Effect of Chitosan on Intestinal Bacteria of Allogynogenetic Crucian Carp,Carassius auratus gibelio,as Depicted by polymerase chain reaction‐denaturing Gradient Gel Electrophoresis

A 16S rDNA‐based polymerase chain reaction‐denaturing gradient gel electrophoresis (PCR‐DGGE) method was applied to detect intestinal bacterial communities of juvenile allogynogenetic crucian carp, Carassius auratus gibelio, fed with chitosan‐containing diet. This is the first time to use the molecular method to analyze the bacterial communities in the allogynogenetic crucian carp intestine. The DGGE profile with universal bacterial primers revealed simple communities in all treatment groups. Sequencing and phylogenetic analysis of excised DGGE bands showed that the dominant bacteria belonged to class γ‐Proteobacteria and Fusobacteria. The relative abundance and diversity of detected bacteria suggested that 0.5 and 0.75% of chitosan in diet were optimum for juvenile allogynogenetic crucian carp. As in these concentrations, some detected pathogen bacteria either disappeared or decreased. However, the DGGE profile with Aeromonas‐specific primers showed a similar composition among all treatment groups, which suggested that Aeromonas was one of relative stable bacteria components in the intestine of juvenile allogynogenetic crucian carp.     

The impact of net-isolated polyculture of tilapia (<Emphasis Type="Italic">Oreochromis niloticus</Emphasis>) on plankton community in saline–alkaline pond of shrimp (<Emphasis Type="Italic">Penaeus vannamei</Emphasis>)

We used 12 land-based experimental enclosures (6 m × 5 m) in a saline–alkaline pond of shrimp (Penaeus vannamei) to determine the impact of net-isolated polyculture of tilapia (Oreochromis niloticus) on plankton communities for 40 days. Tilapias were stocked in net cages suspended in enclosures, in polyculture ponds including tilapia and shrimp. Four tilapia biomass were tested: 0, 39, 115 and 227 g m⁻². Shrimp stocking biomass were 0.7 g m⁻² in all treatments. There were three replicates in each treatment. Our results showed that the presence of tilapia significantly reduced phytoplankton biomass directly through predation and indirectly through top-down effect. The stocking of tilapia reduced zooplankton biomass, particularly rotifer biomass. However, copepod biomass was not been significantly affected. So, net-isolated polyculture of tilapia can thus have a strong impact on phytoplankton allowing the co-existence of large numbers of copepods with planktivorous fish and improving the water quality of shrimp ponds.     

Mating Systems and Reproductive Success in Hermaphroditic Bay Scallop,Argopecten irradians irradians (Lamarck 1819), Inferred by Microsatellite‐based Parentage Analysis

In this study, we used microsatellite‐based parentage analysis to assess the mating system of a mass spawning bay scallop, Argopecten irradians irradians. Parental assignment was performed on 237 offspring and 14 candidate parents. Overall, 95% of all offspring were unambiguously allocated to their putative parents based on information from six highly polymorphic loci. Offspring from both the self‐fertilization and cross‐fertilization style were observed, the large variation of self‐fertilization rate among individuals displays a mixed mode of mating. The high variances in reproductive success resulted in a decline in effective breeding numbers (N_b/N = 0.71). The self‐fertilization rate was 32.89% for this mass spawning and the coefficient of inbreeding was estimated at around 16.5% per generation. When selfed larvae were removed, the relationship between relatedness and individual reproductive success was proved insignificant between half‐sibings and unrelated, which suggest that selection pressures other than avoidance of inbreeding may be responsible for the evolution and maintenance of the self‐compatible mating system of A. i. irradians. These results lend insight to A. i. irradians cultivation in present China and provide a genetic basis for the development of more effective spawning techniques.     

