GFAP expression in the optic nerve and increased Н2S generation in the integration centers of the rainbow trout（Oncorhynchus mykiss） brain after unilateral eye injury

Hydrogen sulfide(H2S)is considered as a protective factor against cardiovascular disorders.However,there are few reports on the effects of H2S in the central nervous system during stress or injury.Previous studies on goldfish have shown that astrocytic response occurs in the damaged and contralateral optic nerves.Glial fibrillary acidic protein(GFAP)concentration in the optic nerves of rainbow trout has not been measured previously.This study further characterized the astrocytic response in the optic nerve and the brain of a rainbow trout(Oncorhynchus mykiss)after unilateral eye injury and estimated the amount of H2S-producing enzyme cystathionineβ-synthase(CBS)in the brain of the rainbow trout.Within 1 week after unilateral eye injury,a protein band corresponding to a molecular weight of 50 kDa was identified in the ipsi-and contralateral optic nerves of the rainbow trout.The concentration of GFAP in the injured optic nerve increased compared to the protein concentration on the contralateral side.The results of a quantitative analysis of GFAP+cell distribution in the contralateral optic nerve showed the largest number of GFAP+cells and fibers in the optic nerve head.In the damaged optic nerve,patterns of GFAP+cell migration and large GFAP+bipolar activated astrocytes were detected at 1 week after unilateral eye injury.The study of H2S-producing system after unilateral eye injury in the rainbow trout was conducted using enzyme-linked immunosorbent assay,western blot analysis,and immunohistochemistry of polyclonal antibodies again st CBS in the integrative centers of the brain:telencephalon,optic tectum,and cerebellum.Enzyme-linked immunosorbent assay results showed a 1.7-fold increase in CBS expression in the rainbow trout brain at 1 week after unilateral eye injury compared with that in intact animals.In the ventricular and subventricular regions of the rainbow trout telencephalon,CBS+radial glia and neuroepithelial cells were identified.After unilateral eye injury,the number of CBS+neuroepithelial cells in the pallial and subpallial periventricular regions of the telencephalon increased.In the optic tectum,unilateral eye injury led to an increase in CBS expression in radial glial cells;simultaneously,the number of CBS+neuroepithelial cells decreased in intact animals.In the cerebellum of the rainbow trout,neuroglial interrelationships were revealed,where H2S was released,apparently,from astrocyte-like cells.The organization of H2S-producing cell complexes suggests that,the amount of glutamate produced in the rainbow trout cerebellum and its reuptake was controlled by astrocyte-like cells,reducing its excitotoxicity.In the dorsal matrix zone and granular eminences of the rainbow trout cerebellum,CBS was expressed in neuroepithelial cells.After unilateral eye injury,the level of CBS activity increased in all parts of the cerebellum.An increase in the number of H2S-producing cells was a response to oxidative stress after unilateral eye injury,and the overproduction of H2S in the cerebellum occurred to neutralize reactive oxygen species,providing the cells of the rainbow trout cerebellum with a protective effect.A structural reorganization in the dorsal matrix zone,associated with the appearance of an additional CBS+apical zone,and a decrease in the enzyme activity in the dorsal matrix zone,was revealed in the zones of constitutive neurogenesis.All experiments were approved by the Commission on Biomedical Ethics,A.V.Zhirmunsky National Scientific Center of Marine Biology(NSCMB),Far Eastern Branch,Russian Academy of Science(FEB RAS)(approval No.1)on July 31,2019.

