三种小花蝽核型研究(半翅目:花蝽科)

本文利用姬姆萨染色压片法对花蝽科小花蝽属3个种:荷氏小花蝽Orius horvathi(Reuter),微小花蝽Oriusminutus Linnaeus和东亚小花蝽Orius sauteri(Poppius)的核型做了研究,结果表明3种小花蝽单倍体均具有12条染色体,X-Y性别决定机制,但3种核型行为具特定的差异,其核型特征可用于种间分类。     

2种辉蝽的精巢和染色体研究(半翅目:蝽科)

通过探讨中国蝽科Pentatomidae辉蝽属Carbula的红角辉蝽Carbula crassiventris(Dallas,1849)和北方辉蝽C.putoni(Jakovlev,1876)的精巢形态和染色体的核型及减数分裂行为,为蝽科昆虫的细胞分类学提供新资料。采用显微形态解剖法和染色体制片法对其精巢和染色体进行观察。结果表明:2种精巢的位置、外被颜色、形状及精巢叶的数目都一致;染色体组成均为2n(♂)=14(12A+XY),具有X-Y性别决定机制。在减数分裂过程中,常染色体前减数分裂,性染色体后减数分裂且无交叉;在中期-Ⅱ,常染色体排列成环状而性染色体在环中央形成假二价体。但是,2个物种在弥散期常染色体的去固缩程度,终变期常染色体双交叉的个数及中期-Ⅰ常染色体和性染色体的排列方式都各不相同。本文证实了蝽科昆虫的减数分裂行为在不同属间、种间可不相同,而且具有一定的属、种间特异性;同时为精巢在蝽类昆虫分类中的作用提供新的资料。     

蝽科精巢细胞减数分裂染色体行为及其反映的属种间亲缘关系

为探讨蝽科精巢细胞减数分裂各时期染色体形态和行为差异, 以及据此反映的属种间亲缘关系, 采用常规染色体制片法对蝽科6属9种精巢细胞减数分裂各期染色体形态特征、 行为及精子的形成进行了观察和比较研究。结果表明： 蝽科精巢细胞为交叉型减数分裂, “O”型交叉为其典型交叉减数分裂形式。各属种减数分裂各期染色体行为相似, 但形态不同。减数分裂各期染色体形态、 排列方式, 中期染色体相对长度、 组成与核型以及精子形态等特征具有属种间差异性。蝽科精巢细胞中期Ⅰ染色体组平均相对长度都为12.5, 在进化过程中染色体组长度信息总量不变。基于染色体相对长度的聚类分析结果显示, 菜蝽属Eurydema、 麦蝽属Aelia、 珠蝽属Rubiconia和条蝽属Graphosoma亲缘关系密切, 而二星蝽属Stollia与果蝽属Carpocoris关系较近。     

军配盲蝽和南方小花蝽对茶网蝽若虫的捕食作用

茶网蝽Stephanitis chinensis是一种为害春茶的重要害虫，本文研究了天敌军配盲蝽Stethoconus japonicus和南方小花蝽Orius similis对茶网蝽的捕食能力，为茶网蝽的生物防治提供科学依据。在室内开展军配盲蝽和南方小花蝽对茶网蝽3龄若虫的捕食功能反应和寻找效应以及南方小花蝽的种内干扰反应研究。结果表明军配盲蝽和南方小花蝽对茶网蝽3龄若虫的捕食功能反应均符合Holling Ⅱ型。军配盲蝽和南方小花蝽的捕食量与茶网蝽3龄若虫的密度呈正相关，但寻找效应与猎物密度呈负相关。南方小花蝽成虫、3龄若虫对茶网蝽3龄若虫的日最大捕食量（11.49头、12.82头）大于军配盲蝽成虫、3龄若虫（10.10头、6.41头）；军配盲蝽成虫对茶网蝽的寻找效应高于其3龄若虫，而南方小花蝽3龄若虫的寻找效应高于成虫。南方小花蝽成虫、3龄若虫对茶网蝽3龄若虫的捕食作用均存在种内干扰反应，且符合Hassell模型，分别为E=0.4263P^-0.825和E=0.5234P^-0.762。综上研究结果，军配盲蝽和南方小花蝽对茶网蝽3龄若虫的捕食作用较强，均具有良好的生物防治潜能。     

三种辉蝽的核型研究（半翅目：蝽科）

本首次研究了采于中国的辉蝽属三个种一辉蝽（Carbula obtusangula Reuter)、北方辉蝽（Carbula putoni(Jakovlev),凹肩辉蝽（Carbula sinica Hsiao et Cheng)的核型,结果表明,三个种均具有典型的蝽科核型即：2n(♂）＝14,具有XY性别决定机制,但是三个种的常染色体和性染色体在减数分裂时期的行为以及核型分析的结果和模式图各不相同,而且在北方辉蝽中出现了1－2条超数染色体,这些特点可为辉蝽属昆虫的形态分类及系统发育提供有用的证据。     

山地原花蝽核型研究(半翅目,花蝽科)

采用姬姆萨染色压片法,对花蝽科山地原花蝽性细胞进行了核型研究.结果表明该种单倍染色体组成为n=14A+XY,为无交叉减数分裂,性染色体经历后减数分裂,上述核型特征为阐明臭虫型内不同科的系统发育关系具有重要意义.     

