This study conducted a 70-day feeding trial to evaluate the effects of dietary Lactobacillus plantarum supplementation (0, 0.1, 1.0, and 10.0 g/kg) in red claw crayfish (Cherax quadricarinatus). Growth performance, hepatopancreatic antioxidant-related parameters, and the expression of genes related to the Toll/Imd and JAK-STAT pathways were determined. Results showed that dietary L. plantarum supplementation significantly improved weight gain rate, specific growth rate, daily growth index, and feed efficiency, which were increased by 23.57%, 5.10%, 9.67%, and 7.90%, respectively, and reduced mortality rate by 60.00% compared with the control group (p < 0.05), enhanced the activities of glutathione peroxidase, catalase, superoxide dismutase and total antioxidant capacity, and reduced malondialdehyde levels in the hepatopancreas (p < 0.05). Furthermore, dietary L. plantarum supplementation was associated with the upregulated expression of key genes related to the Toll/Imd and JAK-STAT signaling pathways (p < 0.05). The expression levels of tumor necrosis factor-α, interleukin-1β, and transforming growth factor-β1 were also significantly increased (p < 0.05). Overall, these findings suggest that dietary L. plantarum supplementation improved growth performance and antioxidant-related and immune-related parameters in red claw crayfish, and that these effects were associated with the upregulated expression of genes involved in the Toll/Imd and JAK-STAT pathways. Among the tested treatments, 1.0 g/kg L. plantarum produced the most favorable overall response.

Sterols are essential for the growth and gonadal development of aquatic animals. An 8-week feeding experiment was conducted to investigate the effects of different sterol sources on growth, lipid metabolism, hormone synthesis, and pre-adult testicular development in pre-adult male Cherax quadricarinatus. Five diets were developed for male C. quadricarinatus (11.81 ± 0.29 g), each supplemented with an equal level of sterols (5 g/kg), comprising cholesterol, ergosterol, β-sitosterol, and fucosterol, alongside a control group devoid of supplementary sterols. Compared with the control group, dietary β-sitosterol significantly increased weight gain and specific growth rate. Cholesterol supplementation mainly increased the testicular index and hepatosomatic index. Compared with the other sterol-supplemented groups, the β-sitosterol group exhibited significantly lower serum aromatase activity (P < 0.05), together with significantly higher methyl farnesoate, progesterone, and very low-density lipoprotein levels, while maintaining serum 17β-estradiol and testosterone levels comparable to those of the control group. Serum metabolomic analysis further revealed that dietary β-sitosterol significantly increased the abundance of phosphatidylcholine and phosphatidylethanolamine, and these metabolic alterations were primarily associated with glycerophospholipid metabolism, arachidonic acid metabolism, and autophagy pathways. Overall, among the dietary sterols evaluated under the present experimental conditions, β-sitosterol was associated with favorable growth performance together with coordinated changes in lipid metabolism and steroid hormone-related parameters in pre-adult male C. quadricarinatus.

This study investigated the potential effects of Bellamya purificata polysaccharide (BPP) supplementation in feed on Cherax quadricarinatus, aiming to elucidate its impact on immune function and the underlying regulatory mechanisms. A 60-day feeding trial was conducted to evaluate the effects of varying dietary BPP concentrations (0‱, 2‱, 4‱, 6‱, and 8‱) on growth performance, histopathology, immune function, and transcriptomic profiles of C. quadricarinatus. Dietary BPP significantly increased the final body length and body weight of C. quadricarinatus. Furthermore, BPP inclusion improved the histological damage of hepatopancreatic tissues, alleviated physiological stress, and enhanced antioxidant capacity, antibacterial activity, and anti-inflammatory function, as evidenced by alterations in relevant enzyme activities and gene expression levels. Transcriptomic analysis revealed 957 differentially expressed genes (DEGs), which were predominantly enriched in GO terms and KEGG pathways associated with BPP-mediated immune regulation, such as the PPAR signaling pathway, peroxisome, steroid hormone biosynthesis, and lysosome. In addition, 14 candidate genes were identified, including Acox3, ACOX1, SCP2, and PPT1. Integrated analysis of GO, KEGG, and Short Time-Series Expression Miner (STEM) data supported the development of a mechanistic model illustrating how C. quadricarinatus modulates immune function in response to BPP supplementation. RT-qPCR validation confirmed the accuracy and reliability of the high-throughput sequencing results. Collectively, these findings highlight the potential of BPP as a functional feed additive in aquaculture and provide novel insights into disease prevention strategies for the C. quadricarinatus farming industry.

