The ability of clove oil and MS-222 to minimize handling stress in rainbow trout (Oncorhynchus mykiss Walbaum)

The effects of 60‐mg L^?1 clove oil and 60‐mg L^?1 tricaine methanesulphonate (MS‐222) on the blood chemistry of rainbow trout were compared after exposure to handling stress via caudal puncture blood sampling. Fish sampled by caudal puncture and subsequently exposed to anaesthetics showed a typical handling stress response over a 48‐h period. There were no significant differences between the responses of fish exposed to equal concentrations of clove oil and MS‐222, with the following exceptions: the blood glucose at full anaesthesia, and lactate at full recovery increased significantly in the clove oil‐exposed fish. In a subsequent experiment, the stress response observed in fish sampled by caudal puncture and exposed to clove oil and MS‐222 was compared with a non‐anaesthetized control group. The increases in plasma cortisol levels were significantly lower at recovery in fish treated with either anaesthetic compared with the control fish. Fish exposed to MS‐222 had significantly higher cortisol levels at 1 h. These findings show that few differences exist between the anaesthetic effects of clove oil and MS‐222 on the physiological response of fish to stress. However, clove oil is more effective at reducing the short‐term stress response induced by handling and blood sampling, and is recommended as an alternative fish anaesthetic.     

急性高温胁迫对虹鳟和硬头鳟幼鱼抗氧化酶活性的影响

虹鳟(Oncorhynchus mykiss)与硬头鳟(O.mykiss)为同一种的不同生态型,都属冷水性鱼类.为探讨急性高温胁迫对虹鳟和硬头鳟抗氧化酶活性的影响,选取虹鳟[体重(22.76±2.89)g]和硬头鳟[体重(23.2±1.22)g]幼鱼,分别在不同温度梯度(16℃、20℃、22℃和24℃;16℃、19℃、...     

Plasma growth hormone levels in fed and fasted rainbow trout (Oncorhynchus mykiss) are decreased following handling stress

Plasma growth hormone concentrations of rainbow trout,Oncorhynchus mykiss, fasted for six weeks, were significantly (p < 0.01) higher than in comparable fed animals; in the fasted fish, the levels fell progressively following acute stress (by displacing the fish within their home aquarium), with significant differences from pre-stressed fish evident between one and thirty-two hours after application of the stressor. Plasma growth hormone concentrations also fell significantly in the fed group, but differences were evident only between two and eight hours after stressor application.Plasma cortisol concentrations in pre- and post-stressed fed and fasted fish were similar. There was a bimodal response to stressor application in both groups, with significantly higher values relative to the pre-stressed sample evident one and eight hours after disturbance, but not after two, four or thirty-two hours. The changes in plasma cortisol levels between the initial (09:00h) sample and the sample taken eight hours later resembles the diet pattern seen in trout given access to self-demand feeders.Plasma glucose concentrations in pre-stressed fed animals were higher than in pre-stressed fasted fish. This relationship was also evident between one and four hours and thirty-two hours after stressor application. The post-stress rise in plasma glucose concentration was evident between one and four hours in the fed group, and between four and eight hours in fasted fish.The diel changes in plasma growth hormone and glucose concentrations could not be attributed to normal circadian patterns, and there was no apparent correlation between changes in plasma growth hormone and cortisol concentrations. There was a significant inverse correlation between plasma glucose and growth hormone concentrations when the total data set were analyzed, but these correlations were not apparent when the treatment groups were analyzed separately.     