Screening of Saprolegniasis Preventive Drugs for Golden Trout (Oncorhynchus mykiss) Fertilized Eggs During Hatching

In order to screen the effective preventive drugs for saprolegniasis occurred during hatching of the fertilized eggs of golden trout, effects of two kinds of self-made Chinese herbal compounds（AB） and two kinds of chemical bactericides（peroxyacetic acid andhydrogen peroxide, CD） with three disinfection concentrations were compared in this study. The fertilized eggs of golden trout were randomly divided into 13 groups, each group with two parallels of 1 000 eggs. Drugs at high,medium and low concentration were respectively used to immerse the fertilized eggs35 min for disinfection once a day. The numbers of live and dead eggs were recorded each day before disinfection and the numbers of survival eyed eggs were counted in each experimental group after finishing the whole test. The results indicated that all of four kinds of drugs used here had a certain effect on prevention and control of saprolegniasis during hatching of fertilized eggs of golden trout, and also showed a correlation between the concentrations and effects. After the selection of several drugs, we found that group B-medium, C-medium and D-high exhibited the most remarkable effects on control of saprolegniasis. However, careful consideration should be given to chemical drugs residues and their potential hazard to the eyed eggs. Therefore, Chinese herbal compound B was suggested to be used for prevention and control of saprolegniasis to achieve the healthy aquaculture. And the concentration and operation time of Chinese herbal compound B should be strictly controlled when used in disinfection of fertilized eggs.

IMMUNE FUNCTION OF IMMATURE RAINBOW TROUT ( Oncorhynchus mykiss ) RELATED WITH PHOTOPERIOD

Radioimmunoassay,enzyme linked immunospot assay and enzyme immunoassay were used for the determinations of plasma steroid hormone's level,antibody producing cell's counting and IgM level in this study.The decreased number of antibody producing cells and low IgM levels were observed in sexual immature rainbow trout during the spawning season.These fish were reared under almost constant water temperature and natural photoperiod.Moreover,low IgM level was also observed in immature rainbow trout,which were reared under short photoperiod,and IgM level was not changed by treatment of testosterone.The results suggest that photoperoid may cause the changes in immune competence.It is possible that circadian rhythm accompanied with photoperiod may influence physiological function of fish,so that immune competence is changed.

高温胁迫对虹鳟(Oncorhynchus mykiss)肝脏中抗氧化酶活性和免疫相关基因表达的影响

夏季高温对虹鳟(Oncorhynchusmykiss)网箱养殖会产生极大威胁,高温胁迫会造成虹鳟应激甚至死亡。为探究高温胁迫对虹鳟肝脏抗氧化响应及相关免疫基因的影响,选取虹鳟“水科一号”幼鱼[(24.8±10.0)g]为实验对象,通过连续升温达到高温胁迫条件,筛选出高温敏感组和耐受组,并对它们的抗氧化酶活性、免疫相关基因表达和随机扩增多态性DNA(RAPD)片段化进行比较研究。结果表明:敏感组与耐受组的超氧化物歧化酶(SOD)和过氧化氢酶(CAT)活性含量不存在显著性差异(P>0.05),但均显著高于对照组(P<0.05);敏感组的缺氧诱导因子-1α(hif-1α)、白细胞介素-1β(il-1β)以及热休克蛋白10 (hsp10)基因的相对表达量较耐受组的分别高1.8倍、1.28倍和16.5倍(P<0.05);耐受组的热休克蛋白70 (hsp70)基因的表达比敏感个体高1.37倍(P<0.05);RAPD图谱反映出敏感组的DNA损伤比耐受组更严重。高温胁迫对虹鳟幼鱼hif-1α、hsp70和hsp10基因产生强烈的应答性表达上调,且RAPD针对高温耐受个体可有效进行识别。

17α,20β-DIHYDROXY-4-PREGNENE-3-ONE SUPPRESSES PLASMA IgM LEVELS IN RAINBOW TROUT (Oncorhynchus mykiss)

The relationships between 17α,20β dihydroxy 4 pregnene 3 one (17α,20β DP) and plasma IgM and total protein levels were investigated in rainbow trout, Oncorhynchus mykiss .IgM and total protein levels decreased in both sexes of mature rainbow trout when 17α,20β DP levels increased during the spawning season,while the elevated 17α,20β DP suppressed IgM levels and reversibly enhanced total protein concentrations in immature trout.This represents the first report of the effect of 17α,20β DP on fish immunity.These data suggest that the increase of 17α,20β DP in spawning season may be related to infectious skin diseases.

