Maturation trends indicative of rapid evolution preceded the collapse of northern cod

Northern cod, comprising populations of Atlantic cod (Gadus morhua) off southern Labrador and eastern Newfoundland, supported major fisheries for hundreds of years. But in the late 1980s and early 1990s, northern cod underwent one of the worst collapses in the history of fisheries. The Canadian government closed the directed fishing for northern cod in July 1992, but even after a decade-long offshore moratorium, population sizes remain historically low. Here we show that, up until the moratorium, the life history of northern cod continually shifted towards maturation at earlier ages and smaller sizes. Because confounding effects of mortality changes and growth-mediated phenotypic plasticity are accounted for in our analyses, this finding strongly suggests fisheries-induced evolution of maturation patterns in the direction predicted by theory. We propose that fisheries managers could use the method described here as a tool to provide warning signals about changes in life history before more overt evidence of population decline becomes manifest.     

Plankton effect on cod recruitment in the North Sea

The Atlantic cod (Gadus morhua L.) has been overexploited in the North Sea since the late 1960s and great concern has been expressed about the decline in cod biomass and recruitment. Here we show that, in addition to the effects of overfishing, fluctuations in plankton have resulted in long-term changes in cod recruitment in the North Sea (bottom-up control). Survival of larval cod is shown to depend on three key biological parameters of their prey: the mean size of prey, seasonal timing and abundance. We suggest a mechanism, involving the match/mismatch hypothesis, by which variability in temperature affects larval cod survival and conclude that rising temperature since the mid-1980s has modified the plankton ecosystem in a way that reduces the survival of young cod.     

Collapse and recovery of marine fishes

Overexploitation and subsequent collapse of marine fishes has focused attention on the ability of affected populations to recover to former abundance levels and on the degree to which their persistence is threatened by extinction. Although potential for recovery has been assessed indirectly, actual changes in population size following long-term declines have not been examined empirically. Here I show that there is very little evidence for rapid recovery from prolonged declines, in contrast to the perception that marine fishes are highly resilient to large population reductions. With the possible exception of herring and related species that mature early in life and are fished with highly selective equipment, my analysis of 90 stocks reveals that many gadids (for example, cod, haddock) and other non-clupeids (for example, flatfishes) have experienced little, if any, recovery as much as 15 years after 45-99% reductions in reproductive biomass. Although the effects of overfishing on single species may generally be reversible, the actual time required for recovery appears to be considerable. To exempt marine fishes from existing criteria used to assign extinction risk would be inconsistent with precautionary approaches to fisheries management and the conservation of marine biodiversity.     

The genome sequence of Atlantic cod reveals a unique immune system

Atlantic cod (Gadus morhua) is a large, cold-adapted teleost that sustains long-standing commercial fisheries and incipient aquaculture. Here we present the genome sequence of Atlantic cod, showing evidence for complex thermal adaptations in its haemoglobin gene cluster and an unusual immune architecture compared to other sequenced vertebrates. The genome assembly was obtained exclusively by 454 sequencing of shotgun and paired-end libraries, and automated annotation identified 22,154 genes. The major histocompatibility complex (MHC)?II is a conserved feature of the adaptive immune system of jawed vertebrates, but we show that Atlantic cod has lost the genes for MHC?II, CD4 and invariant chain (Ii) that are essential for the function of this pathway. Nevertheless, Atlantic cod is not exceptionally susceptible to disease under natural conditions. We find a highly expanded number of MHC?I genes and a unique composition of its Toll-like receptor (TLR) families. This indicates how the Atlantic cod immune system has evolved compensatory mechanisms in both adaptive and innate immunity in the absence of MHC?II. These observations affect fundamental assumptions about the evolution of the adaptive immune system and its components in vertebrates.     