The objective of this research was to examine how varying dietary inclusion levels of Lactobacillus plantarum influence the muscle composition, hemolymph biochemical indices, lipid metabolism, and the mTOR signaling pathway in red claw crayfish (Cherax quadricarinatus). Four diets with 0 (CK), 0.10 (LG), 1.00 (MG), and 10.00 (HG) g/kg L. plantarum were formulated, with three replicates of 40 crayfish (average weight: 0.13 ± 0.01 g, average length: 0.58 ± 0.01 cm) in a 56-day trial. Results showed that no significant differences in muscle crude protein, crude lipid, ash, or moisture were observed between experimental and CK groups (p > 0.05), while the contents of multiple essential amino acids (e.g., arginine up to 6.05%, histidine up to 7.52%) and non-essential amino acids (e.g., aspartic acid up to 3.70%, glutamic acid up to 1.76%) were significantly elevated, and the content of muscle C18:0 (a saturated fatty acid) was notably reduced (p < 0.05), while total saturated fatty acids showed no significant variation among all groups (p > 0.05). Hemolymph alkaline phosphatase, transaminases, lactate dehydrogenase, and lysozyme activities, as well as glucose, total protein, and albumin levels, were significantly higher in experimental groups (p < 0.05). Lipid metabolism was upregulated, and the mTOR pathway was inhibited in experimental crayfish (p < 0.05). This study demonstrates that dietary L. plantarum enhances lipid metabolism in red claw crayfish, with 1.0 g/kg L. plantarum identified as the optimal supplementation level.

This study investigated the effects of dietary supplementation with the probiotic Enterococcus lactis on coho salmon (Oncorhynchus kisutch). A total of 360 juvenile fish, with an average initial weight of 130.75 ± 1.33g, were randomly assigned to four treatment groups, each with three replicates of 30 fish. The fish were fed for 70 days with diets containing four concentrations of E. lactis: 0 (control), 2×106, 4×108, and 8×1010 CFU/g. We evaluated growth performance, muscle composition, nutrient metabolism, digestive enzyme activity, immune function, intestinal histology, and microbiota structure. Our findings revealed that dietary supplementation with E. lactis significantly improved growth performance and feed utilization compared with the control group (P < 0.05), as indicated by increased weight gain rate (WGR) and specific growth rate (SGR) and reduced feed conversion ratio (FCR). In addition, E. lactis supplementation significantly enhanced muscle nutritional composition by increasing crude protein and crude lipid contents (P < 0.05), and promoted digestive capacity by increasing the activities of digestive enzymes, including lipase and α-amylase (P < 0.05). Moreover, E. lactis supplementation improved antioxidant and immune-related responses, as evidenced by increased activities of superoxide dismutase (SOD), catalase (CAT), and total antioxidant capacity (T-AOC), as well as the regulation of immune-related gene expression, including tlr3, tlr7, lzm, and tgf-β1，and other immune-associated genes (P < 0.05). Furthermore, E. lactis supplementation modulated intestinal microbial composition. The group receiving 4×10⁸ CFU/g showed the most pronounced effects across most measured parameters. These results indicate that dietary E. lactis supplementation, particularly at 4×10⁸ CFU/g, may improve growth performance and physiological status of juvenile coho salmon.

