Improving growth performance and caudal fin stripe pattern in selected F6–F8 generations of GIFT Nile tilapia (Oreochromis niloticus L.) using mass selection

Genetic improvement using the mass selection method of growth performance and stripe pattern on caudal fin in selected F₆, F₇ and F₈ generations from genetically improved farmed tilapia strain Nile tilapia was evaluated at the National Tilapia Seed Farm of Qingdao, north China. In experiment I (2003), the average of daily body‐weight gain of F₇ was 12.5% higher than F₆, and 28.6% higher than F₅ (P<0.05). In experiment II (2004), the average daily body‐weight gain of F₈ was 12.9% larger than F₇, and 56.9% larger than F₆ (P<0.05). Coefficient of variation [(SD/mean)100] of body weight of F₈ decreased significantly (P<0.05) to 79.7% of F₆ and 72.9% of F₇, respectively, indicating that the growth became more synchronous after continuous selection. The percentage of fish with ideal vertical and parallel stripes on caudal fins in F₅, F₆, F₇ and F₈ reached 24.8%, 28.8%, 32.2% and 37.6%, respectively, significantly higher than that of the base population (17.6%) (P<0.05).     

四带小鲃的长鳍表型及其转录组分析

四带小鲃（Puntius tetrazona）是一种具有较高经济价值的小型热带观赏鱼。我们对野生型和长鳍突变型四带小鲃的体长、尾鳍长、尾鳍分节数目和分节长度共4个指标进行了统计分析。结果显示,6月龄野生型（n = 30）与突变型（n = 30）成鱼体长没有显著差异（P = 0.904 2）,但两者在尾鳍长、尾鳍分节数目和分节长度3个指标存在显著差异（P < 0.000 1）。同时,我们对不同体长野生型（n = 80）和突变型（n = 80）尾鳍长度、分节数目和分节长度进行了线性回归分析,结果显示,相对于野生型,突变型尾鳍长度增加速率更快（野生型：k = 0.28,突变型：k = 0.62,P < 0.000 1）,尾鳍分节数目增加频率基本一致（野生型：k = 0.79,突变型：k = 0.82,P = 0.006）,尾鳍分节长度更长（野生型：k = 0.006 8,突变型：k = 0.000 4,P < 0.000 1）。野生型和突变型成鱼尾鳍组织的转录组分析结果显示,转录组从头组装共获得56 271个unigene,野生型组（n=3）和突变型组（n=3）之间共有1 304个差异表达基因,其中971个基因上调,333个基因下调。差异表达基因 KEGG通路显著富集到细胞周期和DNA复制等与细胞增殖相关的信号通路,其中细胞周期蛋白（cyclin A,cyclin B和cyclin E）和细胞周期依赖性激酶（cdk1）等基因显著上调。最后,对ckap2l、ki-67、cdc20、prc1、urgcp和cdks共6个基因的表达水平进行了qRT-PCR分析,其结果与转录组分析基本一致。以上结果表明,长鳍四带小鲃突变基因引起细胞周期相关基因表达量上升,造成尾鳍分节片段的细胞增殖速率加快,尾鳍分节长度增加,呈现为长尾鳍表型。本研究结果为鉴定突变基因和揭示长尾鳍形成的分子机制奠定基础。     

Diversity and origins of giant guitarfish and wedgefish products in Singapore

1. Giant guitarfishes (Glaucostegidae) and wedgefishes (Rhinidae) are some of the most threatened marine taxa in the world, with 15 of the 16 known species exhibiting global population declines and categorized as Critically Endangered according to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. The recent inclusion of all species in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) necessitates more rigorous enforcement by regulatory authorities.
2. Challenges in regulating the trade of giant guitarfish and wedgefish products due to difficulties in visual identification of processed products and labelling issues impede enforcement. The aim of this study is to characterize the diversity and origins of associated traded products that were commercially available in Singapore, one of the world's top importers and re-exporters of shark and ray products.
3. A total of 176 samples of elasmobranch products were obtained between June and December 2019 from fishery ports and various retailers in Singapore. By applying cytochrome c oxidase subunit I gene barcoding, 31 elasmobranch species were detected, with 55% of the species considered threatened (Critically Endangered, Endangered, or Vulnerable) based on the IUCN Red List and 35% of species listed in CITES Appendix II. Four species of giant guitarfishes and wedgefishes were commercially available to consumers in fresh forms of whole fish, fillet, and fin, as well as dried and cooked meats.
4. DNA barcoding has proven to be an effective tool for identifying elasmobranch products that are impossible to recognize visually and would aid enforcement of CITES trade regulations. This work underscores the urgent need to step up enforcement of marine wildlife regulations and draw public attention to the elasmobranch trade.

     

西江林场杉木的经济轮伐期

根据市场趋势调整林业经营对策,是林业生产的重要课题,而各类用材林经济轮伐期的确定则是重中之重．就此,根据西江林场近10 a来杉木用材林调查数据和有关资料,用土地纯收益法、内部收益率模型、净现值一般模型处理计算,对西江林场杉木林用材林的经济轮伐期作了初步探讨,得出杉木轮伐期为13-15 a．依此可大大缩短杉木林的经营周期,对加速资金周转,提高经营效益,解决两危问题增强林业生产积极性和活力等都有一定的作用．     

拖拉机用冷轧翅片管式散热器的设计与试验

设计了一种以冷轧翅片管为冷却元件的拖拉机用柴油机散热器。以冷轧翅片管代替扁管管片芯子结构。散热器外壳及其附属元件不作任何改变，便于加工和推广应用。在试验台上的试验表明，散热效果显著。     

NUMERICAL STUDY OF FLOW AND HEAT TRANSFER IN AN INCLINED RECTANGULAR FIN GROOVE

Flow and heat transfer are numerically studied in a rectangular fin groove when the fin base is heated with contsant temperature. Rayleigh number, inclination , aspect ratio, thick ness and conductivity of the fin are systematically changed to examine their effects. Five flow patterns are found, local and average characteristics are given, and the mechanism of heat transfer is discussed. The results can be used as a reference for fin designs.     

冷库冰水混合间接换热器的传热与流动特性

北方地区冬季寒冷漫长,夏季炎热,冬季储冰夏季利用有利于节能减排。利用冰水混合间接换热系统进行冷量交换,不仅节能环保而且空气质量明显提高。采用有限体积法商业软件FLUENT,应用SIMPLE算法对翅片管式换热器平直翅片的换热与流动特性进行数值研究,计算结果与试验结果对比分析。结果表明:数值模拟与试验偏差不超过15%;迎面风速均匀分布情况下,随着迎面风速的增加,换热系数和压降分别增加了133%和428%;平均场协同角随迎面风速的增加而增大,速度场和温度场的协同程度变差,对换热不利;在相同的空气体积流量下,迎面风速沿冰水流动方向呈逐渐降低的分布方式对换热有利。     

促进天祝县草地畜牧业向“两高一优”方向转移的几点思考

根据社会主义市场经济的新形势，结合天祝牧业县的具体条件，提出了天祝县草地畜牧业向高产、优质、高效方面转移的几点具体意见。