Influence of different dietary lipid sources on the growth,tissue fatty acid composition,histological changes and peroxisome proliferator‐activated receptor γ gene expression in large yellow croaker (Pseudosciaena crocea R.)

A 9‐week feeding trial was conducted to investigate the impact of dietary lipid sources on the lipid mechanisms of large yellow croaker by feeding three isonitrogenous and isoenergetic diets containing fish oil (FO), soybean oil (SO) and beef tallow (BT) respectively. The effects of the diets on the growth performance, somatic indices, tissue fatty acid composition, histological changes and peroxisome proliferator‐activated receptor (PPAR)γ expression were evaluated. Experimental diets were all well accepted by fish and no significant (P>0.05) differences were found in the weight gain, growth rate and feed conversion rate. The fatty acid profile of the fish fillet and liver reflected the fatty acid composition of the diets. Specific‐fatty acids were selectively retained, however, in the flesh of the fish; in particular, docosahexaenoic acid and arachidonic acid concentrations were higher than the dietary concentrations. When FO was replaced by SO or BT diets, the reduction in eicosapontaenoic acid in fish tissue was more pronounced, suggesting a preferred utilization of this fatty acid. The consumption of SO displayed intense lipid accumulation in the liver of the fish. The expression of PPARγ increased significantly in the SO group compared with the FO and BT groups (P<0.05).     

Optimal dietary lipid level for large yellow croaker (Pseudosciaena crocea) larvae

A 30‐day feeding experiment was conducted in blue tanks (70 × 50 × 60 cm, water volume 180 L) to determine the effects of dietary lipid levels on the survival, growth and body composition of large yellow croaker (Pseudosciaena crocea) larvae (12 days after hatchery, with initial average weight 1.93 ± 0.11 mg). Five practical microdiets, containing 83 g kg^?1 (Diet 1), 126 g kg^?1 (Diet 2), 164 g kg^?1 (Diet 3), 204 g kg^?1 (Diet 4) and 248 g kg^?1 lipid (Diet 5), were formulated. Live feeds (Artemia sinicia nauplii and live copepods) were used as the control diet (Diet 6). Each diet was randomly assigned to triplicate groups of tanks, and each tank was stocked with 3500 larvae. During the experiment, water temperature was maintained at 23(±1) °C, pH 8.0 (±0.2) and salinity 25 (±2) g L^?1. The results showed that dietary lipid significantly influenced the survival and growth of large yellow croaker larvae. Survival increased with the increase of dietary lipid from 83 to 164 g kg^?1, and then decreased. The survival of larvae fed the diet with 83 g kg^?1 lipid (16.1%) was significantly lower than that of larvae fed other diets. However, the survival in larvae fed the diet with 16.4 g kg^?1 lipid was the highest compared with other artificial microdiets. Specific growth rate (SGR) significantly increased with increasing dietary lipid level from 83 to 164 g kg^?1 (P < 0.05), and then decreased. The SGR in larvae fed the diet with 164 g kg^?1 lipid (10.0% per day) was comparable with 204 g kg^?1 lipid (9.6% per day), but were significantly higher than other microdiets (P < 0.05). On the basis of survival and SGR, the optimum dietary lipid level was estimated to be 172 and 177 g kg^?1 of diet using second‐order polynomial regression analysis respectively.     

Dietary lysine requirement of large yellow croaker (Pseudosciaena crocea,Richardson 1846) larvae