Lipid-stimulated somatostatin secretion in rainbow trout,Oncorhynchus mykiss

Previous work has shown that somatostatins (SS) affect teleost lipid metabolism indirectly by inhibition of insulin (INS) and directly by stimulation of hepatic lipolysis. In the present study, rainbow trout (Oncorhynchus mykiss) were used to characterize further the lipid-SS relationship by evaluating how lipid, contributes to SS secretion bothin vivo andin vitro. In vivo hyperlipidemia was induced for up to 3 h by short-term (2 min) infusion of a triacylglycerol (TG)-rich lipid emulsion (20% Intralipid^®). Plasma total lipid concentration increased 118 and 155% over control levels 1 h and 3 h, respectively, after infusion; much of this increase was due to elevated plasma fatty acids (FA), which increased 39 and 520%, respectively, over the same time-frame. The hyperlipidemic pattern was attended by a significant increase in the plasma concentration of SS. The specific effects of fatty acids were evaluated on isolated Brockmann bodies. Palmitic acid and oleic acid stimulated SS release 378 and 82%, respectively, over baseline levels. These results indicate that lipids, and in particular fatty acids, modulate SS secretion in rainbow trout.     

Allozyme diversity in Australian rainbow trout, Oncorhynchus mykiss

Rainbow trout, Oncorhynchus mykiss (Walbaum), were first introduced into Australia over 100 years ago, and forms the basis of important recreational inland fisheries and an aquaculture industry in south‐eastern Australia. This paper investigates the genetic variation within and between samples of Australian rainbow trout using allozyme electrophoresis. The levels of genetic diversity within Australia do not show marked differences from those observed in hatchery and wild populations from throughout North America, New Zealand and South Africa, but there is evidence for the loss of some rare alleles during translocation from California to Australia via New Zealand. No appreciable difference in genetic diversity was apparent between hatchery and self‐sustaining wild populations of rainbow trout from mainland Australia. However, significant differences in allelic frequencies were observed, with consistent genetic differences between Victorian and New South Wales samples most likely reflecting state‐based hatchery and stocking policies.     

Effects of dietary nucleotides supplementation on rainbow trout (Oncorhynchus mykiss) performance and acute stress response

This experiment was conducted to examine the effect of dietary nucleotides (NT) on fish performance and acute stress response on fingerling rainbow trout (23 g ± 0.01, mean weight ± SEM). Five experimental diets according to different levels of supplemented nucleotides (0, 0.05, 0.1, 0.15, and 0.2%) were assayed on experimental fish for 8 weeks. Growth, hematological parameters (hematocrit, hemoglobin, erythrocyte, lymphocyte, and neutrophil count), serum proteins (globulin, albumin), and plasma enzymatic activity (alkaline phosphatase, ALP; aspartate transaminase, AST; lactate dehydrogenase, LDH; alanine transaminase, ALT) were assayed. At the end of feeding trial, fish fed the control and 0.2% diets were subjected to handling and crowding stress. Modulatory effects of nucleotides on acute stress response (cortisol and glucose) and plasma electrolytes (Na⁺, Cl⁻, K⁺, and Ca²⁺) were studied. The percentage of body weight gain (WG) and feed efficiency (FE) of fish were better when the fish were fed 0.15–0.2% diets. Fish fed the nucleotide-supplemented diets tended to have lower levels of serum enzymes including ALP, AST, LDH, and ALT. Plasma cortisol levels of fish fed on 0.2% diet under handling and crowding stress were significantly lower than fish fed the control diet at all post-stress time intervals. In our study, fish fed nucleotide-supplemented diet had significantly lower concentrations of glucose compared to those fed the basal diet. The concentrations of sodium, chloride, calcium, and potassium of fish fed the control diet were significantly lower than in fish fed nucleotide-supplemented diet. Dietary nucleotides administration seems to promote growth and to enhance resistance against handling and crowding stress in fingerling rainbow trout.     

Edwardsiellosis in farmed rainbow trout (Oncorhynchus mykiss)

Edwardsiella tarda was isolated from naturally infected rainbow trout (Oncorhynchus mykiss) in raceway culture on a commercial fish farm where the fish were kept at a density of 110 kg m^?3 and at a water temperature of 14°C and with a photoperiod of 13 h light:11 h dark. The clinical signs of diseased fish (150 ± 20 mm standard length) were anorexia and lethargy. The most striking lesions in the fish were in the liver. There were hyperaemia and haemorrhages; on histopathological examination, the liver displayed inflammatory infiltrate in portal area, focal necrosis, dilatation of blood sinus and activation of sinusoidal cells. Infection experiments, performed 2 years after isolation of the original culture of E. tarda, were carried out under laboratory conditions at water temperatures of 15, 18 or 24°C. All experimental fish (common carp, Prussian carp, tench), intraperitoneally injected with 8 × 10⁶ cells, demonstrated a total resistance to E. tarda.     

