两栖动物的染色体及其演化

脊椎动物从水生进化到陆生的过程中,两栖动物有着“承先启后”的重要作用。两栖动物能在陆地存活,但无陆地繁殖的本领。是一群过渡类群。“二者兼而有之”的过渡性质,不仅表现在形态、生态和生理机能上,而且还反映在遗传物质-DNA-的携带者-染色体的特征上。60年代后,两栖动物的核型研究有了长足的发     

四川察青松多自然保护区的两栖动物

四川察青松多自然保护区共有两栖动物5种,区系组成以喜马拉雅－横断山区特有种属为主,位点选择和繁殖习性的多样性降低了不同物种间对繁殖微生境的竞争。     

人工养殖两栖动物的方法初探

栖息地的减缩和破坏是野生动物种群衰退重要因素之一,尤对那些小型且不为人们注意、目前仍属非经济动物种类,其栖息地的减缩和破坏更是最重要原因。对这种现象,有识之士都在大声疾呼：保护生物多样性,保护人类赖以生存的地球。近年来国外对动物园的功能提出了许多新的...     

鱼类的繁殖类型

鱼类与高等脊椎动物相比其繁殖方式具有多样性,不仅有卵生、胎生和卵胎生,还有孤雌生殖、雌核发育和杂合发育。     

两栖动物线粒体基因组结构特征分析

对2007年6月13日以前公布于GenBank上的78种两栖动物的线粒体基因组全序列进行了总结、比较和分析。78种基因组中基因的数量从35~41个不等;根据基因的数量、种类及其排列顺序的差别将其分为22种基因组类型,其进而聚为3组,其中类型4为两栖纲与其它脊椎动物的常见类型,类型8为两栖纲中现生3个目的公有类型。与类型4比较,其余21种线粒体基因组类型涉及基因变动的基因共有18个,其中变动比较多的是tRNA基因,移位、增多和缺失的发生频率都较大,而蛋白编码基因比较稳定,主要是移位。78种两栖动物中,蚓螈目的线粒体基因组均小于18000bps,多数在15000~16000bps;有尾目和无尾目均大于16000bps,其中有尾目多数在16000~17000bps,无尾目的多数在17000~18000bps。     

海南部分地区两栖动物的调查

于2005年2月至3月调查r海南岛的部分地区两栖动物,主要集中在戈枕、湾岭和吊罗山,共计采集到13种标本,分隶4科7属。     

热河生物群的两栖动物

两栖类是脊椎动物从水生到陆生的过渡类群。由于种种原因 ,两栖动物化石 ,尤其是对于研究现代两栖类起源和演化具有重要意义的中生代两栖类化石 ,以往非常罕见。近年来 ,在冀北和辽西的中生代地层中发现了大量保存精美的两栖类化石 ,我国学者对它们的研究已经引起了国际学术界的关注。“三燕丽蟾”、“葛氏辽蟾”、“东方塘螈”和“钟健辽西螈”等新属种是我国第一批中生代滑体两栖类化石 ,为研究现代两栖动物的早期进化和迁徙提供了重要信息。现代两栖动物的正式名称叫“滑体两栖动物(英文名Ｌｉｓｓａｍｐｈｉｂｉａｎｓ)”。滑体两栖动物…     

刘承钊教授生前发表的两栖动物新种

本文介绍刘承钊教授生前本人或与合作者描述发表的两栖动物66个新种,分隶2目9科,计有尾目2科9种,无尾目7科57种(名单见附表)。其中,刘承钊和胡淑琴(1961)《中国无尾两栖类》将以下4种列为同物异名:108页:ＡｅｌｕｒｏｐｈｒｙｎｅｂｒｅｖｉｐｅｓＬｉｕ=胸腺猫眼蟾ＡｇｌａｎｄｕｌａｔｕｓＬｉｕ[后改属名,称为胸腺齿突蟾Ｓｃｕｔｉｇｅｒｇｌａｎｄｕｌａｔｕｓ(Ｌｉｕ)]。265页:胡氏树蛙ＲｈａｃｏｐｈｏｒｕｓｈｕｉＬｉｕ=杜氏树蛙ＲｈａｃｏｐｈｏｒｕｓｄｕｇｒｉｔｅｉＤａｖｉｄ[后改属名,称为杜氏泛树蛙Ｐｏｌｙｐｅｄａｔｅｓｄ…     