蒙古鲌食性转变的稳定性同位素研究

采用稳定性同位素分析并结合胃肠内容物鉴定,探讨了小江水域渠马镇至黄石镇段蒙古鲌食物组成。结果显示,体长<200 mm的小个体蒙古鲌δ¹³ C、δ¹⁵ N值分别为(-24.50‰±1.15‰)、(12.17‰±1.54‰),食性类型为杂食性偏肉食性,营养级为2.9;体长>200 mm的大个体蒙古鲌δ¹³ C、δ¹⁵ N值分别为(-23.87‰±1.12‰)、(13.54‰±1.12‰),食性类型为肉食性,营养级为3.3;大个体蒙古鲌δ¹³ C、δ¹⁵ N值极显著大于小个体蒙古鲌(P<0.01),表明蒙古鲌在生长发育过程中发生了食性转变,但部分大个体蒙古鲌和小个体蒙古鲌由于食物来源相同而出现了同位素值重叠现象。     

努力提高农科院所党的建设科学化水平

该文结合中国农科院及其所属研究所党建工作的情况,按照提高党的建设科学化水平的新要求,以科学发展观为指导,深刻理解和正确把握党的建设的科学化内涵,进一步深化对党的建设和执政规律的认识。此外,该文联系实际,分析农科院所党建工作的新特点,找准党建工作着力点,坚持以人为本,加强组织建设,深化创先争优,构建和谐院所,充分发挥党组织的政治核心作用等方面提高党建工作的科学化水平。     

PF455S插秧机及其侧离合器手柄的探讨和改善

PF455S插秧机的行走底盘与国产独轮驱动插秧机相比,水田机动性能和通过性较好,但也存在手柄安装夹紧不当等问题。介绍PF455S动力插秧机的系统组成、设计原理与主要参数,对发现的侧离器手柄问题进行改进,达到了设计目的。     

高校图书馆服务推广探析

服务推广对于吸引读者利用图书馆、改善图书馆的服务工作有着重要的作用。介绍了高校图书馆的服务现状，提出了服务推广应采取的方法，以及在实际工作中应注意的问题。     

基于质粒表达的siRNA对猪圆环病毒2型(PCV2)复制的抑制作用

猪圆环病毒2型(PCV2)是猪圆环病毒相关疾病(PCVAD)的必要病原,对养猪生产构成了严重威胁,但当前缺乏有效的防治手段.为了探索治疗PCVAD的新途径,分别针对PCV2的病毒复制相关蛋白基因(rep)与衣壳蛋白基因(cap),构建了PCV2特异的siRNA表达质粒(pGensil-R259、pGensil-C297和pGensilC490)和PCV2非特异的阴性对照质粒(pGensiI-SCR).在脂质体介导下,将构建的siRNA表达质粒与阴性对照质粒转染PK-15细胞,转染质粒20 h后感染PCV2.结果质粒表达的特异siRNA抑制了PCV2 DNA的合成及Rep和Cap蛋白的表达,使病毒滴度(TCID50)显著下降;针对靶基因不同位点的siRNA的抑制效果不同,病毒感染后36 h内,siRNA对PCV2的抑制作用最强,随后有所下降,但直至感染后60 h仍然能够显著抑制PCV2复制.实验结果提示质粒表达的特异siRNA能够显著地抑制PCV2的增殖,但这种抑制功能与作用时间呈负相关.     

滩鸡实用生产技术

详细介绍了滩鸡品种的选择,育雏的环境条件,雏鸡的选择、饮水和开食,滩鸡的放养及放养过程中青绿牧草和动物小虫子的利用,放养地简易鸡舍的搭建,动物小虫子的繁殖和生产,提高鸡肉风味的3种方法,滩鸡的放养时间和出栏,疾病防控等,目的在于普及滩鸡生产技术,提高广大养殖户的滩鸡生产水平,切实增加农民收入.     

银川盆地富硒土地资源研究

在银川盆地首次发现大面积富硒区.该富硒区具有富硒土层厚、硒含量适中、宜于开发利用等特点.富硒土地分布区不仅硒含量高,而且污染有害元素的含量特别低,呈"原生态"的自然状态.初步分析认为银川盆地土地富硒主要与成土母质(母岩)有关.