刀鲚POMC基因的cDNA克隆及其应激应答

为了研究刀鲚(Coilia nasus)阿黑皮素原(proopiomelanocortin,POMC)基因的应激应答及调控,克隆了刀鲚POMC基因的c DNA全长。刀鲚POMC基因的c DNA全长2030 bp,编码区699 bp,编码232个氨基酸。二级结构预测显示,刀鲚POMC包括信号肽(signal peptide)、N末端区(N-terminal region,NPP)、促肾上腺皮质激素结构域(adrenocorticotropic hormone,ACTH)、β-脂解素(β-LPH)、α-促黑素(α-MSH)、促肾上腺皮质激素样垂体中叶多肽(CLIP)、γ-脂解素(γ-LPH)、β-促黑素(β-MSH)和β-内咖肽(β-EP)结构域。运用荧光定量的方法检测了该基因在刀鲚不同组织中的表达分布。结果显示,POMC在健康刀鲚的脑高表达,鳃、肾、精巢相对高表达,肝、脾、肠、头肾、肌肉和卵巢中微量表达。运输胁迫后,POMC基因的表达量显著下降(P0.05);10‰ NaCl组4 h和6 h POMC基因的表达量显著上调(P0.05),6 h的表达量恢复至应激前。POMC基因在脂肪代谢及应激调控中发挥重要的功能,本研究结果可为该基因在刀鲚后续育种及应激调控工作提供重要基础。     

刀鲚PPARγ基因的cDNA克隆及其应激应答

旨在研究刀鲚(Coilia nasus)过氧化物酶体增殖物激活受体γ(peroxisome proliferator activated receptor, PPARγ)基因的应激调控表达,克隆并获得了刀鲚PPARγ基因的cDNA全长。刀鲚PPARγ基因的cDNA全长1951 bp,开放阅读框1470 bp,预测编码489个氨基酸。刀鲚PPARγ包括4个功能结构域,即A/B区, DNA结合区(DNA binding domain, DBD区),铰链区,配体结合区(ligand binding domain, LBD区)。运用荧光定量PCR (real time quantitative PCR, RT-qPCR)检测刀鲚PPARγ基因在不同组织、运输胁迫和胚胎发育时期的表达。结果显示,刀鲚PPARγ在各组织中均有表达,其中在肝中表达量最高,在脑、肠、心脏、肾、头肾、肌肉中相对高表达,在鳃和脾中微量表达。运输胁迫过程中, PPARγ基因表达显著上调(P0.05),在4 h达到峰值,随后显著降低,但仍高于对照组。PPARγ在胚胎发育时期各时期均表达,其中在受精卵时期高表达,随后表达量急剧降低,并在此后的时期一直处于较低的表达水平。PPARγ基因在应激过程中发挥重要作用,也是胚胎发育过程中重要的基因。本研究为刀鲚的人工繁育和应激调控提供了理论基础。     

高碳水化合物日粮对异育银鲫血浆皮质醇含量和HSP70基因mRNA表达的影响

为了探讨高碳水化合物饲料是否会引起异育银鲫(Carassius auratus gibelio)的应激反应,选用体质量为(35.60±1.11)g的异育银168尾,随机分成2组,一组设为对照组(NS),投喂碳水化合物水平为35％的日粮；另一组设为高碳水化合物实验组(HS),投喂碳水化合物水平为50％的日粮,每组3个重复.在控温的循环水系统中饲养35 d和70 d后,测定异育银鲫血浆皮质醇激素含量及其肝、心脏、脾、肾中HSP70基因mRNA的表达量.结果显示,高碳水化合物实验组35 d时血浆皮质醇激素与对照组相比较显著升高(P＜0.05),肝和心脏HSP70基因mRNA表达较对照组明显增强(P＜0.05)； 70 d时血浆皮质醇激素含量升高,且70 d时高碳水化合物组肝、心脏、脾和肾HSP70基因mRNA表达与对照组相比全部增强.各组饲养70 d后,饥饿24 h后重新投喂的0h、6h、12h、24 h、48 h,高碳水化合物实验组(HS)皮质醇含量在6h、48 h显著高于对照组(P＜0.05),在6h、12h、48 h肝HSP70基因mRNA表达与对照组相比均增强(P＜0.05),说明异育银鲫对50％碳水化合物含量的饲料的耐受性比较差,鱼体产生了应激反应.结果说明,当异育银鲫血清皮质醇激素含量升高时,其肝中HSP70基因mRNA的表达量却降低,反之亦然.本研究旨在为水生动物营养应激及营养免疫的相关研究提供新的思路,为开辟鱼类应激的营养调节提供科学依据.     