A 30‐day feeding experiment was conducted to estimate the lysine requirement of large yellow croaker larvae (2.75 ± 0.11 mg). Six isonitrogenous (509.5–519.7 g kg^?1 crude protein) and isoenergetic (22.3–22.5 kJ g^?1 energy) microdiets containing graded levels of lysine·HCl ranging from 24.8 to 41.0 g kg^?1 diet in placement of glycine and glutamic acid were formulated. Mixture of crystalline amino acids (MAA) was supplemented to simulate the amino acid (AA) profiles of whole body of this larva, except for lysine. The MAA and supplemented lysine for each diet were coated with tripalmitin. Triplicate groups of 3000 fish were fed to apparent satiation by hand eight times per day. The results showed that specific growth rate (SGR), survival, body composition and the specific activity of digestive enzymes were significantly affected by dietary lysine levels (P<0.05). The optimal dietary lysine requirements estimated by second‐order polynomial model based on SGR and survival were 33.7 (65.5 g kg^?1 dietary protein) and 33.4 (64.9 g kg^?1 dietary protein) g kg^?1 dry diet respectively. The estimated requirements for the other essential AAs were calculated by A/E ratios of whole body AA profile of this larva based on lysine requirement.     

Effects of dietary tea polyphenols on growth,biochemical and antioxidant responses,fatty acid composition and expression of lipid metabolism related genes of large yellow croaker (Larimichthys crocea)

The study was conducted to investigate the effects of dietary tea polyphenols (TP) on growth performance, biochemical and antioxidants responses, fatty acid composition, and lipid metabolism‐related gene expressions of large yellow croaker (Larimichthys crocea). Four diets were formulated with different levels of TP (0.00%, 0.01%, 0.02% and 0.05%). Results showed that growth performance of L. crocea were not different among dietary treatments. Compared with the control group, fish in 0.02% TP group had lower body and hepatic lipid content and lower total cholesterol content. The minimum content of triglycerides and low‐density lipoprotein‐cholesterol were found in 0.05% TP group. Hepatic n‐6 PUFA and n‐3 PUFA were significantly higher in TP supplementation groups. Malondialdehyde content was lower in TP supplementation groups, and superoxide dismutase activity was higher in 0.01% TP group than the control group. The mRNA expressions of carnitine palmitoyltransferase1, acyl‐CoA oxidase and peroxisome proliferators‐activated receptor α were up‐regulated in 0.01% and 0.02% TP groups, while lipoprotein lipase expression was down‐regulated in TP supplementation groups than the control group. Results suggested that 0.01%–0.02% TP supplementation could reduce the deposition of liver lipid of L. crocea caused by high‐lipid diet, which might be due to the increase in lipid oxidation related gene expressions.     

Evaluation of Enteromorpha prolifera as a feed component in large yellow croaker (Pseudosciaena crocea,Richardson, 1846) diets

A 9‐week feeding trial was conducted to investigate the effects of dietary Enteromorpha prolifera on the growth performance and body composition of juvenile large yellow croaker (Pseudosciaena crocea) (Richardson, 1846) (11.41 ± 1.59 g) in floating sea cages (1.5 × 1.5 × 2.0 m). Four isonitrogenous and isoenergetic diets were formulated to contain graded levels (0%, 5%, 10% and 15%) of E. prolifera. Survival ranged from 98.7% to 99.7%, and was independent of dietary treatment (P>0.05). There were no significant differences in the feeding rate among dietary treatments (P>0.05). The specific growth rate (SGR) increased with increasing levels of E. prolifera. When the supplementation of E. prolifera was >5%, SGR was significantly higher compared with the control group (0%). The feed efficiency ratio (FER) in fish fed the diet with 5%E. prolifera (diet 2) was higher than that of the other groups, while in fish fed the diet with 10%E. prolifera (diet 3), it was the lowest (P<0.05). The protein retention (PR) decreased as the level of E. prolifera increased in diets (5%, 10% and 15%). The protein body content displayed a trend similar to that of PR. No significant difference was observed in body moisture and ash among the dietary treatments. An increase in minerals of potassium, magnesium and sodium in body was observed with an increase in dietary seaweed concentrations. On basis of the SGR and FER, supplementation levels of E. prolifera can reach at least 15% without affecting the growth and still maintain a high survival rate for juvenile large yellow croaker.     