星际OH及其脉泽的一种新的发生机制

针对星际ＯＨ自由基及ＯＨ脉泽起源的多种解释各自存在的困境,抓住ＯＨ的生成环境特征,从星形成区紫外光子与Ｈ２Ｏ分子的相互作用出发,对ＯＨ自由基的产生与ＯＨ脉泽的激发机制提出一种新解释。这种新解释克服了过去提出的辐射机制的困难,并且能满足各实际天文条件,因此是一种有前途的机制。     

工程造价动态计算方法研究

本文首先提出了工程造价动态管理的含义及内客．给出了两种工程造价动态计算方法及计算公式．并分别分析了两种方法的优缺点及适用条件。     

A common somitic origin for embryonic muscle progenitors and satellite cells

In the embryo and in the adult, skeletal muscle growth is dependent on the proliferation and the differentiation of muscle progenitors present within muscle masses. Despite the importance of these progenitors, their embryonic origin is unclear. Here we use electroporation of green fluorescent protein in chick somites, video confocal microscopy analysis of cell movements, and quail-chick grafting experiments to show that the dorsal compartment of the somite, the dermomyotome, is the origin of a population of muscle progenitors that contribute to the growth of trunk muscles during embryonic and fetal life. Furthermore, long-term lineage analyses indicate that satellite cells, which are known progenitors of adult skeletal muscles, derive from the same dermomyotome cell population. We conclude that embryonic muscle progenitors and satellite cells share a common origin that can be traced back to the dermomyotome.     

Genetic history of an archaic hominin group from Denisova Cave in Siberia

Using DNA extracted from a finger bone found in Denisova Cave in southern Siberia, we have sequenced the genome of an archaic hominin to about 1.9-fold coverage. This individual is from a group that shares a common origin with Neanderthals. This population was not involved in the putative gene flow from Neanderthals into Eurasians; however, the data suggest that it contributed 4-6% of its genetic material to the genomes of present-day Melanesians. We designate this hominin population 'Denisovans' and suggest that it may have been widespread in Asia during the Late Pleistocene epoch. A tooth found in Denisova Cave carries a mitochondrial genome highly similar to that of the finger bone. This tooth shares no derived morphological features with Neanderthals or modern humans, further indicating that Denisovans have an evolutionary history distinct from Neanderthals and modern humans.     

Spatio-temporal correlations and visual signalling in a complete neuronal population

Statistical dependencies in the responses of sensory neurons govern both the amount of stimulus information conveyed and the means by which downstream neurons can extract it. Although a variety of measurements indicate the existence of such dependencies, their origin and importance for neural coding are poorly understood. Here we analyse the functional significance of correlated firing in a complete population of macaque parasol retinal ganglion cells using a model of multi-neuron spike responses. The model, with parameters fit directly to physiological data, simultaneously captures both the stimulus dependence and detailed spatio-temporal correlations in population responses, and provides two insights into the structure of the neural code. First, neural encoding at the population level is less noisy than one would expect from the variability of individual neurons: spike times are more precise, and can be predicted more accurately when the spiking of neighbouring neurons is taken into account. Second, correlations provide additional sensory information: optimal, model-based decoding that exploits the response correlation structure extracts 20% more information about the visual scene than decoding under the assumption of independence, and preserves 40% more visual information than optimal linear decoding. This model-based approach reveals the role of correlated activity in the retinal coding of visual stimuli, and provides a general framework for understanding the importance of correlated activity in populations of neurons.     

Carbon isotope composition of low molecular weight hydrocarbons and monocarboxylic acids from Murchison meteorite

The origin of the organic matter in carbonaceous meteorites remains controversial despite extensive study over the past 20 yr. Motivated by the expectation that the patterns of isotopic variation with molecular structure among the organic compounds would contain important clues to their origin, we have measured the carbon isotopic compositions for individual hydrocarbons and monocarboxylic acids from Murchison meteorite, a C2 carbonaceous chondrite which fell in Australia in 1969. With few exceptions, notably benzene, the volatile products are substantially isotopically heavier than their terrestrial counterparts, signifying their extraterrestrial origin. For both classes of compounds, the ratio of 13C to 12C decreases with increasing carbon number in a roughly parallel manner, and each carboxylic acid exhibits a higher isotopic ratio than the hydrocarbon containing the same number of carbon atoms. These trends are consistent with the kinetically controlled synthesis of higher homologues from lower ones. The results suggest the possibility that the production mechanisms for hydrocarbons and carboxylic acids may be similar; they also impose constraints on the identity of the reactant species.     