岩原鲤MSTN基因克隆及饥饿对MSTN表达的影响

运用同源克隆的方法获得岩原鲤(Procypris rabaudi(Tchang))肌肉生长抑制素(myostatin,MSTN)c DNA全长序列,并通过逆转录PCR(RT-PCR)检测MSTN基因的组织差异性表达以及饥饿胁迫对MSTN基因表达的影响。结果显示,岩原鲤MSTN基因1 547 bp的c DNA序列,编码区为1 128 bp,编码375个氨基酸。PCR检测显示,该基因在肌肉和脑组织中大量表达,在眼、肠、心、鳃、肾和头肾组织中少量表达,在肝胰脏、脾脏组织中未见表达。饥饿再投喂实验表明肌肉组织中MSTN基因表达含量随着饥饿时间的延长逐渐升高,恢复投喂后3d表达含量急剧下降,投饵后6 d升至正常水平。结果表明,MSTN的表达对营养摄入敏感,在饥饿状态下岩原鲤通过上调MSTM表达来抑制肌肉生长,节约能量消耗。     

低氧胁迫对鲢心肌细胞凋亡及其调控基因Bax、Bcl-2表达的影响

为了解低氧胁迫对鲢心脏的损伤及其机制,检测了不同低氧条件下鲢血清肌酸激酶(CK)活力和心肌细胞凋亡情况及凋亡调控基因Bax、Bcl-2的表达。结果显示:低氧胁迫下血清CK活性显著升高,表明低氧实验中鲢心肌细胞可能受到了损伤;TUNEL检测显示低氧胁迫鲢心肌细胞发生了凋亡,且随着氧浓度的下降凋亡指数升高,组间差异极显著;qPCR显示,鲢心肌Bax基因和Bcl-2基因变化趋势相反,Bax基因随着处理时间的延长,氧浓度的下降,表达量升高,Bcl-2基因表达量降低,且实验结束时与常氧对照值(Normoxia group,NO)比较差异显著。结果表明,低氧胁迫通过升高鲢心肌Bax基因表达、降低Bcl-2基因表达,导致心肌细胞凋亡,从而造成鲢心脏损伤甚至鱼死亡。     

急性胁迫对团头鲂铁稳态及其相关基因表达的影响

为研究急性应激反应对鱼体铁含量及铁稳态相关基因的影响,以团头鲂为研究对象,通过腹腔注射皮质醇来模拟急性应激,在注射后不同时间点对团头鲂的血液、肠和肝脏进行取样,采用分光光度法测定血清和肝脏中的铁含量,采用实时荧光定量PCR对铁稳态相关基因的表达量进行检测。结果显示,皮质醇注射后血浆皮质醇显著升高,血浆中铁含量在4、8、10和12 h显著高于对照组,而肝脏中的铁含量在4、8、10和12 h时显著低于对照组。团头鲂肝脏中铁调素(hep)基因表达量显著增加,并分别在8和10 h达最大值,随后有所下降。肠道和肝脏中转铁蛋白基因(Tf)的表达量均呈先升高后下降的趋势。研究表明,急性应激下机体细胞内储存铁大量释放到体液中,造成病原感染和体内增殖风险增加;hep及Tf上调表达降低细胞内铁释放和促进体液铁向胞内蓄积,在鱼体内铁稳态的调控和固有免疫反应中发挥着重要的作用。     

