Growth performance and whole‐body composition of yellow catfish (Pelteobagrus fulvidraco Richardson) under feeding restriction

Fish growth is an important index in aquaculture practice. However, the effect of growth under restricted feeding on quality of fish grown to the same size remains poorly unknown. In this study, yellow catfish were reared by feeding them at three different feeding rates such as low (FR‐L group), medium (FR‐M group) and high (apparent satiation) ration levels for 82, 58 and 34 days to reach the same size, respectively. After this period, the growth performance, whole‐body amino acid composition and fatty acid profile of the fish were evaluated. Feeding restriction led to significant decreases in specific growth rate and feed conversion efficiency. Significant increases in dry matter, protein and energy contents were observed in fish under both restricted feeding treatments. FR‐L‐treated fish had significantly lower whole‐body essential amino acid contents, and significantly higher Ala and non‐essential amino acid contents compared to fish fed to satiation. Fish in restricted feeding treatments had significantly higher n‐3 PUFA and n‐3/n‐6 ratio compared to the fish fed to satiation. The present results indicate that from a quality perspective, there are certain advantages in improvement of whole‐body composition and enrichment of n‐3 PUFA associated with the restricted feeding of yellow catfish at slow growth rate.     

褐藻多糖硫酸酯降解及其产物活性研究进展

<正>褐藻多糖硫酸酯广泛存在于海藻和海洋棘皮动物中,Kylin于1913年首次从掌状海带(Laminaria digitata)中提取并成功分离出了L-岩藻糖,将其命名为fucoidin;后许多研究者经热水法、酸法、酶法提取分离表明,褐藻多糖硫酸酯除岩藻糖和硫酸基团外,还含有甘露糖、半乳糖、木糖、葡萄糖、鼠李糖及糖醛酸等成分,确定了褐藻多糖硫酸酯杂多     

Effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco (Siluriformes, Bagridae, Pelteobagrus)

The present experiment was conducted to investigate the effects of dietary protein to carbohydrate ratios on growth and body composition of juvenile yellow catfish, Pelteobagrus fulvidraco . Nine diets were formulated to contain three protein levels (30%, 36% and 42%), each with three carbohydrate levels (24%, 30% and 36%). Each diet was randomly assigned to triplicate groups of 20 fish (initial mean body weight: 8.24±0.20 g) in indoor flow – through fibreglass tanks. The experiment continued for 8 weeks. Weight gain and specific growth rate were similar for the fish fed the 36% and 42% protein diets but higher than that fed the 30% protein diet. At the 36% protein level, carbohydrate contents varying from 24% to 36% ( P / E ratio of 24.0–28.2 mg protein kJ⁻¹) had no significant effects on growth performance and feed utilization ( P >0.05). Protein efficiency ratio tended to increase with dietary carbohydrate level at the same protein level. Dietary treatments significantly influenced body composition ( P <0.05), but not the condition factor, viscerosomatic index, hepatosomatic index and intraperitoneal fat ratio ( P >0.05). Based on these observations, 36% protein and 24–36% carbohydrate with the P / E ratio of 24.0–28.2 mg protein kJ⁻¹ seemed suitable for optimal growth and feed utilization, and carbohydrate could cause protein-sparing effect in diets for juvenile yellow catfish.     

长江口海域营养盐的形态和分布特征

利用2007年4月对长江口海域航次的调查结果,对该海域营养盐的形态和分布特征进行了探讨,并对其主要控制过程进行了讨论.结果表明:长江口海域营养盐的浓度变化范围较大,整体分布趋势是由近岸向外海逐渐降低,且明显受水文状况影响.在长江口海域,磷主要以磷酸盐的形式存在,其余依次是溶解有机磷、颗粒态磷;氮主要以硝酸盐的形式存在,其余依次是溶解有机氮、颗粒态氮、氨氮、亚硝酸盐.硝酸盐和硅酸盐的行为是保守的,其行为主要受咸淡水混合过程控制;磷酸盐、溶解有机磷、颗粒态磷、亚硝酸盐、氨氮和溶解有机氮的行为是非保守的.     