Cholesterolaemia and triacylglycerolaemia in farmed rainbow trout,Oncorhynchus mykiss

Physiological (reference) value intervals determined by the lower 2.5% and upper 97.5% quantiles were calculated for blood plasma cholesterol (CHOL) and triacylglycerol (TGL) in farmed rainbow trout, Oncorhynchus mykiss, in raceway culture. The fish were given dry pelleted diets that contained 37–47% crude protein and 7–14% crude fat and were kept at a stocking density of 50 kg m^?3 in tanks provided with running freshwater at an ambient temperature of 3–16°C and dissolved oxygen, 8.4–11.5 mg L^?1. Blood was sampled between September and November at a photoperiod of 9:00–13:00 hours: 11:00–15:00 hours (light:dark). Cholesterol levels were significantly (P = 0.0001) greater in males (4.7–12.1 mmol L^?1, n = 34, mean weight 406 ± 138 g) than immature females (3.2–9.7 mmol L^?1, n = 386, mean weight 416 ± 147 g). Physiological range for TGL in immature females and males was 2.4–14.4 mmol L^?1 (n = 249, mean weight 418 ± 149 g). The distribution and density of the quantiles in the tested reference group were made possible by the use of histograms, which showed normal distributions for CHOL in males and in females, but not for TGL, in which a sinistral asymmetry was found. Correlation and regression analyses indicated significant (P = 0.0000) dependence between the CHOL and total protein (r² = 76.2%), CHOL and Fulton's condition factor (r² = 43.3%) and CHOL and absolute weight of liver (r² = 45.5%). Fluctuation in cholesterolaemia and triacylglycerolaemia, depending on nutrition and the aquaculture method is discussed below.     

Expression and characterization of rainbow trout Oncorhynchus mykiss recombinant myoglobin

Fish Physiology and Biochemistry - Recombinant expression system was established for rainbow trout myoglobin (Mb) considering its unique primary structure of having one unusual deletion and two...     

The biliary accumulation of corticosteroids in rainbow trout,Oncorhynchus mykiss,during acute and chronic stress

The accumulation of immunoreactive corticosteroids in the bile of rainbow trout during stress was monitored by radioimmunoassay and GUMS. Although plasma cortisol levels were elevated by confinement for 1 hour, biliary levels of free and conjugated steroids in the bile were unaffected. However, after 24 hours confinement, in addition to elevated plasma cortisol levels, free and conjugated steroids in the bile were also significantly higher than in control, unstressed fish. The time-course of change in plasma and biliary corticosteroid levels was determined in rainbow trout subject to 96 hours confinement stress. Free steroid levels in the bile of stressed fish were elevated within 2 hours of the onset of stress, while levels of conjugated steroids were significantly elevated within 4 hours of the onset of confinement. Analysis of bile from stressed fish, by GC/MS, established the major conjugated steroids present to be tetrahydrocortisone (230 g ml^–1 bile), tetrahydrocortisol (75 g ml^–1), cortisone (33.5 g ml^–1), cortisol (25 g ml^–1) and -cortolone (5 g ml^–1). The data are discussed with reference to the role of cortisone and conjugating enzymes in the clearance of cortisol, and further data are presented to suggest that the analysis of biliary steroid content may provide a suitable means of identifying stressed fish under conditions in which an additional sampling stress is unavoidable.     

