Number of reproductive cycles of Varroa jacobsoni in honey-bee (Apis mellifera) colonies

Very little data exists concerning the number of reproductive cycles performed by individual Varroa mites. To understand the population dynamics of the Varroa mite it is necessary to know the number of fertile female offspring each Varroa female produces during her lifetime. The lifetime reproduction capacity of the mite consists of the mean number of fertile female offspring produced during each reproductive cycle multiplied by the mean number of cell passages. This paper describes an experimental design to estimate the number of reproductive cycles where mites are transferred to new mite-free colonies for reproduction in sealed brood cells. The data presented suggests that the mean number of reproductive cycles performed by the individual female mite is larger than previously accepted. Under optimal conditions, the mean number of reproductive cycles by Varroa females is probably greater than 1.5 but less than 2. Furthermore, the results show that the reproductive success of Varroa females going into cells to reproduce is not influenced by previous brood cycles.     

<Emphasis Type="Italic">FORMOSA</Emphasis> controls cell division and expansion during floral development in <Emphasis Type="Italic">Antirrhinum</Emphasis><Emphasis Type="Italic">majus</Emphasis>

Control of organ size is the product of coordinated cell division and expansion. In plants where one of these pathways is perturbed, organ size is often unaffected as compensation mechanisms are brought into play. The number of founder cells in organ primordia, dividing cells, and the period of cell proliferation determine cell number in lateral organs. We have identified the Antirrhinum FORMOSA (FO) gene as a specific regulator of floral size. Analysis of cell size and number in the fo mutant, which has increased flower size, indicates that FO is an organ-specific inhibitor of cell division and activator of cell expansion. Increased cell number in fo floral organs correlated with upregulation of genes involved in the cell cycle. In Arabidopsis the AINTEGUMENTA (ANT) gene promotes cell division. In the fo mutant increased cell number also correlates with upregulation of an Antirrhinum ANT-like gene (Am-ANT) in inflorescences that is very closely related to ANT and shares a similar expression pattern, suggesting that they may be functional equivalents. Increased cell proliferation is thought to be compensated for by reduced cell expansion to maintain organ size. In Arabidopsis petal cell expansion is inhibited by the BIGPETAL (BPE) gene, and in the fo mutant reduced cell size corresponded to upregulation of an Antirrhinum BPE-like gene (Am-BPE). Our data suggest that FO inhibits cell proliferation by negatively regulating Am-ANT, and acts upstream of Am-BPE to coordinate floral organ size. This demonstrates that organ size is modulated by the organ-specific control of both general and local gene networks. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

A further note on the relationships of the EuropeanLinum hologynum and the Australian species ofLinum (Linaceae)

The diploid chromosome number for the EuropeanLinum hologynum and the haploid number for the AustralianL. monogynum is 42 and appears to establish a new and distinctive base number for sect.Linum. The possession by these two species and by the AustralianL. marginale of multiporate pollen and united styles, a unique combination of features in sect.Linum, may warrant the establishment of a new subsection in that section to accommodate the three species.     

Identification and analysis of the Shewanella oneidensis major oxygen-independent coproporphyrinogen III oxidase gene

Shewanella oneidenesis MR-1 is a facultative anaerobe that can use a large number of electron acceptors including metal oxides. During anaerobic respiration, S. oneidensis MR-1 synthesizes a large number of c cytochromes that give the organism its characteristic orange color. Using a modified mariner transposon, a number of S. oneidensis mutants deficient in anaerobic respiration were generated. One mutant, BG163, exhibited reduced pigmentation and was deficient in c cytochromes normally synthesized under anaerobic condition. The deficiencies in BG163 were due to insertional inactivation of hemN1, which exhibits a high degree of similarity to genes encoding anaerobic coproporphyrinogen III oxidases that are involved in heme biosynthesis. The ability of BG163 to synthesize c cytochromes under anaerobic conditions, and to grow anaerobically with different electron acceptors was restored by the introduction of hemN1 on a plasmid. Complementation of the mutant was also achieved by the addition of hemin to the growth medium. The genome sequence of S. oneidensis contains three putative anaerobic coproporphyrinogen III oxidase genes. The protein encoded by hemN1 appears to be the major enzyme that is involved in anaerobic heme synthesis of S. oneidensis. The other two putative anaerobic coproporphyrinogen III oxidase genes may play a minor role in this process.     