AFLP分子标记技术及其在水产动物中的应用

AFLP分子标记技术是DNA指纹技术的重大突破,由于其快速、简便、有效,因而在医学、农业、林业、畜牧业、渔业等领域中得到了广泛的应用。近年来人们不断地将这一技术完善和发展,使得AFLP成为迄今为止最有效的分子标记。本文简述了AFLP技术的基本原理、技术流程以及在水产动物中的应用情况。     

Two biomass preparation methods provide insights into studying microbial communities of intestinal mucosa in grass carp (Ctenopharyngodon idellus)

Animal digestive tract is habitat for a large number of autochthonous microbiota, which play central roles in multiple biological and physiological processes of the host. In this study, two different micro‐biomass preparation methods were employed to evaluate the diversity of intestinal mucosa‐associated microbiota in grass carp (Ctenopharyngodon idellus). Genomic DNAs were isolated either directly from intestinal mucosal samples (group A), or from micro‐biomass after microbial dissociation (group B). Community richness, diversity and evenness indices were all higher in group B, but differences were not statistically significant (P = 0.97, P = 0.33, P = 0.34 respectively). Furthermore, group B samples exhibited an increased ratio of bacterial DNA in comparison with group A samples, but the difference was also not statistically significant (P = 0.74). In addition, there were no statistically significant differences between the two groups (P > 0.05) at the taxonomic level. Our results support previous findings that there exists a great abundance of the intestinal mucosa‐adherent microbiota in the grass carp; among these, Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, Spirochaetes and Fusobacteria were the most common phyla. Within these microbiota, Paenibacillus, Bacteroides, Bacillus and Cetobacterium genera comprise the majority of the community, implicating their functional importance (e.g. as probiotics) to their host. Our results contribute towards a better understanding of the intestinal microbial profile of grass carp. Both micro‐biomass preparation techniques proved to be feasible for studying mucosa‐adherent microbiota of grass carp; however, the second method (group B) provides a protocol that is somewhat more effective than the first method (group A).     

APETALA1基因启动子的克隆与功能分析

为了分析AP1的表达调控模式,本研究克隆了拟南芥花异常株系AFDL的AP1启动子,启动子元件预测结果表明:AP1启动子中含有3个结合MADS调控因子的CArG box(从5'依次编号为CArG1、CArG2、CArG3),通过删减AP1启动子长度以及改变CArGbox数量构建了5个GUS表达载体并转化野生型拟南芥.测序结果显示:AFDL的AP1启动子在核苷酸序列上与野生型拟南芥完全一致,这表明AP1在AFDL中的表达显著降低并不是启动子序列突变引起的;转基因植株的GUS表达模式说明了CArG1在花发育早期及后期激活基因的表达,CArG2在整个后期都对基因的表达有抑制作用,而CArG3在花发育初期就能抑制基因的表达,并且在中后期仍然保持了对下游基因的抑制作用,CArG box1、2、3对AP1的表达有显著但非决定性的影响.此外,还推测在AP1启动子0～-3 579 bp范围之外存在影响AP1在第4轮花器官表达的调控元件,-3 579 bp至-1 752 bp区域可促进AP1的表达,而AP1启动子-1759 bp至-1359 bp区域除CArG2外的其它元件对调节其表达无明显作用.     

塑料大棚盐渍化土壤灌水洗盐对水环境污染负荷的研究

针对塑料大棚盐渍化土壤常用的灌水洗盐方式,通过小区和原状土柱模拟灌水洗盐试验,研究了灌水洗盐降低土壤盐渍化的效果及其通过径流和渗漏流失对水环境的氮磷污染负荷。结果表明：灌水洗盐能降低表层土壤盐分53%～64%、土壤硝态氮55%～60%,但使表层土壤速效磷增加了1.0～1.5倍;洗盐过程中通过径流和渗漏流失进入水环境的氮磷污染负荷为硝态氮7.66 kg/hm²、铵态氮0.77 kg/hm²、总氮12.71 kg/hm²和总磷1.27 kg/h     

一步法快速构建长片段RNAi发夹的载体

利用RNA干扰(RNA interference,RNAi)技术可以进行基因功能研究以及作物遗传改良,但常规构建RNAi载体方法费时费力.本研究报道了一种基于USER酶一步法快速构建RNAi发夹结构的载体2301/RNAi/OS及其应用方法,操作简便,省时省力.与已报道的利用酶切连接、Gateway兼容的同源重组或PCR直接连接等构建RNAi载体相比,该载体不需要酶切片段,片段扩增完成后即可与制备好的线性化载体进行反应,缩短操作流程和时间,提高成功率;该载体对插入片段的酶切位点和长度没有要求,理论上任何位置和长度的片段均可进入2301/RNAi/OS载体中,尤其是长片段RNAi的构建.本试验以本氏烟(Nicotiana benthamiana)PDS(Phytoene desaturase)基因为例,利用农杆菌介导的瞬时表达体系验证了该RNAi能够在植物体内有效地实现基因沉默.该载体以新霉素磷酸转移酶基因(NPTII)作为筛选标记基因,可以利用卡那霉素(Kanamycin)和G418(Geneticin)等抗生素筛选转基因阳性植株,适合单子叶和双子叶植物的遗传转化.