Insulin stimulates hepatic lipogenesis in rainbow trout,Oncorhynchus mykiss

The effects of the pancreatic hormones, insulin and glucagon, on rates of lipid biosynthesis in liver removed from rainbow trout, Oncorhynchus mykiss, were evaluated in vitro. Livers were removed from animals fasted for 30–36h, cut into ca. 1 mm³ pieces, and incubated in the presence of various concentrations of salmon insulin (sINS), bovine insulin (bINS), or a combination of BINS and bovine/porcine glucagon (GLU). Lipid synthesis was evaluated by total lipid concentration, ³H₂O incorporation into total lipid, and by fatty acid synthetase activity. Both mammalian and sINS tended to increase tissue total lipid concentration in hepatic tissue incubated for 5h. Insulin also stimulated ³H₂O incorporation into total lipid in a dose-dependent manner. Bovine INS (2 × 10^?6 M) stimulated de novo synthesis nearly 6-fold over control rates; sINS (2 × 10^?6 M) stimulated label incorporation more than 7-fold over control rates. Glucagon inhibited INS-stimulated ³H₂O incorporation; whereas, GLU alone had no effect on lipid synthesis in liver pieces incubated 5h. Lipid class analysis indicated that bINS significantly stimulated ³H₂O incorporation into phospholipids, fatty acids, and triacylglycerols. The greatest accumulation of label was in the triacylglycerol fraction, where incorporation was stimulated 17-fold over control levels. Hepatic enzymatic analysis indicated that bINS also significantly stimulated lipogenic enzyme activity 9-fold above control levels. These results indicate that INS is an important regulator of lipid synthesis in the liver of trout.     

Glucose-stimulated lipolysis in rainbow trout,Oncorhynchus mykiss,liver

Rainbow trout, Oncorhynchus mykiss, were used to characterize further the influence of glucose on hepatic lipolysis. Liver was removed from fed fish, cut into 1 mm³ pieces and incubated for up to 5 h in Hanks medium containing either 2 mM, 5.5 mM, 10 mM, or 25 mM glucose. Glucose-stimulated lipolysis was indicated by tissue triacylglycerol (TG) lipase activity and by medium concentrations of glycerol and fatty acids (FA). Triacylglycerol lipase activity in liver pieces incubated in the presence of higher concentrations (25 mM) of glucose was significantly higher than that in liver pieces incubated in lower concentrations (2 mM) of glucose, rising from 0.075 ± 0.002 (mean ± SEM) nmol FA released/h/mg protein to 0.092 ± 0.004 units. Similarly, higher concentrations of glucose stimulated significantly more FA release and glycerol release from liver pieces than that stimulated by lower concentrations of glucose. Glycerol release from liver pieces incubated in the presence of 10 mM glucose and 25 mM glucose was ca. 2-fold to 2.8-fold, respectively, higher than that from liver pieces incubated in the presence of either 2 mM or 5.5 mM glucose. Fatty acid release from liver pieces incubated in the presence of 10 mM or 25 mM glucose was ca. 1.8-fold higher than that from liver pieces incubated in the presence of either 2 mM or 5.5 mM glucose. Notably, increased glycerol release was not accompanied by a parallel increase in FA. Fatty acid reesterification was more pronounced in liver pieces exposed to higher glucose (10 mM and 25 mM) than in liver pieces exposed to lower glucose (2 mM and 5.5 mM). ¹⁴C-incorporation studies indicated that glucose serves as a carbon source for reesterified FA in trout liver. The route of reesterification appears to be from glucose to glycerophosphate to phosphatidic acid to diacylglycerol to TG. Increasing concentrations of glucose did not affect glycerol kinase activity, indicating that glucose-stimulated lipolysis was not accompanied by increased glycerol recycling within the liver. These results suggest that glucose stimulates fatty acid reesterification and directly enhances net lipolysis in trout liver incubated in vitro.A part of this study was presented at the Annual Meeting of the American Society of Zoologists, December 26–30, 1991, Atlanta, GA.     