Eicosapentaenoic acid (EPA) and Arachidonic acid (ARA) are essential for gonadal development, while their optimal ratio remains unclear due to their functionally distinct and potentially opposing roles. This study investigated the effects of different dietary EPA/ARA ratios (0.53, 1.12, 1.54, 2.09, and 2.50) on physiological metabolism, ovarian development, reproductive performance, and larval stress resistance in Cherax quadricarinatus (50.72 +/- 0.40 g). The experimental period included nutritional enhancement (6 weeks), mating, spawning, and larval hatching (8 weeks), and an acute ammonia nitrogen stress test (96 h). The initial group comprised crayfish sampled post-acclimatization and prior to nutritional enhancement. Results revealed that the gonadosomatic index was significantly increased in all treatment groups compared with the initial group (P < 0.05). Compared to the control (0.53), dietary EPA supplementation significantly enhanced lipid metabolism in the hepatopancreas and promoted lipid transport to the ovary via the hemolymph (P < 0.05). The contents of progesterone and 17 beta-estradiol in serum were highest in the 2.09 group, notably exceeding those in the control (0.53) (P < 0.05). Moreover, crayfish in the 2.09 group exhibited upregulated expression of citrate cycle-related genes in the hepatopancreas and elevated contents of related metabolites in the ovaries, indicating enhanced energy anabolism (P < 0.05). N-glycan metabolism pathways in the hepatopancreas were significantly enriched in the 2.09 group (P < 0.05), suggesting increased synthesis of exogenous vitellogenin. Additionally, crayfish in the 2.09 group enhanced non-specific immune responses against inflammatory stress by activating the CYP450 pathway and phenoloxidase system (P < 0.05). In summary, a dietary EPA/ARA ratio of 2.09 enhances lipid metabolism, stimulates sex hormone and vitellogenin synthesis, and mitigates inflammatory responses, thereby supporting healthy ovarian maturation and improving reproductive capacity in C. quadricarinatus. Regression analysis estimated the optimal dietary EPA/ARA ratio for promoting ovarian development and reproduction in C. quadricarinatus female broodstock to be between 1.60 and 2.21.

This study investigated the effects of dietary Rhodotorula mucilaginosa supplementation with different concentrations (0.0 g/kg, 0.1 g/kg, 1.0 g/kg, 10.0 g/kg) on red claw crayfish (Cherax quadricarinatus). Four groups were established: control group (CK, 0.0 g/kg), low-dose group (HL, 0.1 g/kg), medium-dose group (HM, 1.0 g/kg), and high-dose group (HH, 10.0 g/kg). The feeding trial lasted for 56 days. The results showed that, compared with the control group, all supplementation groups exhibited significantly reduced feed conversion ratios (p < 0.05). The HM and HH groups demonstrated significant increases in body length growth rate, specific growth rate, weight gain rate, hepatosomatic index, and survival rate (p < 0.05). All supplemented groups showed significantly enhanced trypsin and lipase activities in intestines and trypsin activity in the hepatopancreas (p < 0.05). The HM and HH groups exhibited elevated α-amylase activity in the hepatopancreas (p < 0.05). Compared with the control group, marine red yeast supplementation reduced colonization of potential pathogens while increasing probiotic abundance, effectively improving intestinal microbiota structure. The HM group significantly improved intestinal villus length, width, and muscular thickness (p < 0.05). All supplemented groups showed considerable upregulation of hepatopancreatic genes related to immunity (heat shock protein 70, down syndrome cell adhesion molecule, crustacean antibacterial peptide, serine proteinase inhibitors, crustacean hyperglycemic hormone, anti-lipopolysaccharide factor, lysozyme, and alkaline phosphatase) and antioxidant defense (superoxide dismutase, glutathione peroxidase, glutathione, and catalase) (p < 0.05). These findings indicate that R. mucilaginosa can significantly enhance digestive enzyme activity, maintain intestinal health, improve antioxidant and immune-related gene expression, and promote growth performance in red claw crayfish, with the HM group (1.0 g/kg R. mucilaginosa) showing optimal promotion effects.