温度和盐度对虹鳟(Oncorhynchus mykiss)“水科1号”生长、消化酶活性和相关基因表达的影响

温度和盐度变化的影响是虹鳟(Oncorhynchus mykiss)海水驯化和养殖生产中需要解决的重要问题。为探究温度和盐度对虹鳟生长发育的影响,通过在3种温度(10、16和22℃)条件下均设置5种盐度梯度处理(盐度分别为0、8、16、24、32),分别以A_(1)~A_(5)表示10℃各盐度组,以B_(1)~B_(5)表示16℃各盐度组,以C_(1)~C_(5)表示22℃各盐度组,将温度16℃且盐度为0组(B_(1))作为淡水对照组,开展为期21 d的养殖实验。养殖实验结束后分析不同温度和盐度对虹鳟生长、肠道消化酶活性、鳃和肠组织中生长相关基因(gh和igf-1)、应激相关基因(hsp70)和渗透压调节相关基因(aqp3和nka)表达的影响。结果显示,除B_(2)(16℃下盐度为8)盐度组的饵料转化率(FCE)、增重率(WGR)和特定生长率(SGR)较B_(1)(淡水对照组)显著升高,肠道中淀粉酶和脂肪酶活性分别较B1(淡水对照组)显著升高约23%和8%外(P<0.05),其余实验组以上指标均较淡水对照组降低。此外,鳃和肠组织中,B_(2)和B_(3)组gh和igf-1的表达量较对照组显著上调(P<0.05),而其余实验组gh和igf-1的表达量较对照组均显著下调(P<0.05)。鳃组织中B_(2)和B_(3)组以及肠组织中B_(2)组的hsp70表达量较对照组无显著差异(P>0.05),其余实验组hsp70的表达量较对照组显著上调(P<0.05)。不同温度条件下,鳃组织中aqp3表达量随实验组盐度增大呈下调趋势,而肠组织中则呈上调趋势;两组织中nka表达量随实验组盐度增大均呈上调趋势。研究结果表明,16℃下8盐度组的虹鳟较淡水组生长更好。因此,在虹鳟适宜的温度下,适当地提升养殖水体的盐度有利于促进虹鳟的生长发育,这为完善海水条件下虹鳟的驯化和养殖提供了基础资料。

Virtual screening,molecular docking and identification of umami peptides derived from Oncorhynchus mykiss

Oncorhynchus mykiss is delicious and contains abundant flavor substances.However,few studies focused on umami peptides of O.mykiss.In the current work,umami peptides derived from O.mykiss were identified using virtual screening,molecular docking,and electronic tongue analysis.First,the O.mykiss protein was hydrolyzed using the PeptideCutter online enzymolysis program.Subsequently,water-soluble and toxicity screening were performed by Innovagen and ToxinPred software,respectively.The potential peptides were docked with umami receptor T1R1/T1R3.Furthermore,taste properties of potential peptides were validated by electronic tongue.Docking results suggested that the three tetrapeptide EANK,EEAK,and EMQK could enter the binding pocket in the T1R1 cavity,wherein Arg151,Asp147,Gln52,and Arg277 may play key roles in the production of umami taste.Electronic tongue results showed that the umami value of EANK,EEAK,and EMQK were stronger than monosodium glutamate.This work provides a new insight for the screening of umami peptides in O.mykiss.

