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1.
海水经济贝类在海水养殖中占有重要的地位,开展贝类育种、育苗对提高重要经济贝类的产量和质量意义重大。多倍体育种作为贝类育种的方法之一,研究者希望通过这种方法,诱导出个体大、生长快、肉质好的三倍体贝类,以提高群体生长速度,改善经济性状,增强养殖生物的抗逆性。对多倍体贝类的亲贝培育、育种原理、诱导方法、检测技术,以及生物学性状作了综述,最后探讨了多倍体研究中存在的主要问题。  相似文献   
2.
Coffee is one of the historical socioeconomic crops. It has received an increasing attention at the global level, due to its positive interlinkage with the economic growth and on the gross domestic product for most of the producing countries, particularly, developing and least developed countries. Saudi Arabia is one of the coffee producing countries that has a relative comparative advantage of coffee cultivation. Yet, coffee cultivation has not received as much attention in Saudi Arabia as that of producing countries around the world. This study aims to assess the current state of coffee cultivation in Saudi Arabia and to investigate the potential to optimize coffee cultivation in Saudi Arabia that maximizes the net national economic return and export earnings, given limitation of cultivated areas, local market activities, and international trade activities. The study statistically analyzed primary data collected from around (65) coffee farms and traders in the study regions at the south and southwest Saudi Arabia, and optimized coffee cultivation in Saudi Arabia using LINGO optimization software. Empirical results of the study revealed the great potential of Saudi Arabia to expand coffee cultivation at south and southwest regions to meet the escalating local demand and to increase its share at the world market up to 2%. Optimization of coffee cultivation in Saudi Arabia showed a high potential to meet the local demand for coffee by producing 80.07 thousand tons grown over 2861.78 hectares and to generate a net return equivalent to $395.72 million a year, which is equivalent to $138.28 thousand per hectare and $4.94 thousand per ton of coffee. Optimizing coffee cultivation will play a substantial role to increase market share of Saudi Arabia to about 1–2% of the world market by increasing its export volume, respectively, to about 69.66 and 112.56 thousand tons, the national net economic return by about $395.86 and $395.95 million a year, and the export earnings of coffee by about $219.43–354.57 million a year, which in turns, will serve the national strategic trend to diversify the economic base and lower the dependency of incomes generated from oil exportation.  相似文献   
3.
从太平洋深海克拉里昂-克利伯顿断裂带(Clarion-Clipperton fracture zone,简称CC区)4个站位采集的深海沉积物样品中检出26条嘴刺目(Enoplida)线虫个体。综合应用形态学和分子生物学方法,共鉴定嘴刺目线虫6科8属,其中尖口线虫科(Oxystominidae)个体数量最多,占总数的57.7%,其次为前感线虫科(Anticomidae,19.2%)、光皮线虫科(Phanodermatidae,7.7%)、钩线虫科(Oncholaimidae,7.7%)、烙线虫科(Ironidae,3.8%)和矛线虫科(Enchelidiidae,3.8%)。科、属组成与相邻站点同期采样所获的线虫近似,而丰度组成比例有所差异。分子生物学方法获得了线虫rRNA基因序列16条,经Gen Bank数据库比对,其与已有的序列相似性范围为94%—99%,以此为依据可确定到科的水平和大部分属的水平(84.6%)。DNA条形码比对结果和形态学鉴定结果有较高一致性,表明分子条形码技术可作为深海线虫鉴定的有效手段。系统发育分析结果显示,基于18S和28S rRNA基因序列,采用不同方法构建系统发育树,其分支结构基本一致;钩线虫科和矛线虫科聚类在一起,光皮线虫科和前感线虫科聚类在一起,显示出彼此间较近的遗传关系。  相似文献   
4.
This study estimates the economic values of and the dominant contributors to five key ecosystem services of wetlands in Beijing, by using the wetland inventory data in 2014 and economic valuation methods. Results indicate that the 51,434 ha of wetlands in Beijing annually provide 2.07 billion m3 of flood regulation, 944.01 million m3 of water provision, 42,154 tons of chemical oxygen demand (COD) purification, 3.03 PJ of heat absorption, and 9587 ha of habitat. Their economic values are estimated to be 15.89 billion RMB, 1.19 billion RMB, 169 million RMB, 421 million RMB, and 1.08 billion RMB in 2014 (RMB: Chinese currency, US$1 = RMB 6.14), respectively. The total values of five key wetland ecosystem services reach 18.76 billion RMB. In addition, the reservoir and river wetlands in Miyun, Yanqing, Fangshan, Huairou, and Mentougou Districts contribute 78% of key ecosystem services, whereas the urban wetlands in Xicheng, Dongcheng, Haidian, Chaoyang, and Tongzhou Districts more conveniently serve densely local people, hence they should be given particular attentions. In this paper, we develop the valuation methods of wetland ecosystem services, and recommend diversified strategies, regulations, and programs to protect the remaining wetlands in Beijing. This work can also provide a reference for the valuating of wetland ecosystem services for other urban-rural areas.  相似文献   
5.
