Exchanging gifts at the holidays is a tradition that dates back to thousands of years ago.Children are typically excused from buying gifts because they cost money kids may not have.But the truth is that some of the be...Exchanging gifts at the holidays is a tradition that dates back to thousands of years ago.Children are typically excused from buying gifts because they cost money kids may not have.But the truth is that some of the best gifts don't cost anything.If you would like to give meaningful gifts to family or friends at the holidays—without having to spend money—here's how you can get started.展开更多
Even when kids dont realize it,teachers listen with their ears and their hearts.So many teachers dedi-cate their lives to education and helping us raise good kids.Some of them go so far above and beyond the call of du...Even when kids dont realize it,teachers listen with their ears and their hearts.So many teachers dedi-cate their lives to education and helping us raise good kids.Some of them go so far above and beyond the call of duty that it makes you wonder if they are really angels in disguise.Stacy Caldwell is one of those teachers.展开更多
Dunhuang UNESCO Global Geopark Nestled in northwest China’s Gansu Province,Dunhuang UNESCO Global Geopark is a mesmerising fusion of extraordinary geological formations,rich history,and breathtaking desert landscapes...Dunhuang UNESCO Global Geopark Nestled in northwest China’s Gansu Province,Dunhuang UNESCO Global Geopark is a mesmerising fusion of extraordinary geological formations,rich history,and breathtaking desert landscapes.Spanning 2,180.75 square km,the geopark encompasses iconic sites such as the Yardang landforms,Mingsha Mountain(Singing Sand Dunes),and Crescent Spring,alongside cultural treasures like the Mogao Grottoes and various ancient Silk Road relics.展开更多
研究所用60个家系的吉富品系尼罗罗非鱼(GIFT strain Nile tilapia,Oreochromis niloticus;简称吉富罗非鱼)样本均为由世界渔业中心所在地马来西亚引进的原种。采用传统形态学测量方法,测量每尾鱼的体质量、体长、体高、体宽、头长、尾...研究所用60个家系的吉富品系尼罗罗非鱼(GIFT strain Nile tilapia,Oreochromis niloticus;简称吉富罗非鱼)样本均为由世界渔业中心所在地马来西亚引进的原种。采用传统形态学测量方法,测量每尾鱼的体质量、体长、体高、体宽、头长、尾柄长和尾柄高后进行主成分分析和相关分析,研究吉富品系尼罗罗非鱼群体内的形态差异。结果显示,吉富罗非鱼体高与体质量的相关性最大(R2=0.9002)。在体长与体质量对应的点状分布中,总群体、雌雄群体和每个家系群体中均呈现出2条带状,分布于2条带的个体间质量差异不显著(P>0.05),对应的个体数量之比接近常数0.7;体高、体宽、头长、尾柄长和尾柄高相应的分布则呈现出变异幅度迥异的条带。本研究表明,吉富罗非鱼群体内部在形态上存在差异。展开更多
The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new...The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety has been extended in most of areas of China. The management of genetically improved strains, including the genetic markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S304624 bp and S36568 bp were identified. The strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains worldwide. The frequency of SCAR marker Ⅰ （553 bp） was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain. The frequency of SCAR marker Ⅱ （558 bp） was 91.4% in NEW GIFT Nile tilapia, but 0% 70% in the 7 other strains. In order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt, resulted the frequency of SCAR Ⅰ and Ⅱ was 10% and 70%, respectively, much lower than that of New GIFT strain. The increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the quantitative trait loci （QTL） underlining the performance traits by long term selection, and indicate the bright potential of SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically improved strain and other strains.展开更多
Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females f...Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection展开更多
用投喂添加色素的膨化颗粒饲料和观测排便相结合的方法,研究吉富品系尼罗罗非鱼(Genetic Improvement of Farmed Tilapias;GIFT)的摄食节律。结果发现,6个家系的吉富品系尼罗罗非鱼摄食具有明显的节律性,家系之间的摄食周期存在非常显...用投喂添加色素的膨化颗粒饲料和观测排便相结合的方法,研究吉富品系尼罗罗非鱼(Genetic Improvement of Farmed Tilapias;GIFT)的摄食节律。结果发现,6个家系的吉富品系尼罗罗非鱼摄食具有明显的节律性,家系之间的摄食周期存在非常显著差异(P<0.0001);t检验发现,各家系内摄食周期和排便周期的差异均不显著(P≥0.1097)。回归分析发现,摄食周期对生长无显著的影响(P=0.8988),但与摄食量之间存在显著的线性关系(R2=0.9679,P=0.0004)。对摄食节律聚类分析,6个家系可分为(1、2、6)、(3、4)、5共3个家系类别。该项研究能为GIFT的养殖投饵和进一步选育提供理论依据,为鱼类摄食节律研究提供方法上的参考。展开更多
文摘Exchanging gifts at the holidays is a tradition that dates back to thousands of years ago.Children are typically excused from buying gifts because they cost money kids may not have.But the truth is that some of the best gifts don't cost anything.If you would like to give meaningful gifts to family or friends at the holidays—without having to spend money—here's how you can get started.
文摘Even when kids dont realize it,teachers listen with their ears and their hearts.So many teachers dedi-cate their lives to education and helping us raise good kids.Some of them go so far above and beyond the call of duty that it makes you wonder if they are really angels in disguise.Stacy Caldwell is one of those teachers.