Regulation of Mu element copy number in maize lines with an active or inactive Mutator transposable element system

Summary In the progeny of an active Mutator plant, the number of Mu elements increases on self-pollination and maintains the average parental Mu content on outcrossing to a non-Mutator line; both patterns of transmission require an increase in the absolute number of Mu elements from one generation to the next. The same average copy number of Mu elements is transmitted through the male and female, but there is wide variation in the absolute copy number among the progeny. In inactive Mutator plants —defined both by the loss of somatic instability at a reporter gene (bronze2-mu1) and by modification of the HinfI sites in the terminal inverted repeat sequences of Mu elements —the absolute copy number of Mu elements is fixed in the parent. Thus, in outcrosses Mu element number is halved, and on self-pollination Mu copy number is constant. Reactivation of somatic mutability at cryptic bz2-mu1 alleles in inactive individuals by crossing to an active line seems not to involve an increase in Mu element copy number transmitted by the inactive individual. These and other results suggest that increases in Mu copy number occur late in plant development or in the gametophyte rather than after fertilization.     

油菜类型和品种对外来入侵杂草小子虉草的替代控制作用

外来入侵植物小子虉草（Phalaris minor Retz.）是世界公认的冬季农田恶性杂草,掌握农作物对其替代控制作用具有重要的研究价值。前期研究表明,油菜是替代控制小子虉草的优良农作物,然而,目前尚不清楚油菜类型与品种对其控制能力的影响。为此选取与小子虉草同域发生的不同类型（白菜型油菜、芥菜型油菜和甘蓝型油菜）油菜品种各3种,通过田间小区实验和室内化感作用测定,对比研究其对小子虉草的生长、繁殖、表型以及化感作用的影响。田间实验显示：竞争方式（种内或种间竞争）和油菜类型对小子虉草的地上生物量、种子数、株高、分枝数、叶面积和比叶面积存在极显著（P=0.0001）影响;而油菜品种对小子虉草的地上生物量（P=0.6064）、种子数（P=0.3577）、株高（P=0.4279）、分枝数（P=0.6357）、叶面积（P=0.8839）和比叶面积（P=0.3424）均无显著影响。3种类型油菜对小子虉草生长、繁殖以及表型的影响存在明显差异,其中芥菜型油菜对小子虉草的上述指标的影响最强,而白菜型油菜的影响最弱。室内生物测定显示,油菜对小子虉草具有化感抑制作用,当供试油菜叶片水提液浓度为0.1 g/mL时,小子虉草种子的萌发和幼苗的株高、根长、生物量均被显著抑制;研究也表明不同类型油菜对小子虉草的化感作用显著不同,同等条件下,芥菜型油菜对小子虉草的化感抑制作用最强。综上所述,油菜类型对外来入侵小子虉草的控制作用存在显著差异,其中芥菜型油菜对植物小子虉草的替代控制作用明显优于白菜型油菜和甘蓝型油菜,而其强的化感抑草特性或许是其强控草能力的原因之一。另外,本研究也为进一步利用油菜替代控制入侵植物小子虉草提供了参考。     

Conspecific Sharing of Breeding Sites by Anopheline Female Mosquitoes (Diptera: Culicidae) Inferred from Microsatellite Markers

The number of Anopheles gambiae and Anopheles arabiensis females that used each of the 33 sampled breeding sites in west Kenya was estimated by microsatellite markers and related statistics to test the hypothesis that conspecific females share aquatic sites. Totally, 166 An. gambiae and 168 An. arabiensis larvae were identified and were genotyped. The mean number of larvae per breeding site was 8.3 for An. gambiae and 8.4 for An. arabiensis. The likelihood method estimated that, for An. gambiae, the mean number of females that would have laid eggs per breeding site was 5.2 and ranged from 2 to 9, and for An. arabiensis, the mean was 5.0 with a range of 2–10. The clustering method estimated that the mean number of females laying eggs per breeding site was 6.8 for An. gambiae. The results provide molecular evidence that females of one or both species share breeding sites.     

