银额果蝇(Drosophila albomicans)B染色体对繁殖的影响

利用遗传背景一致的３类含有不同Ｂ染色体数目的银额果蝇（Ｄｒｏｓｏｐｈｉｌａ ａｌｂｏｍｉｃａｎｓ）品系,对繁殖的２个参数,即净繁殖量和性比进行了比较研究。结果表明Ｂ染色体对净繁殖量有着显著的影响,其影响依赖于Ｂ染色体数目的不同而不同;低数目增加其携带者的净繁殖量,而在高含量时有使其携带者净繁殖量下降的趋势。Ｂ染色体对繁殖的影响还具有一定的时间分布特征,即３类品系净繁殖量的差异主要集中在雌绳繁殖的早     

问题解答

问:苍蝇的繁殖能力有多大? 答:苍蝇的繁殖力主要决定于卵巢小管数目、世代厉期和繁殖季节的长短等因素。如果卵巢小管数目多,世代历期短即生活史短,而且当地的繁殖季节长,则繁殖能力就很高。此外营养条件、温度与湿度等对苍蝇的繁殖都有影响,其中营养的丰富与否影响最大。雌蝇卵巢的发育必须有蛋白质食物,如家蝇成虫单食蔗糖水,则卵巢不能发育;幼虫期的营养丰富或缺乏对成虫卵巢的发育也是有影响的。一般说来,卵生的蝇类,繁殖力是相当惊人的,一只雌蝇一生可产400-2000粒卵。如家蝇的卵巢小管总数多于100支,所以每批产卵在百粒     

温度对芙新姬小蜂孤雌产雌品系成虫控制斑潜蝇的潜力的影响

【目的】芙新姬小蜂Neochrysocharis formosa是潜叶蝇类害虫的优势寄生蜂。该寄生蜂具有两性生殖和孤雌产雌生殖两种繁殖模式,其孤雌产雌品系可在低密度下快速建立种群,无需饲养雄蜂,具有种群繁育成本低,生防应用潜力突出等优点。本研究旨在明确环境温度对芙新姬小蜂孤雌产雌品系控害潜力的影响,为该蜂的低成本规模化繁育、田间释放等应用实践提供参考。【方法】在室内以美洲斑潜 蝇Liriomyza sativae 2龄末至3龄初幼虫为寄主,统计4个温度(22, 26, 30和34℃)下芙新姬小蜂孤雌产雌品系雌成虫的取食致死寄主数、寄生致死寄主数、叮蛰致死寄主数、总致死寄主数、日均致死寄主数和成蜂寿命等生活史和控害参数。【结果】随温度升高,芙新姬小蜂孤雌产雌品系雌成虫对美洲斑潜蝇幼虫取食致死寄主数、寄生致死寄主数、叮蛰致死寄主数、总致死寄主数和日均总致死寄主数呈现先增加后降低的趋势,其中取食致死寄主数、寄生致死寄主数和叮蛰致死寄主数在30℃下最高,分别为236.1, 69.2和49.7头;在34℃下最低,分别为115.2, 19.8和21.6头。总致死寄主数在26℃(282.4头)和30℃(355.0头)下显著高于22℃(194.5头)和34℃下(156.5头);日均总致死寄主数在30℃下最高(25.5头)。此外,随着环境温度升高,芙新姬小蜂孤雌产雌品系雌成虫的寿命逐渐缩短,在22℃下最长(16.9 d),在34℃下最短(7.2 d)。【结论】尽管高温缩短了芙新姬小蜂孤雌产雌品系成虫的寿命,但其在30℃下控害能力较强,说明芙新姬小蜂孤雌产雌品系成虫可在30℃高温条件下对耐高温的斑潜蝇如美洲斑潜蝇发挥其控害潜力。     