突变高温胁迫对大黄鱼血清生理指标的影响

鱼类作为变温动物,在水温突变时体内会发生一系列生理变化。本研究分析了突变高温胁迫下大黄鱼幼鱼血清皮质醇(COR)、血糖(GLU)以及乳酸(BLA)含量的变化规律。实验选取8月龄平均体重为(118.8±6.05)g的大黄鱼作为实验对象,对照组设定温度为(23±0.3)℃,实验组设定温度为(33℃±0.3)℃,变温过程为突变,观察记录实验现象。结果表明:大黄鱼幼鱼在33℃高温胁迫下有强烈的应激反应,表现为呼吸加快、极度不安、游动剧烈。经33℃高温胁迫2 h后,实验组幼鱼血清中皮质醇、血糖、乳酸含量与对照组相比均有显著的升高(P0.05或0.01),陆续出现死亡,最终全部死亡。研究认为,33℃高温胁迫对大黄鱼有致命的影响,在养殖生产过程中要将水温严格控制在33℃以下。     

Influence of dietary biotin levels on growth and non‐specific immune response in large yellow croaker,Larimichthys crocea R

A 9‐week feeding experiment was conducted to determine the effect of dietary biotin levels on growth performance and non‐specific immune response of large yellow croaker. Fish (6.16 ± 0.09 g) were fed twice daily to apparent satiation with diets containing 0.00 (as the basal diet), 0.01, 0.05, 0.25, 1.24 and 6.22 mg biotin kg^?1 diet. Results showed that fish fed the basal diet had the lowest survival rate, and fish fed 0.05 mg kg^?1 dietary biotin achieved significantly higher final weight and weight gain. Dietary biotin levels had no significant influence on carcass crude lipid, moisture and ash content, but significantly influenced the carcass crude protein. Liver biotin concentration significantly increased with the supplementation of biotin, but no tissue saturation was found within the supplementation scope of biotin. Broken‐line regression analysis of weight gain showed that juvenile large yellow croaker requires a minimum dietary biotin of 0.039 mg kg^?1 for maximal growth. The analyses of serum parameters showed that the moderate‐ (0.05 mg kg^?1) and high‐dose (6.22 mg kg^?1) dietary biotin significantly improved both lysozyme and alternative complement pathway activities, indicating dietary biotin within a certain range could improve the non‐specific immune response of large yellow croaker.     

大黄鱼网箱养殖水体的细菌群落结构

以16S rDNA为分子标记, 通过构建克隆文库、限制性片段长度多态性(Restriction Fragment Length Polymorphism, RFLP)分析等技术手段, 研究大黄鱼(Larimichthys crocea)网箱养殖水体中细菌的群落结构。样品采自福建省宁德市三都湾富发养殖基地。随机选取5个不同养殖网箱水样混合, 取3 L混合水样过滤富集细菌后提取总DNA, 用细菌通用引物27F和1 492R扩增其16S rRNA基因, 构建克隆文库。从文库中随机挑选154个克隆子进行分析, 得到137个阳性克隆, 92种RFLP带型。对部分代表性克隆子进行测序的结果表明, 大黄鱼养殖水体中细菌多样性非常丰富。序列分析结果显示, γ-变形菌纲的假交替单胞菌属(Pseudoalteromonas)细菌为最优势菌(占γ-变形菌纲克隆子数的31.2%), 海源菌属(Idiomarina)次之(占γ-变形菌纲克隆子数的15.1%)。此外还存在6.6%的厚壁菌门(Firmicutes)、5.9%的拟杆菌门(Bacteroidetes)、各0.7%的浮霉状菌门(Planctomycetes)、绿屈挠菌门(Chloroflexi)、绿菌门(Chlorobi)细菌和OP11类群。本研究结果阐明了网箱养殖大黄鱼水体细菌的群落结构, 为大黄鱼养殖区病害防治、环境监测以及探讨大黄鱼健康养殖与养殖水体细菌间的关系奠定了基础。     