文摘Dunhuang UNESCO Global Geopark Nestled in northwest China’s Gansu Province,Dunhuang UNESCO Global Geopark is a mesmerising fusion of extraordinary geological formations,rich history,and breathtaking desert landscapes.Spanning 2,180.75 square km,the geopark encompasses iconic sites such as the Yardang landforms,Mingsha Mountain(Singing Sand Dunes),and Crescent Spring,alongside cultural treasures like the Mogao Grottoes and various ancient Silk Road relics.
文摘研究所用60个家系的吉富品系尼罗罗非鱼(GIFT strain Nile tilapia,Oreochromis niloticus;简称吉富罗非鱼)样本均为由世界渔业中心所在地马来西亚引进的原种。采用传统形态学测量方法,测量每尾鱼的体质量、体长、体高、体宽、头长、尾柄长和尾柄高后进行主成分分析和相关分析,研究吉富品系尼罗罗非鱼群体内的形态差异。结果显示,吉富罗非鱼体高与体质量的相关性最大(R2=0.9002)。在体长与体质量对应的点状分布中,总群体、雌雄群体和每个家系群体中均呈现出2条带状,分布于2条带的个体间质量差异不显著(P>0.05),对应的个体数量之比接近常数0.7;体高、体宽、头长、尾柄长和尾柄高相应的分布则呈现出变异幅度迥异的条带。本研究表明,吉富罗非鱼群体内部在形态上存在差异。
基金National Tilapia Industry Technical System(nycytx-48-3)National Tilapia Seed Program(nyhyzx07-044-01)
文摘The NEW GIFT Nile tilapia （Oreochromis niloticus niloticus L.） is a nationally certificated new strain selected over 14 years and 9 generations from the base strain of GIFT Nile tilapia, introduced in 1994. This new variety has been extended in most of areas of China. The management of genetically improved strains, including the genetic markers for identification is needed urgently. RAPD analysis was conducted and their conversion to SCAR markers was developed. From NEW GIFT Nile tilapia, two strain-specific RAPD bands, S304624 bp and S36568 bp were identified. The strain-specific RAPD bands were gel-purified, cloned, and sequenced. Locus-specific primers were then designed to amplify the strain-specific bands. PCR amplification was conducted to test the variations in allele frequencies of two converted SCAR markers among the NEW GIFT Nile tilapia and its base strains, as well as 7 additional farmed strains worldwide. The frequency of SCAR marker Ⅰ （553 bp） was 85.7% in NEW GIFT Nile tilapia, but 16.7% in the base strain. The frequency of SCAR marker Ⅱ （558 bp） was 91.4% in NEW GIFT Nile tilapia, but 0% 70% in the 7 other strains. In order to confirm the utility of these two markers, an examination was conducted for a wild population from Egypt, resulted the frequency of SCAR Ⅰ and Ⅱ was 10% and 70%, respectively, much lower than that of New GIFT strain. The increase in allele frequency of these two SCAR markers suggests that these markers might be genetically linked to the quantitative trait loci （QTL） underlining the performance traits by long term selection, and indicate the bright potential of SCAR marker technology for tracking generations during selection progress and for distinguishing among genetically improved strain and other strains.
文摘Males of the nursery web spider Pisaura mirabil usually offer an insect prey wrapped in white silk as a nuptial gift to facilitate copulation. Males exploit female foraging preferences in a sexual context as females feed on the gift during copula- tion. It is possible for males to copulate without a gift, however strong female preference for the gift leads to dramatically higher mating success for gift-giving males. Females are polyandrous, and gift-giving males achieve higher mating success, longer copulations, and increased sperm transfer that confer advantages in sperm competition. Intriguingly, field studies show that ap- proximately one third of males carry a worthless gift consisting of dry and empty insect exoskeletons or plant fragments wrapped in white silk. Silk wrapping disguises gift content and females are able to disclose gift content only after accepting and feeding on the gift, meanwhile males succeed in transferring sperm. The evolution of deceit by worthless gift donation may be favoured by strong intra-sexual competition and costs of gift-construction including prey capture, lost foraging opportunities and investment in silk wrapping. Females that receive empty worthless gifts terminate copulation sooner, which reduces sperm transfer and likely disadvantages males in sperm competition. The gift-giving trait may thus become a target of sexually antagonistic co-evolution, where deceit by worthless gifts leads to female resistance to the trait. We discuss factors such as female mating rate and intensity of sperm competition that may shape the evolution of male deception, and how ecological factors may influence the evolution and maintenance of worthless gifts as an evolutionarily stable alternative mating strategy by frequency dependent selection
文摘用投喂添加色素的膨化颗粒饲料和观测排便相结合的方法,研究吉富品系尼罗罗非鱼(Genetic Improvement of Farmed Tilapias;GIFT)的摄食节律。结果发现,6个家系的吉富品系尼罗罗非鱼摄食具有明显的节律性,家系之间的摄食周期存在非常显著差异(P<0.0001);t检验发现,各家系内摄食周期和排便周期的差异均不显著(P≥0.1097)。回归分析发现,摄食周期对生长无显著的影响(P=0.8988),但与摄食量之间存在显著的线性关系(R2=0.9679,P=0.0004)。对摄食节律聚类分析,6个家系可分为(1、2、6)、(3、4)、5共3个家系类别。该项研究能为GIFT的养殖投饵和进一步选育提供理论依据,为鱼类摄食节律研究提供方法上的参考。