Neurolin expression in the optic nerve and immunoreactivity of Pax6-positive niches in the brain of rainbow trout(Oncorhynchus mykiss) after unilateral eye injury

In contrast to astrocytes in mammals, fish astrocytes promote axon regeneration after brain injury and actively participate in the regeneration process. Neurolin, a regeneration-associated, Zn8-1abeled protein, is involved in the repair of damaged optic nerve in goldfish. At 1 week after unilateral eye injury, the ex- pression of neurolin in the optic nerve and chiasm, and the expression of Pax6 that influences nervous system development in various brain regions in the rainbow trout （Oncorhynchus mykiss） were detected. Immunohistochemical staining revealed that the number of Zn8~ cells in the optic nerve head and intraor- bital segment was obviously increased, and the increase in Zn8~ cells was also observed in the proximal and distal parts of injured optic nerve. This suggests that Zn8＊ astrocytes participate in optic nerve regeneration. ELISA results revealed that Pax6 protein increased obviously at 1 week post-injury. Immunohistochemi- cal staining revealed the appearance of Pax6＋ neurogenic niches and a larger number of neural precursor cells, which are mainly from Pax6＋ radial glia cells, in the nuclei of the diencephalon and optic tectum of rainbow trout （Oncorhynchus mykiss）. Taken together, unilateral eye injury can cause optic nerve reaction, and the formation of neurogenic niches is likely a compensation phenomenon during the repair process of optic nerve injury in rainbow trout （Oncorhynchus mykiss）.

Immune response,stress resistance and bacterial challenge in juvenile rainbow trouts Oncorhynchus mykiss fed diets containing chitosan-oligosaccharides

Effects of dietary supplementation of chitosan-oligosaccharides （COS） on the growth performance, immune response, stress resistance, and disease resistance of juvenile rainbow trout Oncorhynchus mykiss were studied. Four experimental diets containing 0, 20, 40, or 60 mg/kg COS （COSO, COS20, COS40, and COS60, respectively） were fed to juvenile rainbow trout （initial weight = 5.2 ± 0.3 g） for 8 weeks. By the end of the feeding trial, representative groups of fish from each dietary treatment were challenged with stressor （30 see air exposure） and pathogen exposure （intraperitoneal injection with Aeromonas hydrophila ）. Results showed that supplementation of COS in diets did not affect production performance and body composition of rainbow trout. However, fish fed the COS40 diet demonstrated improved phagocytic activities, respiratory burst activities and decreased serum cortisol level. Additionally, survival following A. hydrophila challenge was significant higher among fish fed the COS-supplemented feeds, although there was no difference based on the level of supplementation. The present study suggests that COS can be used as an immuno-stimulant in rainbow trout feeds

Temperature-Dependent Fatty Acid Composition Change of Phospholipid in Steelhead Trout (Oncorhynchus mykiss) Tissues

In this study, the changes of the fatty acid composition of phospholipid in different tissues(muscle, heart, brain and spleen) of steelhead trout(Oncorhynchus mykiss) were analyzed when the water temperature decreased gradually from 16 to 12℃℃, 8℃, 6℃, 4℃, 2 and 1℃℃. Three fish individuals each tank(average weight 70.32 g ± 9.12 g) were collected and used to analysis at each designed temperatures. At normal temperature(16℃), the fatty acid composition of phospholipid of muscle and heart was similar each other. The highest concentration of saturate fatty acids(SFA) was found in the phospholipid of spleen. The brain phospholipid contained higher oleic acid(18:1 n9) than the phospholipid of other tissues at 16℃. When the environmental temperature decreased, the concentration of unsaturated fatty acids of phospholipids in all tissues increased, and accordingly the ratio pf the unsaturated to saturated fatty acids(U/S) and unsaturation index(UI) increased, indicating that steelhead trout can compensate temperature-dependent changes in membrane fluidity by remodeling the fatty acid composition of phospholipids. The changes in the fatty acid composition of phospholipid were tissue-specific. At the early stages of the experiment(16 to 8℃℃), the fatty acid composition of phospholipid changed remarkably in muscle, heart, and spleen. When temperature decreased to less than 8℃, an obvious response of phospholipid fatty acid was observed in all tissues. The change of phospholipid composition of steelhead trout tissues may be affected by both cold stress and starvation when the temperature decreased to 2℃, and the change of phospholipid composition of muscle was very obvious.