Metabolism of exogenous histamine in rainbow trout (Oncorhynchus mykiss)

Information on the metabolism of exogenous histamine in fish is of much concern regarding the effect of dietary histamine on fish. Histamine catabolic enzymes, diamine oxidase and histamine N-methyl transferase were measured in the tissues of rainbow trout. Diamine oxidase was detected in the stomach, pylorus caeca and intestine. Histamine N-methyl transferase was detected only in the liver.A change in the contents of histamine and its metabolites was observed in the tissues of rainbow trout after oral administration of histamine. A large amount of imidazole acetic acid was observed in the serum, kidney, liver and muscle. On the other hand, 1-methyl histamine was detected only in the liver. Histamine and its metabolites, imidazole acetic acid and 1-methyl histamine were metabolized and diminished within 48 hr in all tissues.These results showed that histamine was metabolized by two metabolic routes in rainbow trout. One is the main pathway producing imidazole acetic acid by intestinal diamine oxidase and the other is the complementary pathway producing 1-methyl histamine by liver N-methyl-transferase.     

Nutritional regulation of somatostatin expression in rainbow trout, Oncorhynchus mykiss

Previously we characterized three DNAs from the endocrine pancreas (Brockmann body) of rainbow trout (Oncorhynchus mykiss) that encode for distinct preprosomatostatin (PPSS) molecules: one containing somatostatin-14 and its C-terminus (PPSS I) and two containing [Tyr⁷, Gly¹⁰]-somatostatin-14 at their C-termini (PPSS II′ and PPSS II″). In the present study, the regulation of PPSS expression was studied in rainbow trout placed on varying nutritional regimes (fed continuously, fasted, fasted then refed). Fish that were fasted for one week displayed reduced growth compared to their fed counterparts, but no alteration in pancreatic PPSS expression was noted between the two groups. Fish fasted for 4 and 6 weeks also were growth retarded and displayed increased levels of PPSS I mRNA and PPSS II″ mRNA compared to fed animals; PPSS II′ mRNA levels were not affected by food deprivation. Refeeding fish for two weeks following 4 weeks of food deprivation restored growth and reduced PPSS I and PPSS II″ mRNA expression to levels similar to those displayed by continuously fed fish. Changes in PPSS expression were correlated with increases in plasma SS. These results indicate that nutritional state modulates differential expression of PPSSs. This revised version was published online in July 2006 with corrections to the Cover Date.     

The viability of probiotic bacteria as a factor influencing the immune response in rainbow trout Oncorhynchus mykiss

The objective of the present study was to understand the immune response induced by different forms of the probiont Lactobacillus rhamnosus JCM 1136 in rainbow trout Oncorhynchus mykiss and to clarify the carry over effect after withdrawal of the probiotic diet. A prebiotic-based diet was formulated, which served as the control diet, and to it the selected lactic acid bacteria (LAB) was incorporated in one of the three forms: (1) heat-killed, (2) live-sprayed or (3) freeze-dried. A rearing trial was conducted in triplicate with juvenile rainbow trout (average 126 g), which were fed on the control and three other diets containing the respective forms of the probionts, two times daily until the satiation level for a period of 30 days, following which the test diets were withdrawn and control diet was fed up to 45 days. Sampling was done at 10, 20, 30 and 45 days for gut microflora composition and the non-specific humoral and cellular immune responses of the fish. The viable forms (live spray or freeze-dried) were found to induce better phagocytic activity and complement activity compared to that of the non-viable heat-killed form. The plasma immunoglobulin level showed an increasing trend in the fish groups that received the viable probiont, but the trend did not exist towards the end of the study. Upon withdrawal of the probiotic diets, the LAB disappeared from the intestine and the elevated immune parameters returned to the prefed level. This study elucidates that probiont viability could probably influence the immune responses they induce.     

(革丽)靬金鳟血液学指标的测定

用Botest-3100全自动细胞分析仪首次对革丽革干金鳟血液学指标进行了测定,并与虹鳟和一些鲤科鱼类作了比较.结果显示,由于遗传基础和生理机能的差异,使得革丽靬金鳟与虹鳟和一些鲤科鱼类在血液学指标上也存在一定差异.     