This study explored the impact of selenium yeast on the growth performance, body composition, digestive enzyme activity, antioxidant capacity, and lipid metabolism of juvenile GIFT tilapia (Oreochromis niloticus). The study involved juvenile tilapia with an initial average weight of 16.17 +/- 0.65 g, which were fed five different diets containing varying concentrations of selenium yeast (0 g/kg as the control group, and treatment groups receiving 0.1 g/kg, 0.2 g/kg, 0.3 g/kg, 0.4 g/kg, and 0.5 g/kg) over a period of 60 days. The measured dietary selenium concentrations were 0.05 +/- 0.01 mg/kg, 0.26 +/- 0.01 mg/kg, 0.44 +/- 0.01 mg/kg, 0.64 +/- 0.02 mg/kg, 0.87 +/- 0.03 mg/kg, and 1.03 +/- 0.03 mg/kg, respectively. The results indicated that dietary supplementation with selenium significantly enhanced the final body weight, weight gain rate, and specific growth rate compared to the control group (p < 0.05). Additionally, the hepatosomatic index, viscerosomatic index, and feed conversion ratio were significantly reduced (p < 0.05). Whole-body crude protein and selenium contents were significantly increased (p < 0.05) in all selenium-treated groups compared to the control. Moreover, the activities of trypsin, lipase, and alpha-amylase in the intestine were significantly enhanced by selenium supplementation (p < 0.05). At the molecular level, dietary selenium significantly upregulated the expression of catalase, glutathione peroxidase, and glutathione S-transferase in the liver and intestine (p < 0.05). Additionally, it significantly enhanced the expression of acetyl-CoA carboxylase alpha, carnitine palmitoyltransferase, fatty acid synthase, lipoprotein lipase, phosphoenolpyruvate carboxykinase, peroxisome proliferator-activated receptor alpha, beta, and gamma, as well as sterol regulatory element-binding protein 1 in the liver (p < 0.05). In summary, the inclusion of selenium in the diet markedly improved growth performance, digestive enzyme function, serum biochemical profiles, and the expression of genes involved in antioxidant defense systems, along with those regulating glucose and lipid metabolism in juvenile GIFT tilapia. Through quadratic polynomial regression analysis, the ideal dietary supplementation level of selenium for juvenile GIFT tilapia was estimated to range between 0.76 and 0.79 mg/kg.

This study investigated the effects of dietary supplementation with varying levels (CK: 0.0 g/kg; RL: 0.1 g/kg; RM: 1.0 g/kg; RH: 10.0 g/kg) of Rhodotorula mucilaginosa on muscle composition, serum biochemical indicators, antioxidant capacity, lipid metabolism, and the mTOR signaling pathway in red claw crayfish (Cherax quadricarinatus). Results showed that, compared to CK, treatment groups had higher muscle crude protein, fat, leucine, histidine, arginine, and essential amino acids (p < 0.05), and lower saturated fatty acids (p < 0.05). Treatment groups also exhibited increased activities of alkaline phosphatase, acid phosphatase, superoxide dismutase, catalase, glutathione S-transferase, lysozyme, albumin, total protein, and antioxidant capacity (p < 0.05), with reduced activities of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and triglycerides (p < 0.05). In the hepatopancreas, treatment groups showed significant downregulation of AMP-activated protein kinase α, β, and γ, and carnitine palmitoyltransferase 1 genes (p < 0.05). Conversely, genes involved in lipid anabolism (peroxisome proliferator-activated receptor γ, acetyl-CoA carboxylase, fatty acid synthase, sterol regulatory element-binding protein, protein kinase B, and mammalian target of rapamycin 1 and 2) were upregulated (p < 0.05). In conclusion, R. mucilaginosa supplementation affects muscle composition, lipid metabolism, and mTOR signaling. The optimal dose is 1.0 g/kg.

Mannan oligosaccharide (MOS), a prebiotic derived from yeast cell walls, has been shown to enhance growth performance and health status in various aquatic species. As an exogenous antigen adjuvant, MOS modulates T-cell-mediated immune responses, thereby improving immune function and suppressing excessive inflammatory reactions. This study aimed to evaluate the effects of dietary MOS supplementation on growth performance, serum biochemical parameters, muscle composition, digestive enzyme activity, antioxidant and immune status, and the mTOR signaling pathway in juvenile GIFT tilapia (Oreochromis niloticus). Juveniles (initial body weight: 16.17 ± 1.32 g) were randomly assigned to six treatment groups (three replicate tanks per group) and fed diets supplemented with MOS at 0, 0.2%, 0.4%, 0.6%, 0.8%, and 1% (equivalent to 0, 2, 4, 6, 8, and 10 g/kg of diet, respectively) for 60 days. Compared with the control group, fish fed MOS-supplemented diets exhibited significantly higher (p < 0.05) weight gain rates, specific growth rates, and protein efficiency ratios, along with a significantly lower (p < 0.05) feed conversion ratio. Serum albumin, high-density lipoprotein, and lysozyme levels were significantly increased (p < 0.05), whereas triglycerides, low-density lipoprotein, aspartate aminotransferase, and alanine aminotransferase levels were significantly decreased (p < 0.05). In the liver, head kidney, and spleen, the expression of pro-inflammatory genes (tumor necrosis factor α, interleukin 1β, interleukin 6, interleukin 8, and interferon γ) was significantly downregulated (p < 0.05), while the expression of antioxidant and protective genes (superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, nuclear factor erythroid 2-related factor 2, lysozyme, alkaline phosphatase, interleukin-10, transforming growth factor β, and heat shock protein 70) as well as mTOR signaling pathway-related genes (mammalian target of rapamycin, akt protein kinase B, phosphatidylinositol 3 kinase, and ribosomal protein S6 kinase polypeptide 1) was significantly upregulated (p < 0.05). Overall, MOS positively affects tilapia’s growth, health, and immunity, with 0.60% identified as the optimal dietary level based on growth performance.