大鵟对长爪沙鼠秋季的集群捕食策略

2003年9月10日—15日,在内蒙古东乌珠穆沁旗嘎达布其口岸附近的典型草原区鼠害草场研究了大鵟(Buteo hemilasius)对长爪沙鼠的捕食策略。鉴于秋季是长爪沙鼠的活跃期,直接采用鼠丘核心区的沙鼠洞口数作为衡量长爪沙鼠集群大小的指标,分析了大鵟对不同大小集群的长爪沙鼠家族集群的捕食选择偏好。实验涉及了3hm2的实验样地,样地中具有符合实验统计的长爪沙鼠洞群为87个。5d内作者观察到大鵟蹲守在样地中的长爪沙鼠29只次,共涉及23个沙鼠洞群。通过分析大鵟蹲守和没有蹲守过的沙鼠洞群的洞口数量,利用非参数的Mann-Whitney U检验法分析,结果表明:大鵟蹲守的洞群的洞口数量总秩和为2569.5,大鵟没有蹲守的沙鼠洞群的洞口数量秩和统计量为1258.5,统计量U值为489.5。校正之后的Z值为-2.37459,两组差异达到显著的水平(P=0.017574)。此外,分析还显示:沙鼠洞群洞口数量(S)与大鵟蹲守次数(F)呈显著的正相关关系,相关式为:F=-0.0559+0.023×S,(r=0.2707,P﹤0.05)。结果表明,大鵟会首先在洞口数量多的长爪沙鼠集群蹲守捕食,因此在越冬期间,长爪沙鼠的集群数量会被限制,进而可能形成一种最优化集群数量的模式。本文的研究结果从一定角度支持了鼠类通过形成最优集群以降低天敌捕食概率的理论。长爪沙鼠可能借助扩散行为,以及秋季的分群行为来降低集群密度从而降低被捕食风险。     

The influence of parental genotype on the chromosome behaviour of Hordeum vulgare X H. bulbosum diploid hybrids

Summary The PMCs of 74 diploid hybrids involving ten H. vulgare varieties and three H. bulbosum lines were analysed at metaphase I and chromosome number and chiasma frequency recorded. There were differences between parental combinations and between plants within those combinations for both chromosome and chiasma number. It is suggested that these characters are controlled by both parents and that differences between plants within families reflect the heterozygosity of the H. bulbosum parents. Chromosomally stable, high pairing lines have been identified for use in a backcrossing programme to introduce H. bulbosum characters to the H. vulgare germplasm.     

Chromosome cytology and karyotype change inGalaxia (Iridaceae)

Basic chromosome number inGalaxia is believed to be x = 9, and this number, or multiples, occurs in all species of subgenusGalaxia. In subgenusEurystigma, G. barnardii has n = 8,G. versicolor n = 8 and 7,G. citrina n = 8, 7 and 17 whileG. variabilis has n = 7 exclusively. Karyotypes in forms ofG. versicolor with n = 7 and inG. variabilis are quite different and clearly originated independently. Karyotypic features provide evidence for the hypothesis that changes in chromosome number were accomplished through chromosome fusion either by classical Robertsonian translocation, or unequal reciprocal translocation.     

Experimental evidence for pollination of Banksia spp. by non-flying mammals

Summary The importance of non-flying mammals as pollinators of Banksia integrifolia and B. spinulosa was analysed by examining the effect of pollinator exclusions on fruit-set. Visitation by potential pollinators was also measured by observation and by indirect methods. Nonflying mammals were frequent visitors to inflorescences of both Banksia species. The aluminium sleeves used to exclude non-flying mammals from B. integrifolia trees were associated with a reduction in both the number of infructescences produced and the number of fruit per infructescence, indicating that non-flying mammals were important pollinators. Bird-nets over trees also significantly reduced the number of fruit per infructescence, but had no significant effect on the number of infructescences produced. The results of exclusion experiments using single inflorescences were inconclusive due to low fruitset. No conclusions could be drawn from these experiments with B. spinulosa. However, results for B. integrifolia support the conclusions of whole-tree experiments. Analysis of the genotype frequencies in seed from B. integrifolia provided no support for the hypothesis that the relatively limited mobility of non-flying mammal pollinators would cause inbreeding.     