大黄鱼ATG5基因的分子特征及促进病毒增殖的作用研究

自噬是维持真核细胞稳态的重要过程，在细胞分化、发育、免疫等生理过程中发挥作用。目前，人们对于自噬相关基因（Autophagy related gene，ATG）在鱼类免疫应答中的功能仍知之甚少。本研究从大黄鱼（Larimichthys crocea）中克隆得到了自噬相关基因ATG5（LcATG5），其开放阅读框（ORF）全长828个核苷酸，编码275个氨基酸的蛋白质，预测的分子量为32.3 kD，等电点为5.7。氨基酸序列比对和系统进化分析结果显示，LcATG5与其他物种ATG5之间的序列一致性较高，含有1个高度保守的APG5结构域，并且与棘头梅童鱼（Collichthys lucidus）ATG5的亲缘关系最近。荧光定量PCR结果表明，LcATG5在所检测的11个组织或器官中均有表达，在血液中表达量最高，在脾脏中表达量最低；LcATG5在来源于大黄鱼头肾组织的原代粒细胞、淋巴细胞和巨噬细胞以及细胞系LYCK细胞中也均有表达，在原代粒细胞中表达量相对较高，而在巨噬细胞中相对较低；病毒类似物poly(I:C)刺激后，这4种免疫细胞中LcATG5的表达水平都显著上调，其在LYCK细胞中变化最为显著，刺激后12 h上调了3.93倍。过表达LcATG5的鲤上皮瘤（Epithelioma papulosum cyprinid, EPC）细胞受鲤春病毒血症病毒（Spring Viremia of Carp Virus, SVCV）感染48 h后，细胞病变效应（Cytopathic effects, CPE）明显高于对照组，细胞培养上清中SVCV的滴度为1013.82 TCID50/Ml，高于对照组109.27 TCID50/mL，同时细胞内SVCV标志基因SVCV-G、SVCV-M和SVCV-P的表达量分别上调了13.77倍、15.72倍和11.39倍，表明LcATG5过表达促进了EPC细胞中SVCV病毒增殖，这些结果为深入研究自噬和自噬相关基因在鱼类病毒感染过程中的作用及机制奠定了基础。     

Oral bovine serum albumin immune‐stimulating complexes improve the immune responses and resistance of large yellow croaker (Pseudosciaena crocea,Richardson, 1846) against Vibrio alginolyticus

This study aimed to investigate effects of bovine serum albumin immune‐stimulating complexes (BSA ISCOMs) on immune‐related genes expression, serum nonspecific immunity and disease resistance of large yellow croaker (Pseudosciaena crocea). Fish were fed diets containing 3.5 ml of BSA ISCOMs per kg feed (experimental group) or 3.5 ml of phosphate‐buffered saline per kg feed (control group) for 1 week. The liver, spleen, head‐kidney tissues were sampled for determining gene expression of myxovirus‐resistant protein (Mx), major histocompatibility complex class II alpha chain (MHC II α), tumour necrosis factor‐alpha (TNF‐α) and interleukin‐10 (IL‐10) 30 and 90 days after feeding. Also, blood samples were collected for determining activities of serum superoxide dismutase (SOD), interferon alpha (IFN‐α), TNF‐α and alkaline phosphatase (ALP). TNF‐α and MHCⅡα gene expression in the liver, spleen, head‐kidney, as well as IFN‐α, TNF‐α and ALP activities in the serum, of experimental fish were significantly higher 30 days after feeding; while only TNF‐α and MHC II gene expression in the head‐kidney remained upregulated 90 days after feeding. The cumulative mortality of the experimental fish was significantly lower than control. This study indicated that BSA ISCOMs improved the immune response and induced protective immunity in large yellow croaker.     

