNF) was recorded in all brain parts from the rainbow trout, the highest induced activity was measured in the olfactory bulbs. To ascertain the distribution of EROD activity in cells, whole brain tissue was subfractionated by differential centrifugation. The fractionation scheme separated mitochondria (P2 fraction) and microsomes (P3 fraction) as determined by marker enzymes and electron microscopy. In control rainbow trout, a low EROD activity could be measured in the P2 fraction. BNF induced the EROD activity in both P2 and P3 fractions. Western blotting showed the induction by BNF of a protein band in the P2 and P3 fractions with a molecular mass around 58,000 when highly specific anti-cod CYP 1A1 antibodies were used. ELISA measurements confirmed the induction of CYP 1A1 protein in the rainbow trout brain subcellular fractions.     

Enhancing highly unsaturated ω‐3 fatty acids in phase‐fed rainbow trout (Oncorhynchus mykiss) using Alaskan fish oils

Rainbow trout, average weight 185–187 g, were fed feeds containing menhaden oil, canola oil or fish oils (pollock, pink salmon or rockfish) produced from Alaskan seafood processing waste as the added oil for 8 weeks, at which time the fish weighed 391–411 g (average 404 g, pooled SE = 5.7). The fish were previously fed from 75 g average weight fed commercial feed containing poultry oil as the added oil. No significant differences were measured in final weight or feed conversion ratio among dietary treatment groups. Significant differences were found in fillet ω‐3 fatty acid (FA) levels from fish receiving fish oil‐supplemented feeds compared to those from fish receiving feeds containing canola oil. Fillet contents of eicosapentaenoic acid (EPA; 20:5ω3) and decosahexaenoic acid (DHA; 22:6ω3) were highest in the pollock oil treatment group, although all fish oils increased highly unsaturated ω‐3 FA contents (mg 100 g^?1) of fillets. Fish oil used through the production cycle was reduced by 25% by supplementing feeds with poultry oil during the middle phase of production (75–175 g) compared to using feeds containing fish oil throughout the production cycle. Fish oils recovered from Alaskan seafood processing waste were suitable alternatives to conventional fish oil as ingredients in rainbow trout production feeds.     

Phenotypical parameters as a tool to evaluate the immunostimulatory effects of laminarin in Oncorhynchus mykiss

Laminarin is a β‐glucan from the brown algae Laminaria digitata (J.V. Lamour), which can activate innate immune responses. With the aim of developing a strategy to evaluate specific phenotypical parameters of the effects of laminarin in trout innate immunity, we (i) fed fish with laminarin‐supplemented diet (0.2 g kg^?1 day^?1) for 21 days and (ii) treated fish with a single dose of intraperitoneal injected laminarin (0.08 g kg^?1 fish). The evaluation of cellular and humoral immune parameters was established at phenotypic level by the phagocytic activity of headkidney macrophages and detection of inflammatory cytokines in head kidney and gill tissue by indirect ELISA. Results showed that both delivery methods of laminarin produce an increase in the phagocytic activity in head kidney macrophages and a significant increase in the production of TNFα and IL‐8 in gill tissue at day 21. Additionally, some of these parameters were significantly correlated (P < 0.025), which places them as new potential combined markers to detect activation of trout defense mechanisms by laminarin. These results highlight the importance of developing new protocols to quantitate immune parameters, in order to evaluate immunostimulants in fish farming.     

Evolutionary implications of two rainbow trout growth hormone genes

The primary structures of two rainbow trout growth hormone mRNAs (GH1 and GH2) have been deduced by direct sequencing of their respective cDNA clones and portions of the mRNA. Both GH1 and GH2 mRNA contain open reading frames comprised of 630 nucleotides and encode 210 amino acid residues of which 11 are variant. The translated regions of both mRNA are flanked by a short but rather conserved 5′-end, and a relatively long but highly diverged 3′-end. The differences at translated and 3′-untranslated regions suggest that the GH1 and GH2 mRNA originate from different loci. The GH1 and GH2 mRNA are likely transcribed from two distinct loci which were duplicated during tetraploidization of salmonid genome between 50 to 100 million years ago. The GH2 gene has been isolated and sequenced from a rainbow trout genomic library. This gene spans a region of approximately 4 kilobases. The trout GH gene is comprised of 6 exons and 5 introns, in contrast to 5 exons and 4 introns in mammals. The additional intron in the trout gene interrupts the translated regions that are analogous to the last exon of the mammalian counterpart. The alleged internally repeating sequences in mammalian GH, prolactin (Pr1) and placental lactogen (PL) are not observed in the predicted polypeptide sequence of trout GH. In addition, direct repeats that flank exons I, III and V of mammalian GH, Pr1 and PL genes are absent in trout gene. These findings indicate that the rainbow trout GH gene structure does not support the current hypothesis that internally repeated regions in GH, Pr1 and PL arose from a small primordial gene.     

Rainbow trout (Oncorhynchus mykiss,Walbaum ) develop a more robust body shape under organic rearing

Prolonged exposure to captive conditions has led to the development of a rainbow trout ‘farmed’ phenotype, which is different from that of wild trout. Selection for desirable productive traits in hatcheries has resulted in the development of some morphological traits that are maladaptive in nature. The recent development of organic aquaculture, guided by the well‐being of the fish, could potentially produce a new farmed phenotype that would be more adaptive in nature. In this study, rainbow trout reared in intensive and organic farms were compared by means of shape analysis, to detect patterns of shape variation associated with rearing environment. The results of this study highlight a significant effect of the rearing method on rainbow trout shape: organically reared trout showed a higher body profile, in particular in the head and trunk regions, shorter median fins and a deeper caudal peduncle. A combined effect of density and habitat complexity could have contributed to the observed shape differences: in organic rearing systems, lower densities and steady water could increase territoriality and aggressive interactions, promoting body designs more functional in rapid attacks and escapes.