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.

二倍体与三倍体虹鳟(Oncorhynchus mykiss)红细胞及部分血液指标的比较

对三倍体和二倍体虹鳟(Oncorhynchus mykiss)的红细胞大小(长、短径值和体积)、形态及部分血液指标(红细胞数、血红蛋白、红细胞压积、红细胞脆性和白细胞数)进行了比较。结果表明:三倍体虹鳟红细胞体积与二倍体比值为1.51∶1,细胞核大小与二倍体比值为1.49∶1,与理论值(1.5∶1)比较均无显著差异(P>0.05)。二倍体红细胞短径/长径比值为0.63,呈现出椭圆形;三倍体红细胞短径/长径比值为0.60,呈现出明显的长椭圆形,并有19%的红细胞有哑铃形或分裂的细胞核,这可作为区别二倍体鱼类的一个重要鉴定标志。三倍体虹鳟的红细胞数、红细胞压积和红细胞脆性明显小于二倍体(P<0.05),而血红蛋白与白细胞数与二倍体比较无明显差异(P>0.05)。

三倍体虹鳟(Oncorhynchus mykiss)血细胞发生的形态学研究

观察和测定了三倍体虹鳟(Oncorhynchus mykiss)肝脏、脾脏、头肾和外周血液血细胞的发生过程。结果显示:三倍体虹鳟外周血红细胞具有分裂的能力,外周血液是其进一步发育成熟的场所,其进一步发育成熟有核质非同步分裂(核分裂先于质分裂呈双核型)和核质哑铃型同步分裂两种形式。外周血液中未成熟红细胞、单核细胞、淋巴细胞和粒细胞细胞比例分别为5.81%、4.14%、4.52%和3.38%,其4类未成熟细胞比例明显高于造血器官;外周血液中成熟红细胞为69.6%,与造血器官成熟红细胞的比例无显著差异;外周血中单核细胞、淋巴细胞和粒细胞细胞比例分别为6.60%、4.71%和1.24%,三类细胞比例明显低于造血器官(头肾中单核细胞除外)。

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.

菜粕替代鱼粉对虹鳟(Oncorhynchus mykiss)生长、体组成和血液学指标的影响

研究旨在探讨菜粕替代鱼粉对虹鳟（Oncorhynchus mykiss）生长、体组成和血液学指标的影响。以初始体重（9．80±0．04）g的虹鳟为试验对象，用菜粕替代饲料中0（RSR0，对照组1、10％（RSR10）、20％（RSR20）、30％（RSR30）、50％（RSR50）和70％（RSR70）的鱼粉蛋白，配制成6种等氮、等能的饲料，进行为期90d的养殖试验。结果显示，随着菜粕替代比例的增加，虹鳟的增重率、特定生长率、蛋白质效率及饲料系数在对照组与RSR10-RSR30组之间无显著差异（P〉0．05）：RSR50和RSR70组的增重率、特定生长率、蛋白质效率显著低于其他各组（p〈0．os）。全鱼的粗蛋白、粗脂肪和粗灰分各组间无显著差异（P〉0．05）；RSR70组虹鳟肌肉的粗蛋白、粗脂肪和粗灰分含量均显著低于对照组（P〈0．05）。随着莱粕替代比例的增加，血清中总蛋白质、甘油三酯的含量，谷丙转氨酶以及谷草转氨酶的活性在RSR0-RSR30组间无显著差异（P〉0．05），RSR50和RSR70组的甘油三酯的含量及谷丙转氨酶和谷草转氨酶的活性显著高于对照组（P〈0．05）。试验结果表明，在本试验条件下，莱粕可替代饲料中30％的鱼粉，不会对虹鳟的生长、饲料利用、体组成及血液学指标产生显著影响。

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.

Genetic diversity and differentiation of masu salmon(Oncorhynchus masou masou) between and within cultured populations inferred from microsatellite DNA analysis

Masu salmon,Oncorhynchus masou masou,is one of the most valuable fishery species that has been introduced to China,though to date no studies on the genetic diversity and genetic relationship among hatchery populations has been performed with molecular markers.We undertook such a study and sampled 120 individuals from three hatchery stocks and analyzed 20 microsatellite loci.All loci were polymorphic and a total of 91 alleles were detected.A relatively low level of genetic diversity was revealed with effective number of allele of 3.1094,3.3299 and 3.1894 and expected heterozygosity of 0.6600,0.6648 and 0.6638 in the three stocks,respectively.Deviations from Hardy-Weinberg equilibrium were found due to heterozygote deficit.Accordingly,evidence of genetic bottlenecks were found in the three stocks.An individual assignment test demonstrated that 85% of individuals were correctly assigned into their original stocks.Pairwise Fst revealed that significant differentiation occurred between these three stocks.The results of the study indicated that disequilibrium of genetic structure and differentiation has occurred in all three stocks.This information collectively provides a basis for measures to avoid of loss of genetic diversity and introgression in Chinese aquaculture.