二氧化碳麻醉对鲢生理生化指标及神经调控相关基因表达的影响

为研究CO 2麻醉对鲢(Hypophthalmichthys molitrix)的生理效应及其作用机制,设置充CO 2、充O 2实验组,并以持续充空气作为对照组,分别测定鲢的生理生化指标、神经递质含量和神经调控相关基因表达变化。结果显示:与对照组比较,CO 2麻醉处理后,鲢呼吸频率降低37%,血清K+浓度显著升高4倍,肝糖原含量降低86.96%,血清中乳酸、尿素氮浓度分别升高1.08和1.57倍。以上指标在充O 2处理下变化趋势与充CO 2处理下相似,但是测定值高于充CO 2处理组。CO 2处理组血清皮质醇水平无显著变化,但充O 2处理组皮质醇显著升高2.41倍;CO 2处理组的脑组织多巴胺和5-羟色胺水平下降。qPCR结果显示,CO 2麻醉后脑组织双孔K+通道蛋白kcnk3a、kcnk9和缺氧相关hif-1α和epo基因表达量均升高。结果表明,CO 2麻醉鲢可以有效降低新陈代谢和应激反应,是一种安全、有效的麻醉方法。     

亚硝酸盐氮胁迫对鳙血液生化指标以及组织HSP70 mRNA表达水平的影响

为了探讨亚硝酸盐氮胁迫对鳙[初均重:(180.05±0.092)g]血液生化指标和组织热休克蛋白70基因表达水平的影响,实验选用170尾鳙,暴露于48.634 mg/L亚硝酸盐氮96 h后,进行96 h恢复实验。并在胁迫0、6、12、24、48、72和96 h以及恢复12、24、48、72和96 h时采集样品。结果显示,胁迫6 h后,血清皮质醇含量和谷丙转氨酶活性显著升高;胁迫12 h后,血清中葡萄糖含量显著升高;胁迫24 h后,血清总胆固醇含量开始显著降低;胁迫48 h后,血清总蛋白和甘油三酯含量开始显著降低,三碘甲状腺原氨酸含量和谷草转氨酶活性则显著升高;胁迫72 h后,血清低密度脂蛋白和高密度脂蛋白含量开始显著降低。恢复96 h后,鱼体血清生理指标大多都已恢复至胁迫前水平,而组织热休克蛋白70 mRNA表达水平的差异显示,头肾抗亚硝酸盐氮响应最快,其次为鳃和肠道,而脾脏热休克蛋白70 mRNA表达水平在恢复12 h时显著升高;恢复96 h后,除鳃组织外,肾脏、肠道和脾脏的热休克蛋白70 mRNA表达量均恢复至胁迫前水平。研究表明,亚硝酸盐氮对鳙的蛋白质代谢、脂质代谢和糖代谢均产生影响,并且诱导部分组织热休克蛋白70 mRNA的表达,而鳙对水体中高浓度的亚硝酸盐氮应激6 h即可产生快速应答,并启动防损伤自我保护机制,促进新陈代谢水平,保护机体免受应激损伤。     

注射LHRH-A2对刀鲚的催产效果及其雌鱼血液生化指标的影响

为了丰富刀鲚人工繁殖理论,探明LHRH-A2对刀鲚的催产效果及其雌鱼血液生化指标的影响,本研究以2冬龄人工养殖刀鲚为研究对象,通过注射LHRH-A2进行人工催产,并分析催产效果;同时应用放射性免疫、化学发光等方法,对人工催产过程中刀鲚雌鱼的血液生化指标进行了系统研究。结果显示,按照雌鱼30μg/kg、雄鱼减半的剂量注射LHRH-A2,刀鲚亲鱼死亡率为16.67%±3.34%;存活刀鲚亲鱼群体中,效应时间为21~24 h,催产率为83.33%±3.34%,受精率为75.06%±6.19%。注射催产素21 h内,血浆中17β-雌二醇(17β-estradiol,E2)、催乳素(prolactin)、甲状腺素(thyroxine,T4)、皮质醇(cortisol)、总蛋白(total protein,TP)、乳酸(lactate)在人工催产过程中表现出先上升后下降的规律;三碘甲腺原氨酸(three iodine thyroid,T3)、甘油三酯(triglyceride,TG)、Cl–呈现持续下降趋势;谷丙转氨酶(alanine transaminase,ALT)、谷草转氨酶(aspartate transaminase,AST)、渗透压(osmotic pressure)、K+、Na+呈现持续上升的趋势。比较以上血浆指标在产卵组和未产卵组的实验结果,产卵组形成高皮质醇、TP、TG、渗透压、Na+、K+的血浆环境和低E2、催乳素、乳酸、T4、T3、Cl-、ALT、AST的血浆环境,而未产卵组的这些指标与产卵组相反。结果表明,人工催产过程对肝脏、肾脏等正常功能造成了影响,从而抑制催产素LHRH-A2对卵子的正向调控作用。本研究初步揭示了人工催产应激对刀鲚雌鱼成功排卵的影响机制,为进一步优化刀鲚的规模化人工繁殖提供科学依据。     

