熊野藻属Kumanoa系统分类研究进展

熊野藻属(Kumanoa)是淡水红藻中基于rbcL和SSU基因序列建立的一个属,并进一步得到了cox1和UPA序列结果的支持,隶属于串珠藻目(Batrachospermales)。本文综述了熊野藻属系统分类及我国该属植物研究的研究进展,对其主要形态特征进行了界定。该属植物与串珠藻属植物形态结构相似,但果孢子体通常半球形,位于轮节中央,受精丝长度有限,果胞枝弯曲、扭曲或螺旋状,其细胞形状明显区别于营养细胞。分子数据显示其单独聚为一支,明显区别于串珠藻属的类群。中国淡水熊野藻属已记录的种类有10种。利用分子生物学手段对我国淡水熊野藻属进行深入系统的、多特征的分类研究是今后该属植物的主要研究方向。     

弯枝藻目Compsopogonales系统分类研究进展

弯枝藻目Compsopogonales是淡水红藻中一个比较重要的类群,主要特征是:藻体分枝丝状,有匍匐和直立丝体的分化,幼体单列细胞,成熟时单列轴细胞外有皮层细胞包被,一般以单孢子繁殖。本文综述了弯枝藻目系统分类、繁殖方式及我国该目植物区系分类的研究进展。目前,该目已报道过的分类单位有2科,4属,30多个种,但其系统分类方面仍存疑甚多。中国迄今已报道的该目植物只有6种。根据目前发展趋势,利用分子生物学手段对我国该目植物进行深入系统的、多特征的分类研究是今后的主要方向。     

黄群藻目分类系统述评及主要分类特征的评价

黄群藻目Synurales是主要根据光合色素和亚显微结构特征建立的一个目,也是淡水金藻中较大的一个目,包括约160种。该目的植物体为自由运动的单细胞或群体,细胞的表质上覆盖许多硅质的鳞片,以覆瓦状、甲胄状排列或自由附着于表质上,鳞片具刺毛或无,具1条或2条不等长鞭毛。黄群藻目植物区别于其它金藻植物的主要特征为,它们的色素体仅含有叶绿素C1,鞭毛基部平行排列,并且形成硅质鳞片的硅质沉积孢囊与叶绿体外膜相连。自建立至今,该目的分类系统几经变化。本文综述了黄群藻目分类系统的研究进展,并对其主要形态特征的分类价值进行了分析。     

串珠藻科分类系统述评及主要分类特征的评价

串珠藻科Batrachospermaceae是淡水红藻中最大的一个科,包括约120种。自建立至今,该科的分类系统几经变化。本文综述了串珠藻科分类系统的研究进展,并对主要形态特征的分类价值进行了分析。     

中国淡水金藻门植物研究进展

金藻门植物是根据色素体呈黄绿色、橙黄色或黄褐色而得名的。由于金藻门植物体较小而脆弱，采集、鉴定、培养都很困难，对其的研究较有难度。本文对中国淡水金藻门植物的研究进展进行了综述。迄今，中国已报道的淡水金藻门植物有128种（包括变种、变型），研究区域主要集中于我国的华南、西南和东南的部分省市。由于金藻门植物有着特殊的生活环境，因而一些种类可以作为生态环境指示种。同时，本文还介绍了淡水金藻门植物的形态特征、分类系统、保存鉴定方法和生态环境。     

藻类制氢的研究进展和应用前景

氢气作为可再生能源正日益受到现代社会的重视,从发展清洁能源的角度来看,氢气是最理想的载能体.本文介绍了目前国内外藻类制氢各个方面的研究进展和成果,主要从产氢藻的种类、藻类产氢机制及相关酶、藻类产氢在生化和分子方面的研究进行了详尽的综述.并对藻类制氢在未来的发展和研究方向进行了分析和展望.     

微生物细胞溶胶-凝胶法磁性化研究

以微生物细胞为模板可制备具有多样形状的磁性或导电微颗粒．本文探讨微生物细胞溶胶一凝胶法磁性化的可行性,以尺寸在微米级的具有天然螺旋形体的微生物材料螺旋藻的细胞为模板进行细胞溶胶．凝胶法包覆磁性材料铁氧体的工艺研究,并通过光学显微镜、扫描电镜、电子能谱、透射电镜、X射线衍射对其细胞形态、表层成分、相结构进行观察与分析．结果表明,螺旋藻细胞经溶胶．凝胶处理后表面能包覆上铁氧体材料;其天然螺旋形体可保持良好,得到的单体表面磁性层厚度、成分基本均匀,在文中试验条件下,细胞表层铁氧体为立方尖晶石结构的Fe3O4;还可观察到细胞内部有纳米颗粒产生,同时细胞间横壁也有沉积．还探讨了微生物细胞溶胶．凝胶法磁性化工艺过程的物理化学反应机理．     