The objective of the present study was to evaluate the effects of gradient addition of Lactobacillus plantarum to feed on growth performance, digestive enzyme activities, antioxidant capacity, immune response, and intestinal health of red claw crayfish. The experiment comprised four distinct treatment groups: control group (CK, 0 gkg(-)(1)), low concentration group (LL, 0.10 gkg(-)(1)), medium concentration group (ML, 1.00 gkg(-)(1)), and high concentration group (HL, 10.00 gkg(-)(1)). Three biological replicates were established in each group, with each replicate containing 50 juvenile crayfish at the beginning of the experiment, with initial body weights ranging from 0.13 +/- 0.01 g. The experiment spanned 70 days. The experimental results showed that different concentrations of Lactobacillus plantarum significantly increased (p < 0.05) the weight gain rate, specific growth rate, length gain rate, hepatosomatic index, survival rate, and intestinal morphology in red claw crayfish. Additionally, the treatment significantly enhanced (p < 0.05) the activities of lipase, tryptase, and alpha-amylase in the intestine and hepatopancreas, and significantly up-regulated (p < 0.05) the expression of key genes in the hepatopancreas related to antioxidant defense, immunity, and stress response, including superoxide dismutase, glutathione peroxidase, glutathione, catalase, anti-lipopolysaccharide factor, crustacean hyperglycemic hormone, serine protease inhibitors, lysozyme, alkaline phosphatase, down syndrome cell adhesion molecule, antibacterial peptides, and heat shock protein 70. In conclusion, the addition of Lactobacillus plantarum to the feed of red claw crayfish significantly enhanced its growth performance, digestive enzyme activities, antioxidant capacity, and immune response capacity and positively affected its intestinal health. The optimum addition of Lactobacillus plantarum under this experiment was determined to be 1.00 gkg(-)(1) .

In aquaculture, the use of probiotics to improve growth, immunity, and stress resistance in crustaceans has gained increasing attention. This study examined the effects of incorporating different levels of Rhodotorula mucilaginosa (0.0, 0.1, 1.0, and 10.0 g/kg) into the diet on growth performance, antioxidant capacity (AOC), immune function, Toll/Imd, and JAK-STAT signaling pathways in red claw crayfish (Cherax quadricanatus). The investigation was conducted through a 56-day feeding trial. The main results are as follows: Compared with the control group (0.0 g/kg), different R. mucilaginosa levels significantly increased (p < 0.05) the specific growth rate (SGR) and weight gain rate (WGR) of red claw crayfish, significantly increased (p < 0.05) the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), glutathione S-transferase (GST), total AOC (T-AOC), and acid phosphatase (ACP) in hepatopancreas of red claw crayfish, and significantly upregulated (p < 0.05) the relative expression levels of tumor necrosis factor receptor-associated protein 6, akirin, immunodeficiency homolog, interferon regulatory factor 4, Toll-like receptor (TLR) 6, TLR 2, Janus kinase, signal transducer activator of transcription, tumor necrosis factor α, interleukin-1β, transforming growth factor-β1 genes in the hepatopancreas of red claw crayfish. In conclusion, R. mucilaginosa significantly enhanced red claw crayfish's growth, AOC, and immune function, and activated the Toll/Imd and JAK-STAT signaling pathways. In this experimental context, the ideal addition level of R. mucilaginosa is 1.0 g/kg.