长江刀鲚鱼种驯食浮性颗粒饲料试验研究

采用灯光诱鱼协同缓沉饲料驯食过渡至浮性颗粒饲料投喂的方法,高密度驯养长江刀鲚(Coilia nasus)鱼种,建立了8~10 cm刀鲚鱼种转食浮性颗粒饲料的人工饲养技术,为刀鲚的集约化养殖提供技术支撑。结果显示,经16 d的驯食,刀鲚在投饵后1 h之内吃完饲料,驯食期间刀鲚平均成活率为75.05%。闪光诱鱼比常光诱鱼更利于刀鲚鱼种驯食浮性颗粒饲料;先期对浮性颗粒饲料处理成缓沉投饲驯食并逐步过渡至完全摄食浮性颗粒饲料的操作能让刀鲚鱼种在短期内(16 d)完全摄食浮性颗粒饲料。     

肌醇对氨氮应激下团头鲂幼鱼免疫的影响

为了研究氨氮应激下肌醇对团头鲂幼鱼免疫的影响,实验选择初均重为(3.40±0.07)g的健康团头鲂幼鱼450尾,随机分为6组,每组3个重复,分别投喂含肌醇0、101.2、202.3、404.8、809.1和1 616.4 mg/kg的精制饲料,实验期为90 d。结果表明:与对照组相比,氨氮应激前,404.8 mg/kg肌醇添加组显著提高了团头鲂幼鱼淋巴细胞百分比、补体3、补体4和血液呼吸爆发活性(P0.05);氨氮应激12 h,404.8和809.1 mg/kg肌醇添加组的血液白细胞、红细胞、淋巴细胞百分比、血红蛋白和血清补体3、补体4水平显著升高(P0.05),皮质醇水平显著降低(P0.05),202.3和404.8 mg/kg肌醇添加组的血细胞呼吸爆发活性显著提高(P0.05);氨氮应激72 h,404.8 mg/kg肌醇添加组的血液白细胞、红细胞、淋巴细胞百分比、血红蛋白、血清补体3和血细胞呼吸爆发活性显著升高(P0.05),皮质醇水平显著下降(P0.05),809.1 mg/kg肌醇添加组的血清补体4水平显著升高(P0.05)。研究表明,饲料中添加适量的肌醇(404.8 mg/kg)即可增强团头鲂幼鱼的免疫力,对团头鲂幼鱼抗氨氮应激起到了一定的保护作用。     

Stress hormones and the cellular stress response in salmonids

The relationship between stress protein (SP) levels and the hormonal stress response in salmonids was examined through the measurement of gill SP70 and SP30 levels together with plasma cortisol, glucose and ion concentrations, in response to handling stress (45 s holding in a net), intraperitoneal cortisol implants, and heat shock (+10 °C). Handling and cortisol implants resulted in increased plasma cortisol and glucose levels. Heat shock following handling reduced plasma [Na⁺] below that observed in response to the handling stress alone, and heat shock following cortisol implant significantly lowered both plasma [Cl^–] and [Na⁺] below that of fish receiving the cortisol implant alone. Increased SP70 levels occurred 1 h following the 2 h +10 °C heat shock. Handling the fish prior to the application of heat shock suppressed the increase of SP70 levels in the gills. However, increased plasma cortisol concentrations alone did not attenuate gill tissue SP70 increase caused by heat shock. Physiological (10^–7 M) and pharmacological (10^–5 M) concentrations of adrenaline caused increased levels of SP70 in hepatocytes. Addition of the -blocker propanolol blocked this response to adrenaline. The results indicate that handling procedures do not result in an increase of hsp30 or hsp70 and may suppress hsp synthesis under certain circumstances.     