Although many field trials have been conducted using Bacillus thuringiensis subsp. israelensis (Bti)-based formulations, most have been in rivers with different biotic and abiotic conditions thus rendering the evaluation of their performance very difficult. Recently, results of a threeyear experiment using a new field procedure brought new insight into the behavior and the performance (carry) of two liquid formulations of Bti, Teknar HP-D and Vectobac 1200L, tested in the same lotic environment and under similar abiotic and biotic conditions. Factors such as discharge, water temperature and the hyporheic zone were identified as elements affecting the downstream loss of activity of both products. However, to better understand the reduction of black fly mortality along a stream (measured by using gutters), data of residual dosages of both products (measured by laboratory assay with mosquito larvae) were compared with reduction of black fly mortality. Bti toxic activity was monitored from water samples taken at different distances downstream from an application point, and from probes driven into the hyporheic zone, to study the effects of abiotic factors on the loss of the toxic crystals. Results showed that the loss of dosage was exponential for both products but more crystals were recovered from Vectobac 1200L along the stream than from Teknar HP-D. However, the latter was more efficient, i.e. less toxins were needed to kill 50% of black fly larvae both in temperate (16°C) and warmer (19.5-22°C) water. Also, a rise in water temperature had a greater effect in the kill induced by Vectobac 1200L compared to Teknar HP-D. For the same residual dosages present at the stations, longer carries of toxin activity (higher mortalities) were obtained in warmer water. Finally, the hyporheic zone was identified as a major source of loss of activity of Bti products. Large stream discharges decreased the effect of the hyporheic zone and that was reflected in longer carry of the products.  相似文献   
6.
F/F牙形刺灭绝事件以后,牙形刺很快进入复苏期(王成源、Ziegler,2004)。有关法门期牙形刺的辐射,在国内外的文献中还没有详细的论述或论证。本文基于以前对广西桂林垌村和龙门剖面的牙形刺集群灭绝与复苏的研究,2003年又在垌村剖面加密采样,重点是研究F/F事件后,牙形刺由复苏到辐射阶段的特征,探索牙形刺何时和如何由复苏期进化到辐射期。本文的材料主要是依据华南的资料,特别是本文作者研究多年的垌村剖面的资料。牙形刺的灭绝与复苏是以法门期最主要的属Palmatolepis为主线,在种一级的水平上确定的。法门期牙形刺的辐射同样是以Palmatolepis属内种一级的水平上讨论的。同时也涉及到其它属。本文首次明确提出:牙形刺在晚triangularis带就进入辐射期,因为正是从晚triangularis带,Palmatolepis的minuta,werneri,sandbergi,perlobata,cf.regularis,subperlobata,tenupunctata7个重要种群开始出现,并在法门期中期达到辐射期的高峰。  相似文献   
7.
The remote Pitcairn Group in the South Pacific Ocean comprises a volcanic island (Pitcairn Island), two low coral atolls (Oeno, Ducie) and a raised coralline island (Henderson Island). The geological history of these islands, on anomalously thin oceanic lithosphere, is related to the development of two subparallel island chains (Oeno-Henderson-Ducie; Pitcairn) associated with intra-Pacific plate 'hotspot' activity; the surface manifestation of this activity has been partly determined by structural lineations in the plate inherited from past plate history. The climate of the Pitcairn Islands is determined by the position of the subtropical high pressure system and the South Pacific Convergence Zone. Variations in the strength of this atmospheric circulation system, measured by changes in the Southern Oscillation index of pressure difference, provide a partial explanation of the long-term variability of mean annual rainfall at Pitcairn Island. Knowledge of past climates in the Pitcairn Group remains speculative. Maps of the Pitcairn Islands and a report of climate at Henderson Island (2/91-1/92) are included in the paper.  相似文献   
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9.
随着人民生活水平提高,物质生活富裕,传统家庭结构发生了变化和工作压力的增大,人际关系逐渐趋于淡化,使越来越多的人将感情投注于宠物身上,宠物与人类的关系已经发生了变化,人们越来越注重休闲生活情趣的培养,不再以追求温饱为主要目标,人与宠物间的依赖关系,随着时间的流逝而日益浓厚。饲养的犬猫不再扮演看门和捉老鼠的角色,而是人类休闲时的玩伴。在社会提倡人与人之间关爱的同时,也提升了人们对动物福利的理念,对社会的关爱和爱心,但他们迫切需要兽医医疗、疫病防控和饲养管理的指导。怎样将兽医知识教育公众并增加公众对饲养宠物的理解、对人兽共患病的认识,对所有影响动物福利问题的意识是我们的责任。伴随着宠物数量的增长,围绕宠物经济和宠物行业的发展催生了一些新兴的产业,这些产业带来的不仅是相关产品的诞生,我们看到了这些产业上升的空间和它的发展前途,成就了人们的就业和再就业,同时也给宠物行业带来了不可估量的经济效益,并对社会产生了巨大的社会价值和难以估计的经济产值。目前国内宠物市场已进入一个高速发展的时期,全球发达国家都将目光投向了中国日益增长的消费水平,这也标志着中国宠物市场发展的时机已经成熟。宠物市场涌现出的商机不可小觑,也正是我们看到的中国巨大的商机。以宠物为主题的产业日新月异,中国的宠物行业将迈上一个新的台阶。  相似文献   
10.
Females of an odonate species in which oviposition sites overlap with mating sites may adopt one or more of the following strategies when they lay eggs except when they ‘trade’ mating for access to suitable oviposition sites or for services (guarding, etc.) provided by males: (1) ovipositing at hidden places; (2) ovipositing at a time when males are neither patrolling nor watching; (3) indicating non-receptivity by a behavioral display. The density of ovipositing females of the dragonfly, Cordulia aenea amurensisSelys which was studied between 1970 and 1983 at a pond (Hôrai-numa, Sapporo, Hokkaido) had a high negative correlation with the distance from ‘entrance’ (a part of shore at which the arrival of most adults seems to have occurred). On the other hand, oviposition was rarely observed at a sector being distant from entrance in spite of the inference that larval survivorship was probably high at this sector. Most females oviposited among emergent vegetation in which approach of males to them was difficult, and they scarcely traveled across the open water in search of oviposition sites. Therefore, most females of the population studied were considered to adopt the first strategy. The second and third strategy were not adopted by the population studied. Finally, the influences of some environmental factors and traits possessed by a species on the adoption of these tactics or on the execution of the ‘trades’ were discussed.  相似文献   
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