The objective of this study was to evaluate the effects of dietary supplementation with different levels of Rhodotorula mucilaginosa (0.0 g/kg, 0.1 g/kg, 1.0 g/kg, and 10.0 g/kg) on resistance to Aeromonas veronii infection in red claw crayfish (Cherax quadricarinatus) (initial body weight of 0.13 ± 0.06 g). The investigation combined a 56-day feeding trial with a subsequent 7-day infection challenge to assess cumulative mortality, immune and antioxidant enzyme activities, and the relative expression of immune-related genes. During the A. veronii infection test, the cumulative mortalities for the 0.1 g/kg, 1.0 g/kg, and 10.0 g/kg groups were 44.44%, 38.89%, and 38.89%, respectively, all significantly lower (p < 0.05) than that of the control group (58.33%). Compared with the control group, after infection with A. veronii, the activities of acid phosphatase, alkaline phosphatase, catalase, and superoxide dismutase in the hepatopancreas and alkaline phosphatase, lysozyme in the hemolymph of red claw crayfish in the 1.0 g/kg group significantly increased (p < 0.05). The activities of aspartate aminotransferase and alanine aminotransferase in the hemolymph of red claw crayfish in the 1.0 g/kg group significantly decreased (p < 0.05). The relative expression levels of serine protease inhibitor, crustacean hyperglycemic hormone, anti-lipopolysaccharide factor, and superoxide dismutase genes in the hepatopancreas of red claw crayfish in the 1.0 g/kg group were significantly upregulated (p < 0.05). In conclusion, R. mucilaginosa could significantly improve the antibacterial ability of red claw crayfish against A. veronii. In this experimental context, the ideal addition level of R. mucilaginosa is determined to be 1.0 g/kg.

Dietary cholesterol and lecithin are two essential nutrients for the growth and health of crustaceans. A 56-day feeding trial was carried out to evaluate the effects of dietary cholesterol and lecithin on the growth performance, antioxidant capacity, intestinal digestive enzymes, and gut microbiota of the Redclaw crayfish, Cherax quadricarinatus. The crayfish (initial average weight 11.39 +/- 0.28 g) were fed with six experimental diets formulated with different contents of cholesterol (0.5% and 1%) and lecithin (1%, 2%, and 3%). No additional cholesterol (0%) and lecithin (0%) were added to the diet of the control group. Crayfish fed the diet with 0.5% cholesterol and 2% lecithin improved growth performance, antioxidant capacity, and intestinal digestive enzyme activities than crayfish fed with other diets. Survival, condition factor, hepatosomatic index, and whole-body proximate composition of crayfish were not significantly affected by different dietary cholesterol and lecithin levels. The Proteobacteria, Firmicutes, and Actinobacteria dominate the gut microbiota community of C. quadricarinatus. In diets with 0.5% cholesterol and 2% lecithin, there were more positive connections and a more complex network structure, which may reduce the risk of pathogen infection. Overall, the combination of 0.5% cholesterol and 2% lecithin in C. quadricarinatus diets was optimal.

The giant freshwater prawn (Macrobrachium rosenbergii), which is widely distributed in Southeast Asia and the western Pacific, is an important commercial prawn species. However, the molecular mechanism of ovarian development is unclear, and there were available data on the ovarian transcriptome of M. rosenbergii is limited. In this study, we constructed transcriptomes of female (ZW) and super female (WW) of M. rosenbergii ovaries to discover genes and pathways related to ovarian development. 71,555 unigenes were obtained, with an average length of 1,530 bp and N50 of 3001 bp. 15,792 (29.3%) unigenes were annotated. A total of 13,610 differentially expressed genes (DEGs) were detected. KEGG pathway analysis showed that multiple pathways related to ovarian development were significantly regulated, such as retinol metabolism, notch signalling pathway, cell cycle, wnt signalling pathway, FoxO signalling pathway, and mTOR signalling pathway. In addition, 12 putative ovarian development-related genes, including FZD9, DDR2, PSMC3IP, CREBBP, DMC1, WBP2NL, DHRS4, SPO11, BCDO2, SDR16C5, CPEB, RDH5, were identified. Our findings will provide a valuable archive for future functional analysis of genes related to ovarian development and future discoveries of the underlying molecular mechanisms of ovarian development.