食物浓度和品系对萼花臂尾轮虫生殖期历时和混交雌体形成的影响

应用单个体培养方法比较研究了藻类食物浓度(2.0、5.0、8.0和11.0×106cells/mL)和品系对采自广州、青岛和芜湖等地的萼花臂尾轮虫生殖期历时、后代数和后代中混交雌体百分率的影响。结果表明,食物浓度对轮虫的生殖期历时和轮虫全部后代中的混交雌体百分率有显著的影响,但对轮虫的总后代数无显著的影响。品系对轮虫的生殖期历时、总后代数和全部后代中的混交雌体百分率均有显著影响。3品系间,广州品系轮虫的生殖期历时最长,为(4.53±0.19)d;总后代数最多达(18.75±0.26)个;全部后代中的混交雌体百分率最低,仅为4.32%±0.51%。而青岛品系轮虫全部后代中的混交雌体百分率最高,达49.90%±2.15%;其生殖期历时和总后代数与芜湖品系间均无显著的差异。食物浓度和品系间的交互作用仅对轮虫全部后代中的混交雌体百分率有显著影响。3品系中,仅芜湖品系轮虫的生殖期历时、总后代数和全部后代中的混交雌体百分率受食物浓度的显著影响;母体年龄对轮虫每天所产后代中的混交雌体百分率的影响因轮虫品系的不同和培养时所用的食物浓度的不同而异。     

家蚕不同品系卵巢管数目变异及其与造卵数的关系

选取西南大学家蚕Bombyx mori基因库中157个品系及杂交材料的雌蛾进行解剖和观察,调查了卵巢管数目的多样性,并初步研究了其生物学特性。结果发现,家蚕资源品系大范围存在雌蛾卵巢管数目变异现象。157个品系及其杂交材料中有87个发生了卵巢管数目变异现象,占55.41%,变异类型有11种。不同类品系间卵巢管数目变异率差别显著,其中突变品系的变异率最高,达60.19%;突变系杂交材料的变异率最低,有37.50%。在发生卵巢管数目变异的突变品系中,个体变异率最高达50%,最低为2%。调查部分品系发现,品系内卵巢管数目增加并不见总造卵数一定增加,而单根卵巢管平均造卵数均低于（4,4）正常型。通过对实用型品系21-871和突变系06-051上下世代雌蛾的解剖观察,发现这两个品系的上下代雌蛾卵巢管数目均有相近的变异趋势,提示卵巢管数目变异有遗传性。     

四川丽蝇族三新种：双翅目：丽蝇科

１９８０－１９９４年在四川一些地区采获的蝇类标本中,发现丽蝇族Ｃａｌｌｉｐｈｏｒｉｎｉ３新种,分别命名为二郎山蚓蝇Ｏｎｅｓｉａ ｅｒｌａｎｇｓｈａｎｅｎｓｉｓ ｓｐ．ｎｏｖ．花蚓蝇Ｏｎｅｓｉａ ｆｌｏｒａ ｓｐ．ｎｏｖ．大叶陪丽蝇Ｂｅｌｌａｒｄｉａ ｍｅｇａｌｏｂａ ｓｐ．ｎｏｖ．,模式示本存于作者所在单位。     

萼花臂尾轮虫休眠卵大小变异在其生活史对策中的作用

以周期性孤雌繁殖的淡水浮游生物——萼花臂尾轮虫（Brachionus calyciflorus）为研究对象．对其安徽品系的休眠卵进行了大、中、小分组,在2个不同食物浓度条件下培养并观察其种群增长、有性生殖方面的特点,以及后代形态大小和新产休眠卵大小。实验发现休眠卵大小对轮虫种群瞬时增长率、混交雌体百分率和后代形态均没有显著影响;而食物浓度则对轮虫种群的瞬时增长率有显著影响;休眠卵大小和食物浓度均显著影响后代休眠卵的大小。     

脑脊膜炎病原菌基因组测序与疫苗开发

英国与美国科学家宣布他们已完成细菌Ｎｅｉｓｓｅｒｉａｍｅｎｉｎｇｉｔｉｄｉｓ中品系Ａ与Ｂ基因组的测序。Ｎ .ｍｅｎｉｎｇｉｔｉｄｉｓ共有十几个品系 ,主要是Ａ、Ｂ、Ｃ这三个品系可导致脑脊膜炎。科学家发现该菌的Ａ与Ｂ品系所含基因数多于 2 10 0个 ,Ｂ品系中只有 6 0 %的基因有明显功能 ,而Ｂ品系中有将近 2 0 0个基因在Ａ品系中不出现。少数基因编码毒素等蛋白质 ,这可以解释为什么该菌不同的品系对人有不同的影响。由于该菌Ｂ品系的荚膜多糖与人的多糖分子完全相同 ,故基于荚膜多糖的疫苗可能引起人的自身免疫疾病。现在科学家…     