Rearing Velocity Impacts on Landlocked Fall Chinook Salmon (<i>Oncorhynchus tshawytscha</i>) Growth, Condition, and Survival

Juvenile landlocked Chinook salmon (Oncorhynchus tshawytscha) (mean ± SD initial weight 2.6 ± 0.7 g, fork length 6.3 ± 0.5) were reared in three different water velocities [0.5, 1.5 and 3.0 body length/s (BL/s)] for four weeks to determine possible effects of water velocity on growth, condition, and survival. Fish were sampled for weight, fork length, condition factor, hepatosomatic index (HSI), viscerosomatic index (VSI), and fin erosion after four weeks of feeding to satiation. At the end of the feeding trial, the fish were handled and transported to simulate stocking, with survival observed over the following 10 d. Following four weeks of feeding, fish reared in 0.5 and 1.5 BL/s had the same growth and food conversion ratio, but fish reared at 3.0 BL/s had a significant reduction in both metrics. Furthermore, fish reared at 1.5 BL/s had a significantly higher condition factor than fish reared in other treatments. No significant differences were found for HSI, VSI, fin erosion, or survival. The results from this study indicate that a moderate velocity (1.5 BL/s), which is necessary for circular tanks to be self-cleaning, is not detrimental to fish growth or condition, but a faster water velocity (3.0 BL/s) negatively affects fish growth and food utilization.

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.

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）.

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.

Compensatory growth response of rainbow trout Oncorhynchus mykiss Walbaum following short starvation periods

This sixty-day study was performed to determine the effects of short-term starvation and refeeding cycles on growth, feeding performances and body composition of rainbow trout （Oncorhynchus mykiss）. Three hundred trout fingerlings with an average initial weight of 17.54-0.06 g were randomly distributed in 15 circular fiberglass tanks. The fish were exposed to 5 different feeding regimes; control： continuously fed twice daily to apparent satiation; T1： starved for 1 day and re-fed for 2 days; T2： starved for 1 day and re-fed for 4 days; T3： starved for 3 days and re-fed for 12 days; T4： starved for 4 days and re-fed for 16 days. At the end of the experiment, growth performance, feed utilization, whole body ash and moisture contents were not significantly （P〉0.05） different among the treatments. However, whole body protein content in T3 was significantly higher than other treatments （P〈0.05）. A significant difference in whole body fat content was observed between T3 and the control group at the end of the experiment （P〈0.05）. In conclusion this experiment suggests that feeding schedules involving starvation （1-4 days） and re-feeding cycles are a promising feed management tool for rainbow trout culture.

Genetic diversity and differentiation of masu salmon(Oncorhynchus masou masou)between and within cultured populations inferred from microsatellite DNA analysis

Masu salmon,Oncorhynchus masou masou,is one of the most valuable fishery species that has been introduced to China,though to date no studies on the genetic diversity and genetic relationship among hatchery populations has been performed with molecular markers.We undertook such a study and sampled 120 individuals from three hatchery stocks and analyzed 20 microsatellite loci.All loci were polymorphic and a total of 91 alleles were detected.A relatively low level of genetic diversity was revealed with effective number of allele of 3.1094,3.3299 and 3.1894 and expected heterozygosity of 0.6600,0.6648 and 0.6638 in the three stocks,respectively.Deviations from Hardy-Weinberg equilibrium were found due to heterozygote deficit.Accordingly,evidence of genetic bottlenecks were found in the three stocks.An individual assignment test demonstrated that 85%of individuals were correctly assigned into their original stocks.Pairwise Fst revealed that significant differentiation occurred between these three stocks.The results of the study indicated that disequilibrium of genetic structure and differentiation has occurred in all three stocks.This information collectively provides a basis for measures to avoid of loss of genetic diversity and introgression in Chinese aquaculture.