Effects of dietary lutein/canthaxanthin ratio on the growth and pigmentation of large yellow croaker Larimichthys croceus

This study was conducted to investigate the effects of dietary lutein/canthaxanthin ratio on the growth and skin coloration of large yellow croaker. Five carotenoids supplemented diets were formulated to contain 75/0, 50/25, 37.5/37.5, 25/50 and 0/75 mg kg^?1 of lutein/canthaxanthin. The diet without carotenoids supplementation was used as the control. Fish of the similar size (13.83 ± 0.04 g) were fed with these experimental diets for 8 weeks in sea cages. Results showed that there were no significant differences in survival rate, specific growth rate and feed conversion ratio among the all treatments (P > 0.05). The ventral skin lightness was not affected by dietary treatments (P > 0.05). However, the dorsal skin lightness in the treatment of control was significantly lower than those in the treatments with supplemented dietary carotenoids (P < 0.05). The lowest values of yellowness, redness and carotenoid content both in ventral and dorsal skin were found in the control. Yellowness and carotenoid content both in ventral skin and in dorsal skin decreased with the decreasing of the proportion of dietary lutein. Meanwhile, the redness increased with the increasing of the proportion of dietary canthaxanthin. Fish fed with the control diet had higher melanin content in the dorsal skin, although no significant differences were found. Coloration parameters were linearly related to the carotenoid content in skin. Meanwhile, yellowness, redness and carotenoid content were linearly related to the proportion of dietary lutein. In conclusion, under present conditions, both lutein and canthaxanthin are needed in the diet for large yellow croaker. Compared to the lutein, higher dietary canthaxanthin contents are better for the skin redness.     

Effects of antimicrobial peptide APSH‐07 on the growth performance,anti‐oxidation responses,stress resistance and intestine microbiota in large yellow croaker Larimichthys crocea

A 65‐day feeding trial was conducted to investigate the effects of dietary antimicrobial peptide APSH‐07 on the growth performance, anti‐oxidation responses, stress resistance and intestine microbiota of large yellow croaker Larimichthys crocea. Four isonitrogenous and isolipidic diets were formulated with 0, 30, 60 and 90 mg/kg of APSH‐07, respectively. The results showed that the fish fed with 90 mg/kg of dietary APSH‐07 had the significantly highest specific growth rate (p < .05). The activities of catalase, superoxide dismutase, the total anti‐oxidative capacity and lysozyme had the significantly highest values in liver of fish fed with 90 mg/kg of dietary APSH‐07 (p < .05). Serum glucose increased significantly in fish fed diets without APSH‐07 supplementation after temperature stress, while serum cortisol increased significantly in those after trawl stress (p < .05). Fish fed with 90 mg/kg of dietary APSH‐07 showed significantly higher operational taxonomic units, ACE estimator and phylogenetic diversity whole tree in intestine microbiota compared to fish fed without APSH‐07 (p < .05). In conclusion, under the present experimental condition, 90 mg/kg of antimicrobial peptide APSH‐07 supplementation in diet had the better growth performance, higher anti‐oxidation and stress resistance capacity, and a potentially more beneficial intestine microbial community of large yellow croaker.     

Effects of dietary carbohydrate and lipid levels on growth performance,feed utilization,body composition and non‐specific immunity of large yellow croaker (Larimichthys crocea)

The present study was conducted to investigate the effects of dietary lipid, carbohydrate and their interactions on growth performance, feed utilization, body composition and non‐specific immunity of large yellow croaker (Larimichthys crocea). The experimental fish were fed the diets with graded levels of dietary crude lipid (80, 110 and 140 g/kg diet) and dietary carbohydrate (60, 90 and 120 g/kg diet) for 7 weeks. Results showed that the specific growth rate decreased significantly as dietary carbohydrate increased, which partly resulted from the progressively reduced feed intake and protein efficiency ratio. Meanwhile, the result of postprandial glucose content confirmed glucose intolerance of the croaker. However, the specific growth rate was not significantly altered by dietary lipid, but the feed intake was remarkably reduced. The different growth performance and feed utilization of croaker in response to dietary lipid and carbohydrate resulted in the variation of body composition. In addition, the activity of lysozyme and classical complement pathway was significantly improved in croaker fed the diet with 110 g/kg lipid. In above, dietary carbohydrate and lipid of large yellow croaker should be maintained at 60 and 110 g/kg diet, respectively, based on the above indices.