达乌尔黄鼠室内繁殖的可能影响因素

繁殖活动是种群延续的基础,也是种群生态学和行为生态学研究的一个重要部分,动物是否能够繁殖成功将影响到整个种群的生存和灭亡。按照现代生活史原理,繁殖成功率决定于环境因素、性成熟的年龄、繁殖次数、婚配制度、个体所处的社会等级地位等。物种为了提高其自身的适合度,会根据环境和自身状况等条件来调整繁殖投入,进而影响其繁殖成功率。达乌尔黄鼠（Spermophilus daurious）广泛分布于我国西北、东北和华北地区,具有冬眠的生物学特性。很多生物学工作者和医学工作者都以其为模型动物,进行研究。为了使达乌尔黄鼠在实验室内繁殖成功,并将其实验动物化,结合国内外相关文献和实验室内环境,分析了可能会影响达乌尔黄鼠室内繁殖的因素并提出适当的对策,以便为该物种的实验室繁殖提供参考。     

Evolutionary biology: adaptive developmental plasticity in snakes

The morphology of organisms is generally well matched to their environment, presumably because expression of their genes is tailored either at the population or the individual level to suit local conditions: for example, snake populations that persistently encounter large prey may accumulate gene mutations that specify a large head size, or head growth may be increased in individual snakes to meet local demands (adaptive developmental plasticity). Here we test the relative contributions of genetics and environment to the jaw sizes of two tiger snake populations: one that consumes small prey on the mainland, and an island population that relies on larger prey and has a larger jaw size. Although the idea of adaptive plasticity in response to environmental pressures is controversial, we find that both factors influence the difference in jaw size between the two populations, and the influence of developmental plasticity is greater in the island population.     

果蝇分子群体遗传研究分析方法概述

果蝇属物种长期以来被作为基础生物学、特别是群体和进化遗传学的模式物种,来探讨生物学中的一些基本问题,如物种形成的遗传机制、新基因的起源及其方式、适应性进化的遗传机制等.群体遗传的方法贯穿于遗传学、生态学、古生物学、系统发育学等领域之中,已渐成为基础生物学研究的重要方法.围绕果蝇群体遗传研究中的3个主要问题,即起源地、群体历史动态和群体遗传结构,就当前用于分析上述问题的方法进行了概述,并强调了发展适用于多个座位数据的分析方法是将来的一个重要发展方向.     

加快墨瑞鳕新兴水产养殖业发展的对策

 阐述了澳洲墨瑞鳕（Murray cod，Maccullochella peelii）的优质特性；总结了项目组近年来的研究进展与成效，通过科企联合攻关，应用水产动物育种学、养殖学等理论与技术方法，系统研究了墨瑞鳕人工繁、育、养及疾病防控等技术，并进行了工厂化规模化育苗，形成了集繁殖方法、繁养设备、饲料配制、疾病防治及养殖等关键技术的完善体系；并结合区域实际，提出了发展墨瑞鳕新兴水产养殖产业的对策。     

一种有效的单核细胞增生李氏菌检测方法

将两种稀释度（10^-4和10^-7）的单核细胞增生李氏菌液加入鳕鱼增菌液中，加入到鳕鱼增菌液的菌数为55．5个／100ml，按最可能数计数法（MPN）能检测到的菌数为110个／100ml，增菌液DFB培养48h后，能检测到的最低浓度为0．055个／ml，说明所采用的DFB、FB两级增菌，EHA、PALCAM平板分离，再结合一系列的菌株鉴定特征，是一种有效的单核细胞增生李氏菌检测方法。     