Effects of Ferrous Fumarate on Growth Performance,Blood Biochemical Parameters and Trace Elements of Oncorhynchus mykiss

[ Objective] The study aimed to discuss the effects of ferrous fumarate on growth performance, blood biochemical parameters and content of trace element of Oncorhynchus mykiss. [ Method ] Juvenile rainbow trout with an initial weight of （89.2 ±0.2） g were fed with the basal fodder supplemented with different levels of ferrous fumarate （0, 20, 40, 80,160 and 480 mg/kg iron） for 60 d, and the six groups were named DO, D20, D40, D80, D160 and D480, wherein DO was as the control group, actually containing 62.60, 79.50, 99.60, 139.30, 215.20 and 538.40 mg/kg iron respectively. [ Result] The growth performance of juvenile rainbow trout was not affected by different dietary iron levels obviously （ P 〉 0.05）. With the increase of dietary iron level, hemoglobin （Hb） content and number of red blood cells（RBC） rose firstly and then leveled off. No significance was found in hematocrit （Hct） among the six groups （P 〉0.05）. Iron content in the whole body, vertebrae and muscle increased significantly with the improvement of dietary iron level（ P 〈0.05）, and iron concentration in the liver increased firstly and then leveled off in groups from D40 to D480. No significant difference in zinc content of the whole body was found among the six groups （ P〉0.05）, while zinc content in the vertebrae and muscle in control group was significantly higher than that of other groups （ P〈0.05）, and zinc concentration in the liver in groups DO and 1320 was significantly higher than that of other groups （ P 〈0.05）. Copper content in the whole body increased significantly with the increase of dietary iron level （P 〈 0.05 ）, while no significant difference was observed in the vertebrae （ P 〉0.05）, and copper concentration in the muscle in control group was significantly lower than that of other groups （ P 〈0.05）. Serum lysozyme （LZM） activity of group DO was significantly lower than that of other groups （ P 〈 0.05） except for group D480 （ P 〉 0.05）. Catalase （CAT） activity of serum enhanced significantly （ P 〈 0.05） from DO to EH0 and then decreased obviously （P 〈0.05）. [ Conclusion] Based on hemoglobin and iron content in the liver, the broken-line model analysis showed that the dietary iron level provided by ferrous fumarate for juvenile rainbow trout was estimated to be 99.8 and 100.4 mg/kg respectively in the experiment.

Comparative Analysis of Nutritional Components in Muscles between Wild and Cultured Masu Salmon Oncorhynchus masou

In this paper,approximate nutritional components and amino acid content were determined in muscles of female wild population(WP)with body weight of 2500-3000 g and female cultured population(CP)with body weight of 750-1250 g masu salmon Oncorhynchus masou in the gonadal development stage IV by conventional method.The results showed that there were significantly higher crude protein and significantly lower crude fat in fresh muscle of WP than that in CP(P<0.05),but not significant differences in the contents of moisture and crude ash between WP and CP(P>0.05).Eighteen kinds of amino acids were detected in muscles of WP and CP,with higher total content of amino acids(TAA),essential amino acids(EAA)and four kinds of delicious amino acids(DAA)in WP than those in CP(P<0.05).The amino acid score(AAS)and chemical score(CS)revealed that the first limiting amino acid was tryptophan in two populations,with essential amino acid index(EAAI)of 75.59%in WP and 70.77%in CP.The findings indicated that the amino acid contents in muscles of CP are lower than that of WP,but the amino acid nutritional value evaluation indicators of both populations are very close,and both have high nutritional value.

Combined Effects of Dietary Bacillus subtilis and Trans-cinnamic Acid on Growth Performance,Whole Body Compositions,Digestive Enzymes and Intestinal bacteria in Rainbow Trout(Oncorhynchus mykiss)

In this study,the combined effects of dietary Bacillus subtilis(BS,107 g/cfu)and different levels(0.025%,0.050%,0.075%and 0.150%)of trans-cinnamic acid(CA)on fish growth performance,whole body compositions,digestive enzymes,intestinal bacteria and internal organ index of rainbow trout(Oncorhynchus mykiss)were investigated.Six different experimental groups including control group(C),C+BS,0.025%CA+BS,0.050%CA+BS,0.075CA+BS,0.150%CA+BS)were established.According to the results obtained,growth performance,whole body compositions and digestive pH were not statistically significant among groups.Further,no significant differences were found between experimental groups in terms of the intestinal enzymes(trypsin,alkaline phosphatase and lipase)and gastric pepsin.Significantly higher levels of intestinal amylase were found in the control+BS,0.025%CA+BS,0.050%CA+BS,and 0.075%CA+BS compared to the control and 0.150%CA+BS groups.Moreover,coliform and Enterobacteriaceae counts were highest in the control+B.subtilis and lowest in the 0.150%CA+B.subtilis groups.