益阳地区遥感土地利用分类的波段组合效应分析

波段组合对监督分类的运算效率和分类结果有着显著影响。本文以湖南益阳TM影像为实验数据,通过波段光谱特征统计分析、叠合光谱图分析,对该地区土地利用分类波段进行了初步选取;按照3波段组合方式进行分类,并对分类效应进行了比较分析。结果表明,耕地和草地难区分、未利用土地易错分为建设用地是共同问题;TM2、3、4组合能够较好地区分耕地和草地,同时对林地和草地的区分效果也最好,分类总精度最高;TM2、3、5组合对未利用土地的识别能力相对最高;TM2、3、7组合,TM2、4、7组合以及TM2、5、7组合对水体的分类效果最好。本研究对数据降维、资料不足时最大限度发挥资料可用性、针对特别应用目的进行传感器波段设计具有一定的参考价值。     

连续采煤机工作面硬质包裹体分布的模拟研究

短壁工作面上硬质包裹体的分布直接影响连续采煤机的截割阻力、机器振动、工作噪音和截割的经济效益。文章在假定包裹体的几何形状为旋转椭球体的情况下,对长轴尺寸服从均匀分布、正态分布、指数分布、威布尔分布、伽玛分布和贝塔分布下的硬质包裹体在煤层中的分布进行了计算机模拟,并分析了各种情况的特征,为了解连续采煤机工作面硬质包裹体的分布、研究其截割过程和机器的工作性能创造了条件。     

翼身融合航行体操纵特性研究

翼身融合航行体以其独特的外形特征和机动性能成为未来海洋发展的重要方向,而人们对这一类型的航行体操纵特点并不了解.本文采用基于半相对坐标系的数值模拟方法对新型航行体操纵特性进行研究,并且通过量纲分析对主要影响参数进行分析.发现水平面回转时给定航速条件下,航行体尾部漩涡会随着旋转半径的变化出现偏转现象,进一步的数值模拟结果表明:旋转半径越小,左右漩涡的不对称性会越明显.当旋转半径给定时,不同航速条件下,航行体尾涡的左右分离位置基本一致.对比发现该类航行体的垂直面回转操纵性要优于水平面回转操纵性,即这类航行体在改变航行深度机动方面具有更大优势.     

Sexual reproduction in the Candida clade: cryptic cycles, diverse mechanisms, and alternative functions

To have sex, or not to have sex, is a question posed by many microorganisms. In favor of a sexual lifestyle is the associated rearrangement of genetic material that confers potential fitness advantages, including resistance to antimicrobial agents. The asexual lifestyle also has benefits, as it preserves complex combinations of genes that may be optimal for pathogenesis. For this reason, it was thought that several pathogenic fungi favored strictly asexual modes of reproduction. Recent approaches using genome sequencing, population analysis, and experimental techniques have now revised this simplistic picture. It is now apparent that many pathogenic fungi have retained the ability to undergo sexual reproduction, although reproduction is primarily clonal in origin. In this review, we highlight the current understanding of sexual programs in the Candida clade of species. We also examine evidence that sexual-related processes can be used for functions in addition to mating and recombination in these organisms.     

药用植物羌活现状及其民族植物学调查

羌活为重要的传统中药和藏药常用药材，大量的汉藏药方和成药均作为重要的配伍药材加以使用。羌活传统产区主要是藏族、羌族和其它少数民族的聚居的高寒山区，经济较为落后，交通不便。由于难以驯化栽培，药材来源主要依赖野生资源采挖，但由于受到种子发育不完全、后熟期长等本身繁殖特性的限制，羌活繁殖和种群恢复主要是通过无性繁殖实现，野生资源恢复受到严重制约。道地产区的调查发现，羌活野生生境正受到前所未有的破坏，包括生境丧失、破碎化、土壤退化、土地利用模式改变和环境变化等；调查还发现近年来羌活药材价格与采挖量之间的关系，以及当地民族植物学方面的状况。羌活野生资源的破坏受到利益驱使、致使采挖时间和方式等利用模式发生改变，极不利于羌活野生资源的保存和种群恢复，若不规范羌活野生资源的利用和引种驯化，进行人工栽培，羌活野生资源不但难以实现可持续利用，而且还将遭到毁灭性破坏，并有灭绝的危险。本文最后提出了药用羌活属植物的保护性开发和可持续利用可能途径。     

Evolutionary and ecological consequences of interspecific hybridization in cladocerans

The evolutionary process of interspecific hybridization in cladocerans is reviewed based on ecological and population genetic data. The evolutionary consequences of hybridization, biogeographic patterns and fitness comparisons are analyzed within the conceptual framework of theories on hybridization. Among species of theD. longispina complex no interpopulational transition zones (hybrid zones) have been detected, but rather patchy distributions of hybrids and parentals have been found. Hybrids occur across broad geographic ranges and can be more abundant than parental species. Due to asexual reproduction (ameiotic parthenogenesis), hybrid breakdown can be avoided, and hybrids can even (temporarily) combine advantageous traits of both parental species. Evolutionary consequences may arise from repeated backcrossing, which in some cases results in introgression and patterns of reticulate evolution.Those forms which possess in some considerable degree the character of species, but which are so closely similar to some other forms, or are so closely linked to them by intermediate gradations, that naturalists do not like to rank them as distinct species, are in several respects the most important to us (Charles Robert Darwin 1859)     