高山松不同居群种子萌发及其分化研究

高山松是云南松和油松自然杂交产生的二倍体杂种,不同居群形成的遗传背景及生境差异很大.本研究以来自该物种分布区内有代表性的8个居群为试材,在理论亲本种之一即云南松生境下比较其萌发特征.结果表明:不同居群种子萌发动态表现出明显的"S"型曲线,拟合模型检验均达极显著水平,应用Logistics方程拟合效果较好,整个萌发期可分为萌发初期、萌发快速期和萌发后期;不同居群在萌发物候和萌发数量上存在一定的差异,萌发快速期起始时间为7～9 d,结束时间为11～15 d,而快速期持续时间较稳定;不同居群萌发率为52.12%～88.94%,平均73.65%,其中萌发快速期的萌发率为33.10%～49.94%,平均42.28%,萌发快速期占整个萌发期比率较大,分别为47.14%～66.40%,平均为58.20%;居群间的分化表现为以分布区东北部紧接油松分布的MK居群萌发最早,速度最快,萌发率最高,LX次之,而NY居群萌发率最低,萌发速度最慢,其它居群介于中间.快速期萌发率与总萌发率间存在显著正相关关系,相关系数为0.772 5,拟合值与实测值呈极显著的相关关系,相关系数为0.999 5.这些结果表明,高山松在理论亲本种之一即云南松生境下也表现出正常的萌发能力,且不同居群间存在明显的分化,这与高山松的杂交起源特性及不同居群复杂的遗传背景有关.     

杨树能源林新无性系苗期生物量及热值研究

以1年生杂交杨树无性系为试验材料,在生长季结束后对茎、皮、根等器官的生物量及热值进行研究。结果表明：共有13个杨树无性系的生物量高于平均值,无性系208的地上部分、地下部分和生物量均为最高,分别达到485.77、146.18、631.95 g;不同器官间干质量热值的顺序为茎、皮、根。不同杨树无性系的单株干质量热值存在极显著差异,其变异幅度为18.659~19.141 kJ/g。选出的优良无性系单株热值、生物量和单株干质量热值平均值分别比群体平均值高26.12%、25.99%和0.12%。不同无性系单株热值的差异主要来源于生物量。     

Carbon isotope composition of individual amino acids in the Murchison meteorite

A significant portion of prebiotic organic matter on the early Earth may have been introduced by carbonaceous asteroids and comets. The distribution and stable-isotope composition of individual organic compounds in carbonaceous meteorites, which are thought to be derived from asteroidal parent bodies, may therefore provide important information concerning mechanistic pathways for prebiotic synthesis and the composition of organic matter on Earth before living systems developed. Previous studies have shown that meteorite amino acids are enriched in 13C relative to their terrestrial counterparts, but individual species were not distinguished. Here we report the 13C contents of individual amino acids in the Murchison meteorite. The amino acids are enriched in 13C, indicating an extraterrestrial origin. Alanine is not racemic, and the 13C enrichment of its D- and L-enantiomers implies that the excess of the L-enantiomer is indigenous rather than terrestrial contamination, suggesting that optically active materials were present in the early Solar System before life began.     

论艺术起源的多元合理性

艺术起源研究的多元化现象的原因：原代久远，原始艺术遗迹的发掘使原有理论被推翻，新学说层出不穷；其次，原始艺术形式的多元化特征及非兼容性导致各学说之间的必然矛盾；最根本的原因是艺术史家以其主观价值标准来阐释这一客观现象，必然造成诸多结论多元并存的现状。     

地理学视野中的上海创意产业空间集聚

创意产业又称为创意工业、创意经济,处于产业链和价值链的高端,依存于大城市迅速发展,为推动城市产业结构升级和功能转型提供了新的载体和内容．上海创意产业集聚经历了自发集聚到政府引导的发展过程,按照上海市经济委员会的行业分类,将创意产业空间集聚按照行业属性、生产过程两种方式分类．创意产业空间集聚在地理空间上存在明显的分异．