盐度驯化影响虹鳟鳞组织基因表达的转录组分析

合理选择盐度驯化方式是目前虹鳟(Oncorhynchus mykiss)养殖生产所要解决的重要问题之一。本研究通过分析盐度驯化对虹鳟幼鱼外骨骼(鳞组织)中基因表达水平的影响,重点探讨了盐度对鱼类骨代谢的影响机制。首先,分别采集海水(盐度28)驯化7 d和常规淡水养殖(对照)条件下的虹鳟鳞组织,采用Illumina HiSeq 4000测序平台进行转录组测序(RNA-Seq)。以log2|fold change|≥1且P<0.05作为显著差异表达基因(DEGs)筛选条件,共筛选出1714个DEGs,其中,484个基因显著上调,1230个基因显著下调。GO功能注释分析结果显示,上述DEGs主要被注释在细胞膜、细胞质、细胞核、运输、信号转导、金属离子结合和ATP结合等功能中。KEGG通路富集分析结果显示,DEGs在氧化磷酸化、药物代谢–细胞色素P450、蛋白酶体、p53信号通路和心肌收缩等通路中显著富集。利用实时荧光定量PCR (RT-qPCR)对随机选取的8个DEGs的表达量进行验证,结果显示,RT-qPCR与RNA-Seq结果一致,表明RNA-Seq数据可靠。结果表明,以4/d的盐度提升速率对虹鳟进行盐度驯化,对其Mmp-2、Mmp-9、Acp5b、Alpl、Osteocalcin、OPG和Col12a1等骨代谢相关基因及NF-kB、MAPK-(JNK、p38、ERK1/2和STAT3)、Wnt/β-catenin、BMP/Smads和OPG-RANK-RANKL等骨代谢相关信号通路影响不显著,说明本研究所采用的驯化模式较为合理。本研究结果可为虹鳟的养殖生产实践提供参考,所获得的基因信息、功能注释和通路富集信息可为探究硬骨鱼类骨代谢的调控机理及其应对环境变化的演化规律提供新视角。     

Evaluation of fish-meal free diets for rainbow trout, Oncorhynchus mykiss

Eight experimental diets were formulated for rainbow trout using agricultural byproducts as major ingredients. Each experimental diet contained varying amounts of corn grain, corn gluten meal, corn gluten feed and one of the following: 200 g kg^?1 peanut meal, 200 or 400 g kg^?1 soybean meal (SBM), 390 g kg^?1 low-allergen soy flour, 310 g kg^?1 soy protein concentrate, 300 g kg^?1 low-allergen soy protein concentrate or 200 g kg^?1 SBM + 110 g kg^?1 blood meal. One diet contained 200 g kg^?1 SBM and canola oil as the main lipid source. The remaining diets contained 95 g kg^?1 menhaden oil. Fish fed a commercial trout diet exhibited significantly greater weight gain (322%), and a lower feed conversion ratio (0.89) but significantly lower protein efficiency ratio (2.18) than fish fed the experimental diets. Within the experimental diets, fish fed the 400 g kg^?1 soy flour diet and the 400 g kg^?1 soybean meal diet had significantly higher weight gains (276% and 268%) and protein efficiency ratios (2.58 and 2.52), and lower feed conversion ratios (1.02 and 1.03) than fish fed other experimental diets. Fillet flavour varied between treatments. Most notable was the lower fishy flavour and higher chicken flavour of fish fed the diet that contained canola oil rather than menhaden oil. Microscopic evaluation of the liver and five sections of the gastrointestinal tract failed to demonstrate any differences between treatment groups. The ingredient costs of several experimental diets were lower than the estimated cost of a standard commercial trout diet. However, the superior feed conversion ratios of fish fed the control diet resulted in lower feed costs per unit of fish produced.