Effect of L‐tryptophan supplemented diets on serotonergic system and plasma cortisol in Totoaba macdonaldi (Gilbert, 1890) juvenile exposed to acute stress by handling and hypoxia

Brain serotonin and cortisol play a central role in integrating the neuroendocrine response to stress. Previous studies in aquatic species show that dietary supplementation with the 5‐HT precursor L‐tryptophan amino acid is able to modulate this response. The aim of this study was to evaluate the effect of dietary tryptophan (Trp) on the serotonergic system and acute stress response in Totoaba macdonaldi. Four groups of fish were fed with one of four isonitrogenous and isocaloric diets formulated with different Trp content: 0.5% (1X TRP, control diet), 1.1% (2X TRP), 1.7% (3X TRP) and 2.3% (4X TRP). After a feeding period of 21 days, groups were exposed to acute stress by handling with a net or hypoxia. Feeding with Trp‐enriched diets resulted in increased 5‐HT content in telencephalon of undisturbed fish. Handling increased the 5‐hydroxyindole acetic acid (5‐HIAA) and serotonin turnover (5‐HIAA/5‐HT) in telencephalon of fish fed with 1X TRP and 2X TRP but was not significant for the fish fed 3X TRP and 4X TRP, and no significant increase was observed by hypoxia in both telencephalon and hypothalamus in any of the diets. An inverted U‐shaped response was observed in plasma cortisol increasing with 2X TRP after both handling and hypoxia and decreasing with diets rich in Trp, 3X TRP and 4X TRP. A higher increase was observed in haematocrit, plasma glucose and lactate in hypoxia than the handling groups. Our results indicate that Trp supplementation modulated cortisol response and mediated negative feedback of 5‐HT system in telencephalon after acute stress.     

Effects of chronic confinement on physiological responses of juvenile gilthead sea bream, Sparus aurata L., to acute handling

Understanding how gilthead sea bream, Sparus aurata L., an important Mediterranean Sea species for aquaculture, respond physiologically to stressors commonly encountered in intensive rearing is important for effective production, as managing for stress is a major factor in maintaining healthy fish stocks. Our objective was to determine whether holding juvenile gilthead sea bream at a high density (HD), as a chronic stressor, would affect their physiological responses to a subsequent acute handling stressor. After acclimation at a low density (LD) of 6 kg m^?3 in 200‐L circular tanks containing 33–36 g L^?1 recirculating seawater at 19°C under a normal photoperiod, juvenile 37‐g gilthead sea bream were confined for 14 days at a HD of 26 kg m^?3 and then subjected to 30‐s aerial emersion in a dipnet. Plasma levels of cortisol, glucose, lactate, osmolality and chloride were determined in fish held in separate lots during LD (control) and HD confinement at 0, 1, 2, 7 and 14 days, and then after handling at 0, 1, 2, 4 and 8 h. Although plasma cortisol levels were similar in LD and HD fish groups after 14 d of confinement (15 and 23 ng mL^?1, respectively), the cortisol response in fish from the HD treatment at 1 and 2 h following acute handling (70 and 37 ng mL^?1, respectively) was only about half of that measured in the control group (139 and 102 ng mL^?1); plasma cortisol was similar in both groups by 4 and 8 h. In contrast, plasma glucose elevations in response to handling were higher at 4 and 8 h in the HD‐held fish (94 and 72 mg dL^?1, respectively) than in those from the LD treatment (59 and 51 mg dL^?1); glucose responses were similar in both groups at 1 and 2 h after handling and throughout confinement. Plasma lactate levels were higher in LD fish than in the HD group at the beginning of the experiment but were similar after 14 d confinement and responses to handling were similar (e.g. 33 and 35 mg dL^?1 at 1 h). Plasma osmolality showed increases during the first 2 h after acute handling but no differences were evident between the two density treatments at any time during confinement or posthandling. Plasma chloride levels did not change throughout the experiment. The reduced plasma cortisol response to acute handling likely resulted from negative feedback of mildly but chronically elevated circulating cortisol caused by the confinement stressor on the hypothalamic–pituitary–interrenal axis. While other post‐handling physiological changes also showed differences between treatment groups, the suppressed cortisol response in the HD‐held fish suggests a reduction in the gilthead sea bream's normal capacity to respond to an acute stressor.     