九龙山两栖动物初步调查报告

1983—1985年,浙江丽水地区科委、丽水地区生物学会下达了两栖类动物资源调查课题时,笔者在浙江九龙山自然保护区从海拔260—1300米以上的不同采集点进行了两栖类的采集和调查。共采得标本300多号,结合文献资料,已知九龙山两栖动物有2目8科11属26种。比以往报道增加了6种。同时在考察中发现了一个新种——九龙棘蛙,并对崇安髭蟾及中华大蟾蜍的繁殖习性进行了生态观察。     

中国两栖动物染色体研究名录

根据20余年资料,对中国无足、有尾和无尾类两栖动物的染色体研究进行了整理总结。     

Reproductive capacity and mode of death of yeast cells

The technique of micromanipulation was used to observe the number of daughter cells produced by individual cells of two yeasts, one a brewing strain and the other a hexaploid hybrid. The mode in which these cells died was also recorded. An average reproductive capacity of 34 daughter cells was found for the brewing yeast and of 17 daughter cells for the hexaploid strain. Two distinct modes of death were observed, one in which the final daughter cell appeared normal and the other where the last daughter cell could not be detached from its mother and both cells died. A correlation was obtained between the mode of death of a cell and its reproductive capacity. A number of final daughter cells (the 28th - 46th buds of their mother cell) was also observed through a considerable number of divisions and these cells were found apparently normal in their reproductive ability. It is suggested that cessation of budding is a consequence of reduction of the active surface to volume ratio because of the lower metabolic activity of scar tissue.     

Reproductive mode and speciation: the viviparity-driven conflict hypothesis

In birds and frogs, species pairs retain the capacity to produce viable hybrids for tens of millions of years, an order of magnitude longer than mammals. What accounts for these differences in relative rates of pre- and postzygotic isolation? We propose that reproductive mode is a critically important but previously overlooked factor in the speciation process. Viviparity creates a post-fertilization arena for genomic conflicts absent in egg-laying species. With viviparity, conflict can arise between: mothers and embryos; sibling embryos in the womb, and maternal and paternal genomes within individual embryos. Such intra- and intergenomic conflicts result in perpetual antagonistic coevolution, thereby accelerating interpopulation postzygotic isolation. In addition, by generating intrapopulation genetic incompatibility, viviparity-driven conflict favors polyandry and limits the potential for precopulatory divergence. Mammalian diversification is characterized by rapid evolution of incompatible feto-maternal interactions, asymmetrical postzygotic isolation, disproportionate effects of genomically-imprinted genes, and "F(2) hybrid enhancement. " The viviparity-driven conflict hypothesis provides a parsimonious explanation for these patterns in mammalian evolution.     

Reproductive mode in the percomorph fish genus Polyprion Oken

Reproductive mode of the two widespread species Polyprion americanus (Bloch and Schneider, 1801) and P. oxygeneios (Schneider in Bloch and Schneider, 1801) was investigated in specimens from New Zealand waters. Analysis of sex ratios, length frequencies and gonad morphology indicates that both species are primary gonochorists. Published suggestions that Polyprion species are hermaphroditic and undergo sex change are rejected.     

Parasites of British Amphibians

Algal bioassays employing the test alga Selenastrum capricornutum Printz. are a relatively simple and reliable method of studying the effects of aquatic pollutants on plant growth in natural and waste waters. Details of algal bioassays based upon Liebig's ‘Law of the Minimum’ are described to enable students in schools and universities to assess the relative potential fertility of freshwater bodies, to evaluate the growth-promoting effects of nitrates and phosphates, to identify growth-limiting nutrients, and to determine the growth-inhibiting effects of toxic pollutants. Examples taken from students' investigations of Welsh river waters are cited in support.     