香蕉试管苗变异因素的初步研究

本文初步研究了香蕉离体培养中,培养基内不同激素浓度、继代培养数,以及３个品种（品系）对试管苗变异的影响。结果表明：６３１和台湾８号比威廉斯（Ｗｉｌｌｉａｍｓ）稳定,培养条件相同,培养代数多时,变异率明显提高。外源激素的配比试验表明：ＩＢＡ∶ＢＡ为０．５∶４．０（ｍｇ／Ｌ）为最佳配方,当ＩＢＡ∶ＢＡ达到２．０∶１０（ｍｇ／Ｌ）时,异常苗发生率最高。用田间变异株根尖细胞染色体观察结果,发现其染色体数不是增多就是严重缺失。变异株的过氧化物酶同工酶酶谱经电泳分析,表明在迁移率为０．７处的一条带纹消失,而正常对照苗则稳定存在。     

用团头鲂精子诱导金鱼雌核发育研究

本文用紫外灭活的团头鲂(Megalobrama amblycephala)精子激活金鱼 (Carassius auratus Goldfish)卵子,用0－4℃冷水冷休克处理卵子使其染色体加倍,得到成活的雌核发育金鱼。使用与金鱼不同亚科的团头鲂精子做为激活源能极大提高雌核发育后代的鉴定效率,只需依据外形特征、染色体数目和性腺发育程度,就能容易地将雌核发育金鱼和与团头鲂杂交后代区分开。雌核发育金鱼有两种体色不同的后代,但都为双尾,体形似金鱼,染色体数目为2n=100,全雌,性腺发育正常;而杂交后代为单尾,体形似鲫鱼,染色体数目为3n=124,性腺发育滞后。本实验为证明金鱼的性别决定方式为XX/XY型提供了细胞遗传学证据。得到两种体色皆不同于母本体色的后代,体色不同可能是基因座位纯化导致后代性状分化,也可能是异精效应导致。     

The effect of B chromosomes on fitness components inAegilops speltoides Tausch

The effect of B chromosomes (Bs) on various components of vigour and fertility inAegilops speltoides was studied. We designed three types of synthetic populations. In the first type we compared plants from the localities Haifa (which has Bs in nature) and Ashkelon (which has not). Non significant differences were found between the plants from both populations, and between B carriers and non carriers among Haifa individuals. In the second synthetic population we compared 0B, 1B, 2B, 3B and 5B plants from Haifa. We found that vigour variables were not affected by the presence of Bs, while fertility variables were significantly correlated with B number, in such a way that 1B plants produce more grains per plant than any other constitution, while 5Bs produce a remarkable deleterious effect. In the third type of synthetic populations we compared plants with 0B and 1B, 0B and 2B, 0B and 3B, and 0B and 5B. In this case we also found that 1B plants were the most fertile, but the variation of reproductive fitness was higher from plot to plot within the same B class than among B classes. We conclude that the effect of B chromosomes on the fitness variables that we have estimated is close to neutrality in this species. We discuss the relation between the strength of the mechanism of accumulation and the deleterious effects of B chromosomes.     

Chromosome banding and genome compartmentalization in fishes

The diploid chromosome number of the Chinese raccoon dog varies from 54 (no B chromosomes) to 58 (4 B chromosomes). The B chromosomes are totally heterochromatic. An electron microscopic study was made of the synaptonemal complexes (SC) in spermatocytes of these animals. The SC karyotype consists of 27 regular chromosome pairs (autosomes and the sex chromosomes) plus the B chromosomes. The Bs pair effectively with one another at pachytene, but the SC axes of the B chromosomes are much denser than those of the A chromosomes. Depending on the number of Bs, both bivalents and multivalents have been observed. When three B chromosomes are present in a cell, parallel alignment of all three SCs can be seen. Formation of multivalents indicates high homology among these supernumerary heterochromatic chromosomes. Fusiform bulges are found along unpaired regions of all chromosomes which are particularly pronounced in diplotene.     