本研究旨在探究饲料中添加酵母水解物对吉富罗非鱼(Oreochromis niloticus)生长性能、免疫力和抗病力的影响.在基础饲料中添加0(对照组)、0.5％、1.0％、1.5％和2.0％的酵母水解物制成5种实验饲料,对5组初始体重为(25.80+0.45)g的吉富罗非鱼进行为期8周的养殖实验,每组3个重复,每个重复30尾鱼.实验结束后,每个重复选择12尾鱼进行无乳链球菌(Streptococcus agalactiae)攻毒实验,每尾鱼腹腔注射0.2 mL浓度为8.3× 105 CFU/mL的菌液,连续观察14 d,统计累积死亡率.结果 显示,随着酵母水解物添加量的增加,吉富罗非鱼终末体质量(FBW)和特定生长率(SGR)均呈先显著上升(P＜0.05)后下降的趋势.回归分析表明,当SGR达到最大值时,对应的酵母水解物添加量为1.29％.罗非鱼血清一氧化氮合酶、酚氧化酶、酸性磷酸酶、过氧化氢酶和超氧化物歧化酶活性均随饲料中酵母水解物添加量的提高呈先上升后下降的趋势(P＜0.05),添加量为1.5％时达最大值.饲料添加酵母水解物对吉富罗非鱼无乳链球菌的抵抗力有显著影响(P＜0.05),除添加量为0.5％的实验组死亡率与对照组差异不显著外,其他实验组罗非鱼的死亡率均显著低于对照组(P＜0.05).本研究中,饲料添加酵母水解物可有效提高吉富罗非鱼的生长性能、免疫力和抗病力,且在添加量为1.5％时,效果最显著.

为研究红螯螯虾(Cherax quadricarinatus)卵黄蛋白原N端结构域(vitellogenin N domain,VitN)的生物学功能并获得具有免疫特异性的红螯螯虾VitN融合蛋白,试验根据红螯螯虾卵黄蛋白原的mRNA序列(GenBank登录号为AF306784.1)获得VitN mRNA序列(编码第42～585位氨基酸),通过在线分析工具对红螯螯虾VitN进行生物信息学分析,并优化合成红螯螯虾VitN基因序列,构建重组表达质粒pET-28a-VitN,将其转化至大肠杆菌BL21(λDE3)感受态细胞中,经IPTG诱导,对红螯螯虾VitN融合蛋白进行表达、纯化、包涵体复性、Western-blot鉴定和浓度测定.结果表明:编码红螯螯虾VitN的氨基酸共544个,均为常见氨基酸,其中丙氨酸、缬氨酸和丝氨酸含量较多(占比分别为7.72％、7.72％和7.54％),色氨酸含量最少(仅占0.92％);红螯螯虾VitN的相对分子质量为64 681,理论等电点为8.69,共含有8 540个原子,分子式为C2671H4260N758O818S33,不稳定系数为31.49,脂肪系数为74.56,亲水性平均值为-0.45,亲水氨基酸数量明显多于疏水氨基酸数量;编码红螯螯虾VitN的氨基酸全部位于细胞膜外,不存在跨膜区;红螯螯虾VitN亚细胞定位在细胞外或细胞质内,不含常规信号肽,也不含Ⅰ型信号肽酶;红螯螯虾VitN共有67个磷酸化位点,其中丝氨酸磷酸化位点31个,苏氨酸磷酸化位点23个,酪氨酸磷酸化位点13个;红螯螯虾VitN的二级结构包括α-螺旋、β折叠、延伸链、无规则卷曲;三级结构包含具有脂质结合功能的lv-1n和lv-1c肽链结构,且呈现上下两个较为明显的区域,上半部分为sheet折叠结构富集区域,下半部分为α螺旋结构富集区域;在红螯螯虾第129～153位氨基酸和第396～402位氨基酸处各存在一个二硫键.优化后的红螯螯虾VitN基因片段大小约为1 650 bp;经连接、转化、诱导,获得了大小约为64.7 ku的融合蛋白,其在大肠杆菌BL21(λDE3)感受态细胞中的主要表达形式为包涵体;最佳诱导条件为37℃、250 r/min振荡培养至菌液的OD600值达到0.6时,加入诱导剂IPTG至终浓度为0.5 mmol/L,继续于37℃、250 r/min振荡培养4 h;包涵体用Ni-NTA柱纯化时以50 mmol/L咪唑洗脱液的洗脱效果为最佳;经Western-blot鉴定进一步确定该蛋白为 目的蛋白;纯化的红螯螯虾VitN融合蛋白的最终浓度为0.45 mg/mL.说明初步对红螯螯虾VitN进行了生物信息学分析,并成功构建了重组表达质粒pET-28a-VitN,优化了表达系统及纯化方案,获得了具有免疫特异性的红螯螯虾VitN融合蛋白.