Comparisons of Salinity Adaptation in Terms of Growth, Body Composition, and Energy Budget in Juveniles of Rainbow and Steelhead Trouts (Oncorhynchus mykiss)

This study examined the effect of different salinities(0, 5, 10, 15, 20, 25 and 30) on the growth performance and energy budget of juveniles of two different ecotypes of Oncorhynchus mykiss, landlocked rainbow trout and anadromous steelhead trout. In the 42 d experiment, fish were cultured in three replicate tanks per salinity treatment(eight fish per tank). At the end of the experiment, the growth of rainbow and steelhead trouts was significantly higher at salinities of 5 and 10, respectively, than at all other salinities. The protein, lipid and energy content of both ecotypes declined with the increase of salinity. Based on their energy budgets, the percentage of energy consumed for growth by rainbow and steelhead trouts were significantly higher at salinities of 5(34.00% ±1.69%) and 10(43.76% ± 1.29%), respectively, than at all other salinities. The percentage of energy consumed for respiration by rainbow and steelhead trouts was lower at salinities of 5(54.90% ± 1.77%) and 10(46.73% ± 0.62%), respectively, than at all other salinities. Our results indicated that the salinity adaptation ability of juvenile steelhead trout was slightly better than that of juvenile rainbow trout, and salinities of 10 and 5, respectively, were most suitable for growth of these two fishes.

An Effective Method of Prompting Juvenile Rainbow Trout (Oncorhynchus mykiss) to Cope with Heat Stress

In the present study,juvenile rainbow trout(Oncorhynchus mykiss)were acclimated at 5 temperatures.Fish in the control group(C0)were reared at a constant temperature(16℃);trout in four other treatments(A0,A3,A6,and A9)were acclimated to a high temperature(22℃)for 0,3,6,and 9 d,respectively,and then returned to normal temperature(16℃)for 7d.The temperature was then raised to 20℃and the fish were cultured for 40 d.The results showed that the growth rates of A3,A6,and A9 were higher than that of A0 but lower than that of C0.The growth rate of A9 was the highest among the 4 acclimation groups.The activities of serum transaminase and liver antioxidant enzyme significantly increased during acclimation.At the beginning of growth,the activities of enzymes were lower in A3,A6,and A9 with the lowest in A9.In addition,the transcript abundance of heat shock protein(HSP)60 gene in A9 was not significantly different from that of C0 during growth.HSP70 in A9 significantly increased at the beginning and returned to that of C0 at the end.Our findings indicated that pre-acclimation improved the high temperature tolerance with the best effectiveness observed at 22℃for 9 d.A possible mechanism underlining such phenomenon is the improvement of antioxidant defense system.

Influence of Maternal and Larval Immunisation against <i>Lactococcus garviae</i>Infection in Rainbow Trout <i>Oncorhynchus mykiss</i>(Walaum) Lysozyme Activity and IgM Level

This study evaluated efficacy of maternal and larval immunisation against Lactococcus garviae infection and on the lysozyme and immunoglobulin (IgM) levels in rainbow trout Oncorhynchus mykiss (Walaum). Forty-eight-day-old larvae (mean weight 96 mg) originating from injected weekly with letrozole and immunised, only immunised and non-immunised parents were experimentally infected with the L. garvieae, and the mortality rate was recorded daily. Larvae were vaccinated by immersion at 58 days post hatch with live L. garvieae (109 cells/mL) for 15 min. Every third day post larvae vaccination, two larvae from each group were collected for analysis lysozyme (by a method based on the ability of lysozyme to lyse the bacterium Micrococcus lysodeikticus) and IgM (by enzyme-linked immunosorbent assay (ELISA)) parameters. Vaccinated and control larvae were tested for protection against L. garvieae 30 days post larvae immunization when the larvae were 88 days old. Larvae were challenged by bath exposure with live L. garvieae (109 cells/mL) for 2 min and monitored for mortality for at least 10 days following challenge. The challenge experiment with L. garvieae showed a significant reduction in larvae from immunised (54.44% ± 0.64%) and injected weekly with letrozole and immunised fish (52.96% ± 0.97%) compared to larvae from control fish (62.96% ± 2.22%). Vaccinated larvae originated from injected weekly with letrozole and immunised parents showed significantly higher lysozyme activity compared to other fish groups. Vaccinated larvae showed significantly less mortality compared to controls. The relative percent survival (RPS) values of larvae from only immunised, injected weekly with letrozole and immunised and non-immunised parents vaccinated with L. garvieae were 67.36% ± 0.9%, 68.05% ± 0.66% and 48.27% ± 2.79% respectively. The results indicate that the effect of maternal immunization rainbow trout against L. garvieae infection by eliciting the immune responses as indicated by an increase in the IgM level and lysozyme activity.