Exceedingly high chromosome number in Strasburgeriaceae, a monotypic family endemic to New Caledonia

We present the first report on the chromosome number of Strasburgeria robusta, which is confined to montane forests of New Caledonia and is the only known species in Strasburgeriaceae. The species has 2n = 500, which is an exceedingly high chromosome number in angiosperms. Within Crossosomatales, molecular evidence has indicated that S. robusta is sister to Ixerba brexioides, which is endemic to New Zealand and is the sole species in Ixerbaceae. Comparisons to the chromosome number of I. brexioides (2n = 50) support a close affinity between the two species because they share the base number x = 25. It is generally accepted that an increase in ploidy is associated with the origin of novel adaptations. A high level of polyploidy (20x with x = 25) may have allowed S. robusta to survive on a fragment of Gondwana by adapting to its ultrabasic substrate.     

Diversification and Independent Evolution of Troponin C Genes in Insects

Troponin C (TpnC), the calcium-binding subunit of the troponin regulatory complex in the muscle thin filament, is encoded by multiple genes in insects. To understand how TpnC genes have evolved, we characterized the gene number and structure in a number of insect species. The TpnC gene complement is five genes in Drosophilidae as previously reported for D. melanogaster. Gene structures are almost identical in D. pseudoobscura, D. suboboscura, and D. virilis. Developmental patterns of expression are also conserved in Drosophila subobscura and D. virilis. Similar, but not completely equivalent, TpnC gene repertoires have been identified in the Anopheles gambiae and Apis mellifera genomes. Insect TpnC sequences can be divided into three groups, allowing a systematic classification of newly identified genes. The pattern of expression of the Apis mellifera genes essentially agrees with the pattern in Drosophilidae, providing further functional support to the classification. A model for the evolution of the TpnC genes is proposed including the most likely pathway of insect TpnC diversification. Our results suggest that the rapid increase in number and sequence specialization of the adult Type III isoforms can be correlated with the evolution of the holometabolous mode of development and the acquisition of asynchronous indirect flight muscle function in insects. This evolutionarily specialization has probably been achieved independently in different insect orders.Reviewing Editor: Dr. Rüdiger Cerff     

Effects of the infection of toxigenic fungi and an antagonistic Streptomyces strain on wheat spikes

The objective of the present study was to determine the effect on infection of wheat spikes by toxigenic fungi (Aspergillus parasiticus NRRL 2999, Fusarium tricinctum NRRL 3299, Fusarium graminearum CEREMIC 136/92) and a strain of Streptomyces sp. that is antagonistic to the above-mentioned fungi. Wheat grains (variety GRANERO INTA) were sown in 8 pots containing natural soil and kept in a greenhouse chamber. In the period of the early anthesis the wheat spikes were inoculated with conidial suspensions of each of the fungi in the presence or absence of Streptomyces. Each pot was assigned a different treatment. After an incubation of 100 days and when the wheat plants had attained maturity, the spikes were separated and the following items were determined: (a) number of grains obtained with each treatment, (b) weight of the grains, (c) average weight of the grains/treatment, (d) average number and weight of the grains/spike, and (e) invasion of the caryopses by the microorganisms determined by the analysis of the caryopses in seriate histological sections.There was a significant decrease (p<0.01) in the average weight of the caryopses and in the weight and number of grains/spike in the presence F. graminearum. The wheat grains were invaded by of F. graminearum and A. parasiticus, an effect which was partially attenuated by the presence of antagonist Streptomyces sp. Nevertheless, the effect was not strong enough to prevent the degenerative consequences on the size and weight of the grains produced by F. graminearum.     

The effects of Acanthaster planci predation on populations of two species of massive coral

Species of the freshwater planarian genus Polycelis have a variable number of eyes in the head, typically more than a hundred. To elucidate the mechanisms determining the number of eyes, we investigated the relation between eye number and body length in Polycelis sapporo (Ijima & Kaburaki), a non-fissioning species, and P. auriculata Ijima & Kaburaki, a fissioning species. In P. sapporo reared at 7–8 °C, a positive correlation existed between number of eyes and body length. Eye number decreased with starvation. A similar correlation was true of P. auriculata. In specimens of P. auriculata undergoing regeneration, the rate of eye formation was higher in newly formed heads originating from larger tail-pieces than in those from smaller pieces. As a head regenerated from a tail piece or as the body size increased with feeding, the number of eyes increased. These results suggest that the number of eyes in an individual of Polycelis is determined by body length. The fine structure of the photoreceptor and pigment cells in the eyes of P. auriculata is similar to that of comparable cells in the pair of eyes in Dugesia despite the difference in the number of cells comprising an eye.     