Stress in African catfish (Clarias gariepinus) following overland transportation

Of the many stressors in aquaculture, transportation of fish has remained poorly studied. The objective of this study was therefore to assess the effects of a (simulated) commercial transportation on stress physiology of market-size African catfish (Clarias gariepinus). Catfish weighing approximately 1.25 kg were returned to the farm after 3 h of truck-transportation, and stress-related parameters were measured for up to 72 h following return. Recovery from transportation was assessed through blood samples measuring plasma cortisol, glucose and non-esterified fatty acids (NEFA) and gill histology. Also, the number of skin lesions was compared before and after transport. Pre-transport handling and sorting elevated plasma cortisol levels compared to unhandled animals (before fasting). Plasma cortisol levels were further increased due to transportation. In control fish, plasma cortisol levels returned to baseline values within 6 h, whereas it took 48 h to reach baseline values in transported catfish. Plasma glucose and NEFA levels remained stable and were similar across all groups. Transported catfish did not, on average, have more skin lesions than the handling group, but the number of skin lesions had increased compared to unhandled animals. The macroscopic condition of the gills was similar in control, transported and unhandled catfish; however, light microscopy and immunohistochemistry revealed atypical morphology and chloride cell migration normally associated with adverse water conditions. From our data, we conclude that transportation may be considered a strong stressor to catfish that may add to other stressors and thus inflict upon the welfare of the fish.     

Growth, immune function, and disease and stress resistance of juvenile Nile tilapia (Oreochromis niloticus) fed graded levels of bovine lactoferrin

Juvenile Nile tilapia (Oreochromis niloticus) were fed nutritionally complete, practical basal diets supplemented with bovine lactoferrin (Lf) at 0, 200, 400, 800, or 1600 mg/kg diet to apparent satiation twice daily for 8 weeks. After the feeding trial, the effect of dietary Lf on growth performance, immune function, and resistance to Streptococcus iniae challenge and low-water stress was determined. Dietary Lf did not affect growth performance (weight gain, feed intake, feed efficiency ratio, or survival) or haematological parameters (haemoglobin, white and red blood cell counts, or haematocrit) (P > 0.05). Crowding stress produced significant increases in plasma cortisol, glucose, lactate, and osmolality from baseline values (P ≤ 0.001), but dietary Lf did not affect plasma glucose, osmolality, or cortisol concentrations (P > 0.05). The level of Lf in diet had a significant impact on survival following S. iniae challenge with fish fed the 800 mg/kg Lf diet having significantly higher survival than control fish (P ≤ 0.05). There was not a corresponding increase in activity of non-specific or specific immune parameters (plasma lysozyme and spontaneous haemolytic complement activities or agglutination antibody titer against S. iniae) with addition of Lf to diets (P > 0.05), but plasma iron decreased and total iron binding capacity (TIBC) increased significantly with increasing concentration of Lf in diet (P ≤ 0.05). The ability of Lf to sequester iron, an essential nutrient required for the growth of bacteria, is regarded as one of its key antibacterial properties. The increased survival with increasing dietary concentration of Lf seemed to correspond with a decrease in plasma iron concentration and not enhancement of non-specific or specific immune functions.     