Wolbachia interactions that determine Drosophila melanogaster survival

Abstract.— We have recently described a mutualistic symbiosis in which Wolbachia bacteria were shown to improve the fitness of some Drosophila melanogaster stocks. Wolbachia did not extend longevity in all Drosophila genotypes, even though 16s rDNA sequences indicated that our Drosophila stocks were infected with the same Wolbachia strain. Here, we use reciprocal hybrid crosses between two Drosophila strains, one that lived longer with Wolbachia (Z53) and one that did not (Z2), to investigate the inheritance of the survival phenotype and its dependence on the host genotype, sex, and mating conditions. Wolbachia's positive effects were more apparent in hybrid flies than in parental flies, ruling out exclusive maternal inheritance or the dependence of the survival phenotype on Wolbachia strain differences. The Wolbachia survival effects were more apparent in single-sex cages, where courtship and mating were not permitted. In these cages, nearly all flies with Wolbachia lived longer than uninfected flies, even though strain Z2 showed no Wolbachia effect in mixed-sex mating cages. We used comparisons between single- and mixed-sex cages to estimate the cost of reproduction for both sexes. Our data suggest that Wolbachia infection may increase the inferred cost of reproduction, particularly in males. Wolbachia can even produce a positive survival effect almost as large as the negative survival effect associated with reproduction. We discuss the implications of our experiments for the study of insect symbioses.     

Interspecific transfer of bacterial endosymbionts between tsetse fly species: infection establishment and effect on host fitness

Tsetse flies (Glossina spp.) can harbor up to three distinct species of endosymbiotic bacteria that exhibit unique modes of transmission and evolutionary histories with their host. Two mutualist enterics, Wigglesworthia and Sodalis, are transmitted maternally to tsetse flies' intrauterine larvae. The third symbiont, from the genus Wolbachia, parasitizes developing oocytes. In this study, we determined that Sodalis isolates from several tsetse fly species are virtually identical based on a phylogenetic analysis of their ftsZ gene sequences. Furthermore, restriction fragment-length polymorphism analysis revealed little variation in the genomes of Sodalis isolates from tsetse fly species within different subgenera (Glossina fuscipes fuscipes and Glossina morsitans morsitans). We also examined the impact on host fitness of transinfecting G. fuscipes fuscipes and G. morsitans morsitans flies with reciprocal Sodalis strains. Tsetse flies cleared of their native Sodalis symbionts were successfully repopulated with the Sodalis species isolated from a different tsetse fly species. These transinfected flies effectively transmitted the novel symbionts to their offspring and experienced no detrimental fitness effects compared to their wild-type counterparts, as measured by longevity and fecundity. Quantitative PCR analysis revealed that transinfected flies maintained their Sodalis populations at densities comparable to those in flies harboring native symbionts. Our ability to transinfect tsetse flies is indicative of Sodalis ' recent evolutionary history with its tsetse fly host and demonstrates that this procedure may be used as a means of streamlining future paratransgenesis experiments.     

The comparison of intrinsic rates of increase among chromosome-substituted lines resistant and susceptible to organophosphate insecticides in Drosophila melanogaster

To investigate the genetic basis of the seasonal fluctuations in resistance to three organophosphates, observed within a natural population of Drosophila melanogaster (Meigen), we compared the intrinsic rate of increase, generation time and net reproduction rate among chromosome substitution lines derived from a resistant and a susceptible line, obtained from this natural population. There was significant variation among substituted lines; lines possessing the third chromosome from the resistant line, which confers resistance to the three organophosphates, generally showed lower mean values of these fitness measures. Chromosomal analyses also indicated significant negative contributions of the third chromosome from the resistant line. However, significant positive contributions of the interactions among chromosomes from the resistant line to these fitness measures were also detected. We further conducted a local stability analysis, in which each chromosome-substituted line was assumed to be introduced at a low frequency into the initial susceptible population. It was demonstrated that the resistance factor(s) on the third chromosome tend to decrease in their frequency under both density-independent and juvenile density-regulated conditions. Based on these results, a possible explanation for the seasonal fluctuations in resistance to the three organophosphates observed in the natural population was proposed.     