Effect of Stocking Density on Water Quality and(Growth, Body Composition and Plasma Cortisol Content) Performance of Pen-Reared Rainbow Trout(Oncorhynchus mykiss)

The goal of the study was to examine the effect of stocking density on the water quality of culture area, as well as the growth, body composition and cortisol content of rainbow trout(Oncorhynchus mykiss). Pen-reared trout were stocked in densities of 40, 60, 80 fish individuals m^(-3)(4.6, 6.6, 8.6 kg m^(-3), SD1, SD2 and SD3 groups, respectively) for 300 days. Compared to the water from SD1 and SD2, that from SD3 exhibited significantly higher NH_4^+-N content and COD(chemical-oxygen-demand), and a significant reduction of dissolved oxygen in day 180(40.6 kg m^(-3)). Stocking density was significantly associated with body weight, standard length, VSI(viscerosomatic index), CF(condition factor) and FC(food coefficient) in group SD3, particularly in day 240 and day 300(45 or 49.3 kg m^(-3)). Increased crude fat and decreased crude protein were displayed in high density group when the density reached to 36 kg m^(-3). As a cumulative effect of density-related stress, VSI, CF, FC, moisture, and crude protein content varied over time in each density group(SD1, SD2, and SD3). In summary, trout exhibited a better growth performance in low density(26.3 kg m^(-3)) than those reared in high densities(36 and 45 kg m^(-3)). The results indicate that rainbow trout(114.44 g ± 6.21 g, 19.69 cm ± 0.31 cm) initially stocked in 6.6 or 8.6 kg m^(-3) should be lightened to less than 36 kg m^(-3) after an intensive rearing for 240 days.

Effect of micro-algae Schizochytrium sp.supplementation in plant diet on reproduction of female rainbow trout(Oncorhynchus mykiss):maternal programming impact of progeny

Background:The broodstock diet,and in particular the lipid and fatty acid composition of the diet,is known to play a key role in reproductive efficiency and survival of the progeny in fish.A major problem when replacing both fish meal and fish oil by plant sources is the lack of n-3 long chain polyunsaturated fatty acids,such as eicosapentaenoic acid(EPA)and docosahexaenoic acid(DHA).To address this problem,we studied the effect of the plant-based diet supplemented with Schizochytrium sp.microalgae,source of DHA,compared to a conventional commercial diet rich in fish meal and fish oil on reproductive performance and egg quality and the consequences on progeny,in female rainbow trout broodstock.Results:The results demonstrated that DHA-rich microalgae supplementation in a plant-based diet allowed for the maintenance of reproductive performance and egg quality comparable to a conventional commercial feed rich in fish meal and fish oil and led to an increased significant fry survival after resorption.Moreover,when females were fed a plant-based diet supplemented with micro-algae,the 4-month-old progenies showed a significant higher growth when they were challenged with a similar diet as broodstock during 1 month.We provide evidence for metabolic programming in which the maternal dietary induced significant protracted effects on lipid metabolism of progeny.Conclusions:The present study demonstrates that supplementation of a plant-based diet with DHA-rich microalgae can be an effective alternative to fish meal and fish oil in rainbow trout broodstock aquafeed.