Effects of ammonia exposure on stress and immune response in juvenile turbot (Scophthalmus maximus)

The aim of this study was to investigate the effects of ammonia exposure on stress and immune response in turbot. The species was exposed to five total ammonia nitrogen (TAN) concentrations: 0 (control), 1, 5, 20 and 40 mg L^?1 for 96 h. After 0, 24, 48 and 96 h of exposure, blood samples were collected to measure the levels of corticotropin‐releasing hormone (CRH), adrenocorticotropic hormone (ACTH), cortisol, growth hormone (GH), lysozyme (LZM), complement 3 (C3), complement 4 (C4) and immunoglobulinM (IgM); liver samples were taken to analyse oxidative stress parameters (superoxide dismutase, SOD; catalase, CAT; glutathione, GSH; malondialdehyde, MDA), and gene expression of heat shock proteins (HSP 70 and HSP 90) and insulin‐like growth factor‐1 (IGF‐1). The results showed that exposure to higher concentrations of TAN (20 and/or 40 mg L^?1) enhanced the levels of CRH, ACTH and cortisol and attenuated the levels of GH, LZM, C3, C4 and IgM in plasma of turbot after 48 and 96 h. In liver, TAN (20 and/or 40 mg L^?1) apparently increased the activities of antioxidative enzymes (SOD and CAT), mRNA levels of HSP (HSP 70 and 90) and formation of MDA, decreased the content of GSH and mRNA levels of IGF‐1 after 48 and 96 h of exposure. Overall, our results suggested that high ammonia exposure caused activation of hypothalamic–pituitary–interrenal axis, inhibition of GH/IGF axis and immunity, and occurrence of oxidative stress.     

Cortisol and Behavioral Response to Handling (Acute) and Confinement (Chronic) Stressors in Juvenile Spotted Wolffish,Anarhichas minor

The purpose of this study was to determine the cortisol response of spotted wolffish (Anarhichas minor) after exposure to air immersion and netting (acute stress) under a range of increasing densities (chronic stressor). In addition, the presence of a cumulative negative impact from chronic stress was assessed by the application of an additional acute stressor following rearing at various densities, and proxies of behavior were evaluated (feeding and aggression data). The stress response to air immersion and netting led to increasing plasma cortisol values at 0.5, 13, and 37 h post-stress, with the highest value achieved after 13 h. At 168 h, cortisol concentrations returned to similar pre-stress value. Changes in cortisol concentrations were relatively low after acute stress (five to six fold increases) and recovery time long lasting (>37 h). Prolonged rearing at 20, 30, and 40 kg m^?2 showed a non-significant trend of increasing cortisol values with increasing density, and the cortisol response after the application of an additional acute stressor was significantly altered, i.e., higher cortisol levels were measured in unstressed (chronic stress only) compared to stressed fish (chronic stress + acute stress). Our results suggest that (1) spotted wolffish is a low responder that additionally displays a long-lasting cortisol elevation following an acute stressor; (2) fixed densities did not lead to significant differences of plasma cortisol concentration or aggression levels, although involved marked changes in daily feed intake and food conversion efficiency were observed; and (3) cortisol levels reached acute stress values after prolonged chronic stress. Although this species displays indications of being relatively resistant to handling disturbances during aquaculture practices, it is nevertheless responsive to chronic stress factors that could alter the physiological response to subsequent acute stressor.     

Effects of melatonin and green-wavelength LED light on the physiological stress and immunity of goldfish, <Emphasis Type="Italic">Carassius auratus</Emphasis>, exposed to high water temperature

This study investigated the effects of increasing water temperature (22–30 °C) on the physiological stress response and immunity of goldfish, Carassius auratus, and the ability of green light-emitting diode (LED) irradiation or melatonin injections to mitigate this temperature-induced stress. To evaluate the effects of either green-wavelength LED light or melatonin on stress in goldfish, we measured plasma triiodothyronine (T₃), thyroxine (T₄), and thyroid hormone receptor (TR) mRNA expression; plasma cortisol and glucose; and immunoglobulin M (IgM) and lysozyme mRNA expression. The thyroid hormone activities, TR mRNA expression, and plasma cortisol and glucose were higher in goldfish exposed to high-temperature water, but were lower after exposure to melatonin or green-wavelength LED light. Lysozyme mRNA expression and plasma IgM activity and protein expression were lower after exposure to high water temperatures and higher after melatonin or green-wavelength LED light treatments. Therefore, high water temperature induced stress and decreased immunity; however, green-wavelength LED light and melatonin treatments mitigated the effects of stress and enhanced immunity. The benefits of melatonin decreased with time, whereas those of green-wavelength LED treatment did not.