花蝽科中国二新种及二新纪录种记述(半翅目,异翅亚目)

记述花蝽科Anthocoridae2新种:阿拉善肩花蝽Tetraphleps alashanensis sp.nov.,五斑肩花蝽Tetraphleps maculatus sp.nov.,小花蝽属Orius Wolff中国2新纪录种:细鞭小花蝽Orius laticollis laticollis(Reuter),西伯利亚小花蝽Oriussibiricus Wagner。模式标本保存于内蒙古师范大学昆虫研究所标本馆。     

阿维菌素对南方小花蝽的毒杀作用

在室内条件下,研究了阿维菌素两种产品对南方小花蝽的毒杀效果.结果表明,两种产品对南方小花蝽不同虫态均有一定的毒杀作用.成虫、若虫对阿维菌素的敏感性基本相同,而卵的敏感性最低.阿维菌素对南方小花蝽除有直接的毒杀作用外,对其捕食能力也有一定影响.     

蝽科昆虫精巢形态及属种间亲缘关系

为探讨蝽科精巢形态差异,以及据此反映的属种间亲缘关系,对蝽科9属13种昆虫精巢进行了观察和比较研究.结果表明,蝽科精巢形态在属内种间具有相对稳定性,属间、亚科间具有差异性.蝽科输精管种间变异大.基于精巢长度、宽度、面积及长宽比的聚类分析结果显示,斑须蝽属Dolycoris、绿蝽属Nezara、茶翅蝽属Halyomorpha关系较近,并与二星蝽属Eysarcoris形成并列关系.菜蝽属Eurydema、麦蝽属Aelia、珠蝽属Rubiconia亲缘关系密切.而果蝽属Carpocoris与条蝽属Graphosoma形成不同分支的特殊进化关系.因此,蝽科精巢可作为属级、亚科级的形态和数值分类特征.     

五种植物作为南方小花蝽储蓄植物的适合性评价

储蓄植物系统作为一种开放式的天敌饲养系统,越来越多地应用到温室及田间的害虫防治.南方小花蝽 Orius similis Zheng可捕食蓟马、蚜虫等多种害虫,是农业上一类极具应用价值的捕食性天敌.为提高南方小花蝽的控害效果,建立南方小花蝽储蓄植物系统是一种极为有效的方法.为了筛选适用于南方小花蝽保育和增殖的储蓄植物,进而构建南方小花蝽储蓄植物系统,本研究选择了月季Rosa chinensis、长寿花Narcissus jonquilla、辣椒Capsicum annuum、黄瓜Cucumis sativus和蚕豆Vicia faba作为候选的储蓄植物,通过六臂嗅觉仪分析了南方小花蝽对5种植物花朵的气味选择性,同时分析了南方小花蝽在5种植物上的繁殖系数、发育历期、存活率等生物学参数.结果表明43.33％的南方小花蝽雌虫偏好辣椒花朵气味,其次为蚕豆(26.67％);南方小花蝽卵的孵化率在辣椒上最高达到95.59％,其次为蚕豆为80.74％;同时,南方小花蝽卵在蚕豆上的发育历期显著低于另外4种植物,仅有4.92 d.综上所述,本研究初步认为辣椒和蚕豆比较适合用来构建南方小花蝽储蓄植物系统.     

Distribution Patterns of Wolbachia Endosymbionts in the Closely Related Flower Bugs of the Genus Orius: Implications for Coevolution and Horizontal Transfer

Vertical transmission is the primary route of the endosymbiont Wolbachia for its own spread among invertebrate hosts, but horizontal transmission between different hosts is believed to have occurred multiple times. However, it is not well known how Wolbachia commonly spread among closely related hosts. We focused on the closely related species of the minute pirate bugs belonging to the genus Orius, which are important biological control agents in agricultural crops because they are the most useful natural enemy of various tiny pests, such as thrips. Here, we examined five Orius species (Orius sauteri, Orius nagaii, Orius minutus, Orius strigicollis, and Orius tantillus) from eight geographic localities in Japan for Wolbachia infection. Two distinct strains, wOus1 and wOus2, were detected based on Wolbachia surface protein (wsp) gene sequencing. Furthermore, multilocus sequence typing revealed that each of the strains comprised two variants that differed in a single nucleotide. The overall distribution patterns of the two Wolbachia strains were found to differ among host species: prevalent double infection with wOus1 and wOus2 in O. strigicollis; fixation of single infection with wOus2 in O. nagaii; occurrence of single infection with wOus1 in O. sauteri; prevalence of single infection with wOus1 in O. minutus with an exception in a single population; and lack of Wolbachia infection in O. tantillus. Such differences in the distribution patterns of Wolbachia may reflect the evolutionary history of Wolbachia infection among Orius species and/or ecological and physiological differences among the Orius species that determine the invasiveness and maintenance of the two Wolbachia strains.     