ANNUAL CHANGES IN PLASMA LEVELS OF CORTISOL AND SEX STEROID HORMONES IN MALE RAINBOW TROUT, ONCORHYNCHUS MYKISS

The profiles of cortisol, testosterone, 11 ketotestosterone and 17α, 20β dihydroxy 4 pregnene 3 one in male rainbow trout reared under constant water temperature and natural photoperiod were determined by radioimmunoassay. Gonads of male rainbow trout reached maturity when the fish were two years old. Changes in the plasma levels of both sex steroid hormones and cortisol were closely related to the GSI. Plasma levels of testosterone, 11 ketotestosterone and 17α, 20β dihydroxy 4 pregnene 3 one showed a clear peak in the annual breeding season, when the GSI reached their maxima. Plasma cortisol levels also showed clearly seasonal changes in both two and three year old fish. The results suggest that the elevated plasma levels of cortisol may not just be due to stresses during the breeding season but have certain physiological functions in the reproduction of rainbow trout.

Exploring the effects of dietary inulin in rainbow trout fed a high‑starch,100%plant‑based diet

Background High dietary carbohydrates can spare protein in rainbow trout(Oncorhynchus mykiss)but may affect growth and health.Inulin,a prebiotic,could have nutritional and metabolic effects,along with anti-inflammatory properties in teleosts,improving growth and welfare.We tested this hypothesis in rainbow trout by feeding them a 100%plant-based diet,which is a viable alternative to fishmeal and fish oil in aquaculture feeds.In a two-factor design,we examined the impact of inulin(2%)as well as the variation in the carbohydrates(CHO)/plant protein ratio on rainbow trout.We assessed the influence of these factors on zootechnical parameters,plasma metabolites,gut microbiota,production of short-chain fatty acids and lactic acid,as well as the expression of free-fatty acid receptor genes in the mid-intestine,intermediary liver metabolism,and immune markers in a 12-week feeding trial.Results The use of 2%inulin did not significantly change the fish intestinal microbiota,but interestingly,the high CHO/protein ratio group showed a change in intestinal microbiota and in particular the beta diversity,with 21 bacterial genera affected,including Ralstonia,Bacillus,and 11 lactic-acid producing bacteria.There were higher levels of butyric,and valeric acid in groups fed with high CHO/protein diet but not with inulin.The high CHO/protein group showed a decrease in the expression of pro-inflammatory cytokines(il1b,il8,and tnfa)in liver and a lower expression of the genes coding for tight-junction proteins in mid-intestine(tjp1a and tjp3).However,the 2%inulin did not modify the expression of plasma immune markers.Finally,inulin induced a negative effect on rainbow trout growth performance irrespective of the dietary carbohydrates.Conclusions With a 100%plant-based diet,inclusion of high levels of carbohydrates could be a promising way for fish nutrition in aquaculture through a protein sparing effect whereas the supplementation of 2%inulin does not appear to improve the use of CHO when combined with a 100%plant-based diet.

The Effects of Letrozole in Transfer of Maternal Immunity against Lactococcosis to Eggs and Larvae in Rainbow Trout (<i>Oncorhynchus mykiss</i>, Walbaum)