为了解稻田养殖红螯螯虾(Cherax quadricarinatus)个体大小与肠道菌群的相关性,实验采用16S rDNA高通量测序和生物信息学技术对稻田养殖红螯螯虾大个体(RB)组和小个体(RS)组肠道菌群的组成、多样性、指示物种、功能等进行比较分析.结果显示:RB组共产生615个OTUs(Operational taxonomic units),RS组共产生602个OTUs,共有OTUs为345个,特有OTUs分别为270个和257个.RB组和RS组的优势菌群相似,门水平主要为变形菌门(Proteobacteria)、软壁菌门(Tenericutes)、厚壁菌门(Firmicutes)等,属水平主要为Candidatus Bacillo-plasma、柠檬酸杆菌属(Citrobacter)、梭菌属(Clostridium)等,但菌群组成存在差异.另外,RB组和RS组的指示物种和菌群代谢功能也存在差异.结果表明稻田养殖红螯螯虾个体大小与肠道菌群组成及其代谢功能有关,在相同的养殖环境和饲养方法条件下,肠道微生物可作为内在因素影响红螯螯虾的生长性能.

[目的]探讨池塘养殖红螯螯虾(Cherax quadricarinatus)个体大小与其肠道细菌间的关系,为筛选虾类肠道有益菌提供参考依据.[方法]提取池塘养殖红螯螯虾后肠样品的总DNA,采用16S rDNA高通量测序技术对其大个体组(PB组)和小个体组(PS组)肠道微生物进行测序,并进行生物信息学分析.[结果]在红螯螯虾后肠样品中,PB组共检出1211个分类操作单元(OTU),PS组共检出587个OTUs,其中365个OTUs为PB组和PS组肠道微生物共有.Alpha多样性分析结果显示,PB组红螯螯虾肠道微生物多样性的Chao1指数、Ace指数和Shannon指数均极显著高于PS组红螯螯虾(P＜0.01).PB和PS组红螯螯虾肠道微生物排名前十位的优势菌群在门、目和属水平上均相似,但菌群组成和指示物种存在差异,其中,在门水平上,PB组的优势菌门为厚壁菌门,占比42.87％,而PS组的优势菌门为变形菌门,占比59.77％;在目水平上,PB组的优势菌目为梭菌目,占比41.25％,而PS组的优势菌目为肠杆菌目,占比57.01％;在属水平上,PB组的优势菌属为梭菌属,占比30.83％,而PS组的优势菌属为柠檬酸杆菌属,占比36.07％;PB组的指示物种是厚壁菌门和浮霉菌门,而PS组的指示物种是变形菌门.此外,PB组和PS组的菌群代谢功能也存在差异,PB组除影响因子和聚糖生物合成与代谢的丰度显著低于于PS组外(P＜O.05,下同),其他代谢(氨基酸代谢、外源生物降解与代谢及萜类化合物和聚酮类化合物代谢等)的丰度均显著高于PS组.[结论]与小个体红螯螯虾相比,大个体红螯螯虾肠道微生物的组成和丰度及其代谢功能明显占优.因此,在相同的养殖环境和饲养方法下,红螯螯虾肠道微生物组成和丰度及其代谢功能是影响红螯螯虾生长性能的内在因素之一.

The fruitless (fru) gene has an important function in the courtship behavior and sex determination pathway of Drosophila melanogaster; however, the fru gene has never been reported in shrimps. In this study, the fruitless-like gene was identified in Cherax quadricarinatus (Cqfru) and is reported here for the first time. A sequence analysis revealed a conserved BTB domain in Cqfru which is the same as fru in D. melanogaster. An analysis of the expression level of Cqfru showed that it was highly expressed in the gastrula stage during embryonic development. Furthermore, in situ hybridization and expression distribution in tissues showed that its sexually dimorphic expression may be focused on the hepatopancreas, brains, and gonads. The gonads, brains, and hepatopancreas of males had a higher expression level of Cqfru than those of females; however, the expression level of the abdominal ganglion was found to be higher in females than in males in this study. The results of an RNA interference treatment showed that a knockdown of Cqfru reduced the expression of the insulin-like androgenic gland hormone (IAG) and tumor necrosis factor (TNF). The characteristic fru gene in shrimps is reported here for the first time, with the results providing basic information for research into the sex-determination mechanism in C. quadricarinatus.