The X Chromosomes of Mammals: Karyological Homology as Revealed by Banding Techniques

A comparison of the Giemsa-banding patterns of the X chromosomes in various mammalian species including man indicates that two major bands (A and B), which are resistant to trypsin and urea-treatments, are always present irrespective of the gross morphology of the X chromosomes. This is true in all mammalian species with the "original or standard type" X chromosomes (5-6% of the haploid genome) thus far analyzed. In the unusually large-sized X chromosomes the extra chromosomal material may be due either to the addition of genetically inert constitutive heterochromatin or to an X-autosome translocation. In these X chromosomes two major bands are present in the actual X-chromosome segment. Our data on C and G band patterns also support Ohno's hypothesis that the mammalian X chromosome is extremely conservative in its genetic content, in spite of its cytogenetic variability.     

Cytogenetic evidence for a complex of species within the taxon Anopheles maculatus (Diptera: Culicidae)

Two largely independent studies of chromosomes from natural populations of Anopheles maculatus provide evidence for several genetic species within the taxon. (1) Polytene chromosome variation shows four different rearrangements of arm 2 and three rearrangements of the X chromosome. There is strong evidence for three species. Two allopatric populations represent either dramatic geographic variation for two independent inversion systems within one of the genetic species, or represent two additional species. Their species status remains unresolved by this work. (2) Heterochromatic variation occurs in both X and Y chromosomes as revealed by Giemsa-banding of mitotic chromosomes from larval brains. The distribution and association of these various sex chromosomes give further evidence of a species complex. A preliminary correlation of these two kinds of chromosomal variation is given.     

Aberrant spermatogenesis and the peculiar mechanism of sex determination in Symphypleonan Collembola (Insecta)

Light and electron microscopy evidence have been obtained to describe the peculiar spermatogenesis in the collembolan species Sminthurus viridis and Allacma fusca (Sminthuridae). In these two species, the two sexes differ for the lack of two chromosomes (the sex chromosomes) in males (males, 2n = 10; females, 2n = 12). While oogenesis seems to proceed normally, spermatogenesis is peculiar because the two daughter cells of the first meiotic division have different chromosome numbers (six and four). The cell receiving four chromosomes degenerates, while the cell receiving six chromosomes completes meiosis and produces identical spermatozoa (n = 6). At fertilization, pronuclei with six chromosomes fuse together to form zygotes with 2n = 12. Male embryos must lose two sex chromosomes during the first zygotic mitosis, as all male cells have 2n = 10 chromosomes. The sex chromosome system of these species can be identified as X1X1X2X2:X1X20. Electron microscopy observations show that the same peculiar spermatogenesis occurs also in two others species of the same family, Caprainea marginata and Lipothrix lubbocki. The peculiar sex determination system described is similar but not identical to what is observed in other insect orders, and it may represent an evolutionary step toward parthenogenesis. It is suggested that this peculiar spermatogenesis is common to all Symphypleona.     

Non-homologous sex chromosomes in two species of the genus Eigenmannia (Teleostei: Gymnotiformes)

The Neotropical genus Eigenmannia is a fish group with unknown species diversity where representatives possess a broad range of chromosomal sex determining systems namely XY/XX, X(1)X(2)Y/X(1)X(1)X(2)X(2), ZZ/ZW as well as homomorphic sex chromosomes. To test the homology of two heteromorphic XY sex chromosome systems present in two sympatric populations, reciprocal cross-species FISH experiments were performed using probes derived by microdissection of X and Y chromosomes present in analyzed specimens of Eigenmannia virescens and Eigenmannia sp.2, respectively. While X and Y paint probes hybridized to species-specific sex chromosomes, in reciprocal cross-FISH both probes hybridized exclusively to autosomes. The result suggests multiple independent origins of the XY systems in the analyzed populations.     