This study evaluated transfer of maternal lysozyme and immunoglobulin (IgM) against Lactococcus garviea, the causative agent of lactococcosis to eggs and larvae in rainbow trout. Changes in circulating lysozyme and IgM during development of eggs and larvae were measured by a method based on the ability of lysozyme to lyse the bacterium Micrococcus lysodeikticus and enzyme-linked immunosorbent assay (ELISA) respectively. For doing this, twelve broodstocks were injected weekly with 2.5 mg&middotkg-1 letrozole (an endocrine disrupter component) two months before spawning season and vaccinated intraperitoneally (i.p) with a bacterin (inactivated L. garviae) one month before spawning. Twelve broodstocks for vaccination and twelve female rainbow trouts as control group were also immiunised (i.p) with the bacterin and injected (i.p) with PBS respectively. Results showed that at day 8 after hatching, lysozyme and IgM levels during pre-larval stages decreased gradually, as yolks were absorbed. Lysozyme and IgM levels were significantly higher in the letrozole injected immiunised parents 30 days after immunisation as well as their larvae compared to the control group (p L. garviae) (one month before spawning) in maternal transfer of lysozyme and IgM levels to eggs and larvae.

Rainbow Trout (<i>Oncorhynchus mykiss</i>) Cage Culture: Preliminary Observations of Surface Sediment’s Chemical Parameters and Phosphorus Release in Gokcekaya Reservoir, Turkey

This research was conducted in Gokcekaya Reservoir, which is located on the Sakarya River (Ankara, Turkey). Sediment samples were obtained before and after culture periods at a rainbow trout (Oncorhynchus mykiss) farm with a capacity of 950 t·y-1. Total phosphorus (TP: 8.80 ± 0.50 and 9.10% ± 0.20%), total nitrogen (TN: 17.0 ± 0.20 and 17.05% ± 0.10%), organic matter (OM: 14.40 ± 0.40 and 14.60% ± 0.20%), redox potential (327.00 ± 0.08 and 170.00 ± 4.08 mV), water content (97.68 ± 0.28 and 96.38% ± 0.41%) and total organic carbon (TOC: 11.30 ± 0.10 and 13.40% ± 0.10%) were measured before and after the culture period, respectively. The mean rank order of sediment heavy metal was evaluated as Fe > Mn > Ni > Zn > Cr > Cu. The soluble reactive phosphorus (SRP) concentrations in the sediment pore water were 2.52 ± 0.14 and 7.75 ± 1.18 μg·L-1;ammonium (NH3) was measured as 1.13 ± 0.09 and 1.18 ± 0.06 μg·L-1;nitrite (NO2) was 8.83 ± 0.23, 12.75 ± 0.22 μg·L-1;nitrate (NO3) was elevated at 0.14 ± 0.07 and 0.24 ± 0.02 μg·L-1, and positive phosphorus release remained at low levels: 3.35 μg&#183m-2d-1 (before the culture period, September 2011) and 11.04 μg·m-2d-1 (after the culture period, April 2012). The data on the sediment and the sediment pore water of the rainbow trout culture in Gokcekaya Reservoir shows that the cage culture in its present condition has no negative effect on sediment quality.

Effects of irradiated Ergosan on the growth performance and mucus biological components of rainbow trout Oncorhynchus mykiss

Effects of irradiated and non-irradiated Ergosan extract(alginic acid) on rainbow trout growth performance and skin mucosal immunity were compared. Ergosan was irradiated at 30 kGy in a cobalt-60 irradiator. A total of 252 fish(128.03±9.4 g) were randomly divided into four equal groups,given the basal diet either unsupplemented with Ergosan(control group) or supplemented with crude Ergosan(5 g/kg),ethanol-extracted Ergosan(0.33 g/kg) or irradiated Ergosan(0.33 g/kg) according to this protocol: basal diet for 15 days,treatment diet for 15 days,basal diet for 10 days and treatment diet for 15 days. Highest growth performance was observed in fish fed irradiated Ergosan(P<0.05). Dietary administration of different Ergosan types did not cause any changes in mucus protein level,but improved alkaline phosphatase level and hemagglutination titer compared with the control(basal diet without Ergosan) on day 55 offeeding trial(P<0.05). Furthermore,the highest value of lysozyme activity was observed in gamma-irradiated Ergosan on day 55. In conclusion,gamma-irradiated Ergosan at 0.33 g/kg was found to improve growth performance and mucus biological components significantly in comparison with the control group(basal diet without Ergosan).