Immunological Tolerance in Amphibians

SYNOPSIS. A state of immunological tolerance, or specific unresponsivenessto foreign antigen, can be induced in amphibians by joiningtwo nonsibling embryos in parabiotic union. The induced toleranceis immunologically specific; the co-partners are tolerant ofeach other' santigens but do respond to unrelated antigens fromthird parties. The parabionts are blood-cell chimeras; eachcontains blood elements of the type proper to the other. Thedegree of chimerism wanes in the later life of the parabionts,which may be the consequence of the appearance of a new cloneof uninhibited reactive cells derived from the bone marrow. Tolerance to a particular antigen is interpreted as arisingby the deletion of the population of competent lymphocytes capableof responding to that antigen. The breakdown of tolerance occursthrough the emergence of a new population of antigen-reactivecells. In essence, a tolerant cell as a discrete entity doesnot exist.     

Reproductive mode and life cycle of the ash dieback pathogen Hymenoscyphus pseudoalbidus

Ash dieback caused by the fungal pathogen Hymenoscyphus pseudoalbidus is currently ravaging in Europe, killing Fraxinus excelsior and Fraxinus angustifolia trees of all age classes. The aim of this work was to elucidate aspects of the reproduction biology of this fungal pathogen and its cryptic, non-pathogenic sister species Hymenoscyphus albidus. The mating type (MAT) locus of both species was identified, partly sequenced and characterized. Whereas a heterothallic MAT organization was detected in H. pseudoalbidus, H. albidus was shown to be structurally homothallic. The molecular MAT determination of H. pseudoalbidus was confirmed by crossing experiments on sterile ash petioles. Crossings of strains exhibiting alternate MAT idiomorphs produced fertile apothecia whereas crosses of strains with identical MAT idiomorphs were never successful. Offspring genotyping with microsatellites (MSs) and the MAT marker confirmed that both parental strains were involved in apothecia formation. In addition, polymorphic MS were shown to follow Mendelian inheritance. However, for yet unknown reasons the MAT ratio of progenies of one successful cross revealed a significant segregation distortion. Based on the MAT sequences of H. pseudoalbidus a multiplex PCR was developed, allowing for a quick and reliable MAT determination. The PCR was applied to screen the MAT ratio of two H. pseudoalbidus populations derived from the country of the disease outbreak in Poland and two populations from the disease periphery in Switzerland. None of the screened populations showed a significant deviation from the 1:1 ratio, expected under random mating. Therefore, an initial clonal distribution through asexually produced conidiospores as observed for other fungal pathogens holds not true for H. pseudoalbidus. Instead, our data is highly supportive for a distribution through ascospores. Leaf petioles collected in the field were thoroughly analyzed for the number of different colonizing strains and their mating behavior. Up to eight different H. pseudoalbidus genotypes were found on a single petiole. Cross-fertilizations of strains on the same petiole and fertilizations of unknown strains from outside were found, indicating that fertilization is mediated by spermatia. The presented study complements our understanding of the life cycle of this highly destructive pathogen. The possibility to perform sexual crosses in the lab provides ample opportunities for further genetic studies of H. pseudoalbidus and related species in the future.     

陕西周至老县城自然保护区两栖动物多样性调查

于2003年7月～8月和2004年5月对陕西周至老县城自然保护区进行两次实地考察,结合有关文献资料的报道结果,该地区有两栖动物8种,归隶2目、5科、8属,其中1种为未定种Scutiger sp.,与宁陕齿突蟾Scutiger ningshanensis相似,其代表的属和科在邻近的5个自然保护区目前均无发现与报道;与邻近的5个自然保护区的物种分布相似性比较表明,老县城自然保护区在两栖动物分布上与周至自然保护区更相近.