Sex chromosome differentiation in Belostoma (Insecta: Heteroptera: Belostomatidae)

Belostoma, a genus of the family Belostomatidae, includes species of great ecological importance as biocontrol agents. Few species of these species have been the subject of cytogenetic analyses. Karyotypic evolution in this genus involves agmatoploidy and simploidy; there are also different sex chromosome systems. We examined two Belostoma species (B. dilatatum and B. candidulum) collected from the Paranapanema River Basin (Brazil). Mitotic and meiotic analysis revealed 2n(♂) = 26 + X(1)X(2)X(3)Y for B. dilatatum and 2n(♂) = 14 + XY for B. candidulum; both karyotypes have holokinetic chromosomes. Differences in heterochromatin distribution were also observed between the species, besides variation in the localization of CMA(3)(+)/DAPI(-) blocks. The existence of different types of sex chromosome systems in these species was confirmed based on arrangements of the chromosomes in different meiotic stages. We identified a new sex system in B. dilatatum, and make the first cytogenetic report on B. candidulum.     

Genome size and determination of DNA content of the X chromosomes, autosomes, and germ line-limited chromosomes of Sciara coprophila

The unique chromosome biology of the fungus fly Sciara coprophila has fascinated investigators for over 80 years. Male meiosis exhibits a monopolar spindle, nonrandom segregation of imprinted chromosomes and nondisjunction of the X chromosome. The unusual mechanism of sex determination requires selective elimination of X chromosomes in embryogenesis. Supernumerary (L) chromosomes are also eliminated from the soma during early cleavage divisions. Distinctive DNA puffs on the larval salivary gland chromosomes are sites of DNA amplification. As a foundation for future genome studies to explore these many unusual phenomena, we have used DNA-Feulgen cytophotometry to determine genome size from hemocyte nuclei of male (X0) and female (XX) larvae and adults. The DNA content of the X chromosome is approximately 0.05 pg DNA and the autosomal complement is approximately 0.45 pg DNA. Measurements of DNA levels for individual sperm from adults showed that the DNA contribution of the germ line-limited (L) chromosomes constitutes as much as 35% of the DNA of the male gamete. A parallel study using Sciara ocellaris, a related species lacking L chromosomes, confirmed the presence of two X chromosomes in the sperm of this species.     

Rapid rise and fall of selfish sex-ratio X chromosomes in Drosophila simulans: spatiotemporal analysis of phenotypic and molecular data

Sex-ratio drive, which has been documented in several Drosophila species, is induced by X-linked segregation distorters. Contrary to Mendel's law of independent assortment, the sex-ratio chromosome (X(SR)) is inherited by more than half the offspring of carrier males, resulting in a female-biased sex ratio. This segregation advantage allows X(SR) to spread in populations, even if it is not beneficial for the carriers. In the cosmopolitan species D. simulans, the Paris sex-ratio is caused by recently emerged selfish X(SR) chromosomes. These chromosomes have triggered an intragenomic conflict, and their propagation has been halted over a large area by the evolution of complete drive suppression. Previous molecular population genetics analyses revealed a selective sweep indicating that the invasion of X(SR) chromosomes was very recent in Madagascar (likely less than 100 years ago). Here, we show that X(SR) chromosomes are now declining at this location as well as in Mayotte and Kenya. Drive suppression is complete in the three populations, which display little genetic differentiation and share swept haplotypes, attesting to a common and very recent ancestry of the X(SR) chromosomes. Patterns of DNA sequence variation also indicate a fitness cost of the segmental duplication involved in drive. The data suggest that X(SR) chromosomes started declining first on the African continent, then in Mayotte, and finally in Madagascar and strongly support a scenario of rapid cycling of X chromosomes. Once drive suppression has evolved, standard X(ST) chromosomes locally replace costly X(SR) chromosomes in a few decades.     

Chromosome evolution in the erythrinid fish, Erythrinus erythrinus (Teleostei: Characiformes)

The genus Erythrinus belongs to the family Erythrinidae, a neotropical fish group. This genus contains only two described species, Erythrinus erythrinus being the most widely distributed in South America. Six samples of this species from five distinct Brazilian localities and one from Argentina were studied cytogenetically. Four groups were identified on the basis of their chromosomal features. Group A comprises three samples, all with 2n = 54 chromosomes, a very similar karyotypic structure, and the absence of chromosome differentiation between males and females. One sample bears up to four supernumerary microchromosomes, which look like 'double minute chromosomes' in appearance. Groups B-D comprise the three remaining samples, all sharing an X(1)X(1)X(2)X(2)/X(1)X(2)Y sex chromosome system. Group B shows 2n = 54/53 chromosomes in females and males, respectively, and also shows up to three supernumerary microchromosomes. Groups C and D show 2n=52/51 chromosomes in females and males, respectively, but differ in the number of metacentric, subtelocentric, and acrocentric chromosomes. In these three groups (B-D), the Y is a metacentric chromosome clearly identified as the largest in the complement. The present results offer clear evidence that local samples of E. erythrinus retain exclusive and fixed chromosomal features, indicating that this species may represent a species complex.