Fitness Effects of Ems-Induced Mutations on the X Chromosome of DROSOPHILA MELANOGASTER. II. Hemizygous Fitness Effects

X chromosomes mutagenized with EMS were tested for their effects on the fitness of hemizygous carriers. The tests were carried out in populations in which treated and untreated X chromosomes segregated from matings between males and attached-X females; the populations were maintained for several generations, during which time changes in the frequencies of the treated and untreated chromosomes were observed. From the rates at which the frequencies changed, the fitness effects of the treated chromosomes were determined. It was found that flies hemizygous for a mutagenized chromosome were 1.7% less fit per mM EMS treatment than those hemizygous for an untreated chromosome. Since the same flies were only 0.5% per mM less viable than their untreated counterparts, the total fitness effect of an X chromosome carrying EMS-induced mutants is three to four times greater than its viability effect. By comparing the heterozygous effect of a mutagenized X chromosome on fitness with the corresponding hemizygous effect, the dominance value for the chromosome is estimated to be about 0.25.     

The cytology of Brachycome

Over 1,000 plants of B. dichromosomatica have been counted. 10% of these carried one, two or three B chromosomes. The B chromosome is large, and though it is not heteropycnotic it condenses precociously at mitosis. It behaves regularly at mitosis, and when two are present they pair regularly at meiosis. Non-disjunction and preferential distribution of the B to the generative nucleus occurs at the first pollen grain mitosis, with very high frequency. This is corroborated by data from crosses, which also indicate that the transmission of the B through the female gamete is normal. — The frequency of B chromosomes in marginal populations of var. dichromosomatica is significantly higher than in central populations. In one population of var. alba the frequency of Bs increased significantly after two very dry seasons. It is suggested that both these cases of increased frequency were in response to a selective advantage of plants with Bs under arid conditions. — Plants with one B chromosome appear to be less fit than plants with 2 Bs. The combination of the calculated effects of the nondisjunction mechanism and the inferred relative fitness of the 0B, 1B and 2B plants, provides a reasonable explanation of the observed frequencies of the 0B, 1B and 2B plants in the populations studied.     

Morphology and Meiotic/Mitotic Behavior of B Cromosomes in a Japanese Harvestman, Metagagrella tenuipes (Arachnida: Opiliones): No Evidence for B Accumulation Mechanisms

Earlier, it has been demonstrated that wild populations of a Japanese harvestman Metagagrella tenuipes (Arachnida: Opiliones) are polymorphic for B chromosomes. In this paper, we present results of a study of the morphology and mitotic and meiotic behavior of the Bs. The B chromosomes varied considerably in size and proportion of eu- and heterochromatin. The single nucleolus organizing region, found in males, was located on a chromosome of the A complement. Some intercell variation in number of Bs may be explained by accidental chromosome losses during chromosome preparation. We also found no intertissue variation in number of Bs. There were also no differences in mean number of B chromosomes per individual among males and females, adult and subadult harvestmen. Segregation of Bs in mitotic and meiotic divisions was nonrandom; B chromosomes tended to segregate equally between daughter cells. The results obtained provide no support for the hypothesis of existence of B accumulation mechanism in this species.     

A Wolbachia-associated fitness benefit depends on genetic background in Drosophila simulans

The alpha-proteobacteria Wolbachia infect a number of insect species and influence host reproduction to favour the spread of infected females through a population. The fitness effect of this infection is important in understanding the spread and maintenance of Wolbachia within and among host populations. However, a full elucidation of fitness effect requires careful control of host genetic background. Here, I transferred a single clone of Wolbachia (the wHa strain) into three genetically distinct isofemale lines of the fly Drosophila simulans using microinjection methodology. These lines carried one of the three described mitochondrial haplogroups (siI, siII or siIII) and differ in nuclear genome as well. Population cage assays showed that wHa-infected siIII flies enjoyed a dramatic fitness benefit compared to uninfected siIII. In contrast, wHa did not affect the fitness of siI or siII flies. This study points to the importance of host-by-symbiont interaction terms that may play an important role in organismal-fitness.