Effect of Tank Colure Effects on Survival and Growth of Oncorhynchus masou masou Juveniles Reared in Water Flow

There is a debate on if aquaculture tank colure could effect survival and growth of fish juveniles,it seems that different fish shows difference in the same tank colure environment or different stage shows difference in the same tank colure. The overall aim of this study is to establish whether tank colure influence survival and growth of Oncorhynchus masou juvenile under artificial controlled conditions. After an 50- days experiment,no significant difference of dead rate was observed in both blue and black tanks,and black tank led to significantly lower final body weight, fork length,as well as SGR. The study shows that rearing in blue tank should be considered little stressful for O. masou masou juveniles and blue material tank should be used in aquaculture practice.

Evaluation of Growth Performance of a Genetically Characterized F1 Rainbow Trout,Oncorhynchus mykiss in a Recirculating Aquaculture System

The growth performance of a selected F1 rainbow trout genetically characterized as polymorphic with locus Omy207UoG (NA = 13, PIC = 0.891, HE = 0.9003) was evaluated in a recirculating aquaculture system (RAS). A set of 157 rainbow trout of 37.8 g of mean body weight and 14.6 cm mean total length per tank, were introduced in each of six fish tank of 5 m3 connected to a recirculating aquaculture system (RAS). The trout was rearing during 317 days. Growth performance indicators and water quality were evaluated during the experiment. The genetically selected F1 rainbow trout showed a tendency towards homogeneity in growth performance along the culture period, reaching a mean total weight of 552.2 g. The length-weight relationship indicated an isometric growth (>3.0). This study presents the basis to establish a long-term marker-assisted selection program for rainbow trout culture in a subtropical region.

Influence of Carvacrol on the Growth Performance,Hematological,Non-Specific Immune and Serum Biochemistry Parameters in Rainbow Trout(Oncorhynchus mykiss)

The present study investigated the effects of phytoadditive carvacrol on growth performance, feed utilization, hematological, non-specific immune and serum biochemical parameters in rainbow trout (Oncorhynchus mykiss). In trial, 240 rainbow trout which had average weight of 10.79 ± 0.57 was used. Fish were divided into four groups before being fed for 60 days with 0, 1 (C1), 3 (C3) or 5 (C5) g/kg of carvacrol. There were no particular differences in the growth performance, feed utilization, whole body composition, hematological parameters between the experimental group and the control group. However, as compared to control group, a significant increase of serum lysozyme activity was seen in groups receiving feed containing C3 and C5 groups after 30 days. The myeloperoxidase activity in groups (C1 and C3) was significantly higher on the 30th day of sampling. Myeloperoxidase activity of C5 treated group was significantly higher on the 60th day in comparison with the control group. Serum glucose levels significantly decreased on 60th day for C1, C3 and C5 treated groups. The serum total protein, globulin and triglyceride levels of C3 treated groups was significantly higher on the 60th day in comparison with the control and other carvacrol treated groups. The level of serum cholesterol in C5 treated groups was significantly lower on the 30th day in comparison with the control and other carvacrol treated groups. The results of the present study indicated that dietary supplementation of 3 g/kg of carvacrol in commercial diets could improve some non-specific and biochemical status in rainbow trout.

Mucosal immune responses to Ichthyophthirius multifiliis in the ocular mucosa of rainbow trout(Oncorhynchus mykiss,Walbaum),an ancient teleost fish

The eye,as a specialized visual organ,is directly exposed to the external environment,and,therefore,it faces constant chal-lenges from external pathogenic organisms and toxins.In the ocular mucosa(OM)of mammals,mucosal-associated lymphoid tissues(MALTs)constitute the primary line of defense.However,the immune defense role of the OM remains unknown in aquatic vertebrates.To gain insights into the immune processes within the OM of teleost fish,we developed an infection model of rainbow trout(Oncorhynchus mykiss)OM using a parasite,Ichthyophthirius multifiliis(Ich).Immunofluorescence,qPCR,and H&E staining revealed that Ich successfully infiltrates the OM of rainbow trout,leading to pathological struc-tural changes,as evidenced by A&B staining.Importantly,the qPCR results indicate an up-regulation of immune-related genes following Ich infection in the OM.Moreover,transcriptome analyses were conducted to detect immune responses and impairments in eye function within the OM of rainbow trout with Ich infection.The results of the transcriptome analysis that Ich infection can cause an extensive immune response in the OM,ultimately affecting ocular function.To the best of our knowledge,our findings represent for the first time that the teleost OM could act as an invasion site for parasites and trigger a strong mucosal immune response to parasitic infection.