Taxonomic and functional implications of stigma morphology in species ofCassia,Chamaecrista, andSenna (Leguminosae:Caesalpinioideae)

Two stigma forms occur inChamaecrista andSenna, but only one inCassia. In the common chambered form, a stigma pore is positioned on the reflexed style tip and is the entrance to a tapering chamber. The pore rim is fringed by hairs which vary in number, size, distribution and shape. In the alternative form the stigma is situated at the apex of the curved style and is crateriform. The crater rim is fringed by hairs of variable number and shape. The stigmatic hairs are predominantly unicellular and cutinized. Stigma and hair differences aid in the taxonomy of the genera. Their functions in pollination biology are discussed.     

TrnL-trnF sequence data imply paraphyly of Aquilaria and Gyrinops (Thymelaeaceae) and provide new perspectives for agarwood identification

The genera Aquilaria and Gyrinops (Thymelaeaceae, Malvales) are well known for the production of agarwood which is a highly wanted forest product of substantial economic value. The taxonomic status of Aquilaria and Gyrinops as separate genera is doubted as they are only distinguished by the number of stamens. We investigated their status by conducting phylogenetic analyses of DNA sequences from the plastid trnL-trnF spacer. Control of international trade of agarwood is currently hampered by the failure of traditional methods such as microscopy to identify samples to species level. We therefore evaluated the potential of molecular identification of agarwood by searching for species- and region-specific plastid DNA polymorphisms. DNA sequences were obtained from 31 Thymelaeaceae accessions encompassing 20 different species in six genera. Aquilaria and Gyrinops appear to be paraphyletic. Success in sequencing wood samples demonstrates that molecular markers provide new perspectives for agarwood identification.     

商陆属2种植物花器官发生过程观察

该研究采用扫描电镜观察红蕊商陆(Phytolacca esculenta)和浙江商陆(Phytolacca zhejiangensis)的花器官发生过程,以明确商陆属植物花的基数,以及雄蕊和雌蕊是否具有叶性器官发生的特点,阐明商陆属植物花发生的模式。观察结果显示:(1)红蕊商陆和浙江商陆在花原基发生后,小苞片以2/5圆周相继发生,花被片的发生紧接小苞片的发生进行,花被与小苞片的发生均有顺时针和逆时针方向,且二者的发生方向始终一致。(2)花被发生结束后,雄蕊在花顶端分生组织的环状分生组织上发生,没有明显的发生顺序,近似同时发生;2轮雄蕊时内轮雄蕊先发生;外轮雄蕊有少数有时偶然与花被互生,但因外轮雄蕊数多于花被数,雄蕊与花被常不互生,也没有规律性。(3)红蕊商陆和浙江商陆的心皮都在雄蕊发生后,紧接着开始发生,且雌蕊与雄蕊(或内轮雄蕊)互生发生;心皮没有发生的先后次序,且每个心皮在基部连成一个整体形成雌蕊基部并发育成为子房。(4)红蕊商陆和浙江商陆的花基数为5,雄蕊和雌蕊的发生及数目不符合5基数的特点。研究认为,红蕊商陆和浙江商陆为5基数花,该研究结果不支持商陆属植物为3基数花的发生模式。     

Microgametophytic plastid nucleoid content and reproductive and life history traits of tribeTrifolieae (Fabaceae)

Microgametophytic plastid nucleoids were quantified for 18 species representing the four core genera of the tribeTrifolieae (Fabaceae),Medicago, Melilotus, Trigonella, andTrifolium. Generative cells of all taxa contained nucleoids, establishing that biparental plastid inheritance is common in theTrifolieae. Nucleoid number and volumes of pollen grains and generative cell nuclei differed among taxa. Nucleoid number was positively correlated with pollen grain and generative cell nuclear volumes, flower size and style length. These relationships disappeared after adjusting nucleoid number for pollen grain and generative cell nuclear volumes. Adjusted nucleoid numbers provided no evidence to support hypotheses that plastid content is associated with ploidy level, mating system, perenniality or size of the reproductive apparatus.