Evolution and ecological correlates of uniparental reproduction in freshwater snails

We review the spatial and temporal correlates of uniparental reproduction in freshwater snails as they pertain to the ecological hypotheses for the maintenance of biparental sex. The biogeographic evidence from two species (Potamopyrgus antipodarum andBulinus truncatus) presently supports the Red Queen hypothesis that biparental reproduction is selected as a way to reduce the risk to progeny of parasite attack. Uniparental reproduction in these species is associated with low levels of infection by parasites (castrating digenetic trematodes), suggesting that parthenogenesis or self-fertilization can replace cross-fertilization when the risk of infection is low. In addition, inB. truncatus, the opportunity for cross-fertilization coincides with the season in which parasite attack is highest. In a third species (Campeloma decisum), parthenogenetic reproduction is correlated with latitude and the presence of a non-castrating trematode that may prevent cross-fertilization; these patterns suggest that parthenogenesis has been selected as a mechanism to assure reproduction. Finally, we discuss the spotty taxonomic distribution of parthenogenetic species.     

Asexual reproduction: Genetics and evolutionary aspects

Reproduction is essential to all organisms if they are to contribute to the next generation. There are various means and ways of achieving this goal. This review focuses on the role of asexual reproduction for eukaryotic organisms and how its integration in a life cycle can influence their population genetics and evolution. An important question for evolutionary biologists as to why some organisms reproduce sexually, as opposed to asexually, is addressed. We also discuss the economic and medical importance of asexual organisms. Received 4 December 2006; received after revision 25 January 2007; accepted 20 February 2007     

Melatonin: presence and formation in invertebrates

In vertebrates, it is now clearly demonstrated that the pineal gland is implicated in conveying photoperiodic information via the daily pattern of melatonin secretion. Invertebrates, like vertebrates, use photoperiodic changes as a temporal cue to initiate physiological processes such as reproduction or diapause. How this information is integrated in invertebrates remains an unsolved question. Our review will be an attempt to evaluate the possible role of melatonin in conveying photoperiodic information in invertebrates. It is now well demonstrated in both vertebrates and invertebrates that melatonin as well as its precursors or synthesizing enzymes are present in various organs implicated in photoreceptive processes or in circadian pacemaking. Melatonin, serotonin or N-acetyltransferase have been found in the head, the eyes, the optic lobe and the brain of various invertebrate species. In some species it has also been shown that melatonin is produced rhythmically with high concentrations reached during the dark period. Moreover, the physiological effects of melatonin on various periodic processes such as rhythmic contractions in coelenterates, fissioning of asexual planarians or reproductive events in flies have been reported in the literature. All these results support the hypothesis (refs 36, 37) that melatonin is not solely a pineal hormone but that it may be an evolutionary conservative molecule principally involved in the transduction of photoperiodic information in all living organisms.     

Intrinsic links among sex,emotion, and reproduction

Species survival is dependent on successful reproduction. This begins with a desire to mate, followed by selection of a partner, copulation and in monogamous mammals including humans, requires emotions and behaviours necessary to maintain partner bonds for the benefit of rearing young. Hormones are integral to all of these stages and not only mediate physiological and endocrine processes involved in reproduction, but also act as neuromodulators within limbic brain centres to facilitate the expression of innate emotions and behaviours required for reproduction. A significant body of work is unravelling the roles of several key hormones in the modulation of mood states and sexual behaviours; however, a full understanding of the integration of these intrinsic links among sexual and emotional brain circuits still eludes us. This review summarises the evidence to date and postulates future directions to identify potential psycho-neuroendocrine frameworks linking sexual and emotional brain processes with reproduction.     

AfricanClarias catfish elicits long-lasting weak electric pulses

The African catfishClarias is generally considered to possess electroreceptors but not electric organs. It is reported here that at least one species of the genus,C. gariepinus, can produce weak monophasic discharges during aggressive interactions with conspecifics. These irregular pulse discharges are substantially longer than the electric organ discharges (EODs) of all other pulse-generating freshwater electric fishes. It is also shown that the optimal sensitivity ofClarias' ampullary receptors just corresponds to the modal pulse duration. TheClarias catfish, with its very specific EOD, may be of special interest in the evolution of the electrogenic system in the siluriforms, comprising many electroreceptive but nonelectrogenic catfish species.     

Muscular and nervous systems of the cubopolyp (Cnidaria)

Summary New observations on the morphology, anatomy, asexual reproduction and metamorphosis of the formerly unknown polyp of the tropical Cubomedusae resulted in the conclusion that a new class Cubozoa must be established and positioned between the Scyphozoa and Hydrozoa. This conclusion could be confirmed by the histological investigation of the cubopolyp's muscular and nervous systems by light and transmission electron microscopy.