Development of species‐specific primers for rapid diagnosis of Tetranychus urticae,T. kanzawai,T. phaselus and T. truncatus (Acari: Tetranychidae)

Species diagnosis is of the utmost importance to both pest management and plant quarantine services. Because of difficulties in the morphological diagnosis of spider mites, molecular techniques are of great value to rapidly and accurately diagnose closely related species. We examined four species of genus Tetranychus (the green and red forms of T. urticae, and T. kanzawai, T. phaselus and T. truncatus), which are found in Korea and are of significance to plant quarantine services. DNA samples isolated from a single egg, larva or adult weighed 64–188 ng. We designed species‐specific primers by performing sequence alignment for 107 sequences of the ribosomal internal transcribed spacer 2 (ITS2) region, which we obtained from GenBank, and sequences generated in this study. Specific nucleotides of each species were selected for designing primers specific for each species. Each species‐specific primer pair, when used to perform PCR analyses, detected only the species from which it originated. However, a T. urticae‐specific primer pair did not discriminate between the green and red forms of this species. These species‐specific primers can be applied in practice for the rapid and accurate diagnosis of spider mite species in plant quarantine and in agricultural fields.     

Population genetic evidence for sex‐specific dispersal in an inbred social spider

Dispersal in most group‐living species ensures gene flow among groups, but in cooperative social spiders, juvenile dispersal is suppressed and colonies are highly inbred. It has been suggested that such inbred sociality is advantageous in the short term, but likely to lead to extinction or reduced speciation rates in the long run. In this situation, very low levels of dispersal and gene flow among colonies may have unusually important impacts on fitness and persistence of social spiders. We investigated sex‐specific differences in dispersal and gene flow among colonies, as reflected in the genetic structure within colonies and populations of the African social spider Stegodyphus dumicola Pocock, 1898 (Eresidae). We used DNA fingerprinting and mtDNA sequence data along with spatial mapping of colonies to compare male and female patterns of relatedness within and among colonies at three study sites. Samples were collected during and shortly after the mating season to detect sex‐specific dispersal. Distribution of mtDNA haplotypes was consistent with proliferation of social nests by budding and medium‐ to long‐distance dispersal by ballooning females. Analysis of molecular variance and spatial autocorrelation analyses of AFLPs showed high levels of genetic similarity within colonies, and STRUCTURE analyses revealed that the number of source populations contributing to colonies ranged from one to three. We also showed significant evidence of male dispersal among colonies at one site. These results support the hypothesis that in social spiders, genetic cohesion among populations is maintained by long‐distance dispersal of female colony founders. Genetic diversity within colonies is maintained by colony initiation by multiple dispersing females, and adult male dispersal over short distances. Male dispersal may be particularly important in maintaining gene flow among colonies in local populations.     

Effect of 9.6-GHz pulsed microwaves on the orb web spinning ability of the cross spider (Araneus diadematus)

Eight cross spiders (Araneus diadematus) were exposed overnight (16 h) during web-building activity to pulsed 9.6-GHz microwaves at average power densities of 10, 1, and 0.1 mW/cm2 (estimated SARs 40, 4, and 0.4 mW/g). Under these conditions, 9.6-GHz pulsed microwaves did not affect the web-spinning ability of the cross spider.     

中国树蛛属(蜘蛛目:蟹蛛科)一新种

本文记述蜘蛛目蟹蛛科一新种——新疆树蛛Diaea xinjiangensis sp. nov.。本新种与Diaeadorsata(Fabricius)和D. pictilis(Banks)相近似,但其外雌器和触肢器的构造与后两种有明显区别。     

Control of sex ratio by female spider mites

Control of sex ratio in the progenies of mated female spider mites was investigated in two laboratory experiments. In Experiment I, a single strain of Tetranychus urticae Koch was reared in four different environments. In Experiment II, 4 different geographic strains of T. urticae were reared in a single environment.Results indicated that spider mite females were able to control the sex ratio of their progeny at two levels: an initial control of mean population ratio according to ovipositional environment. In addition, a secondary control resulted in an approximately uniform daily ratio. Although each parental female produced a varying number of eggs from day to day, a more or less constant fraction of those eggs were fertilized every day. It is concluded that both of these characteristics are probably important to the colonizing ability of the species.

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Résumé L'étude de la régulation du sexe de la descendance de femelles inséminées d'acariens est basée sur deux expériences de laboratoire. Dans l'expérience I, une lignée de Tetranychus urticae a été élevée dans deux conditions différentes de qualité des feuilles pendant le développement des parents, d'une part, pendant leur ponte et le développement de la descendance d'autre part. Dans l'expérience II, quatre souches géographiques différentes de T. urticae ont été élevées dans les mêmes conditions.Il est apparu nettement que les femelles dans des conditions différentes ont donné des descendances avec des taux sexuels variant dans certaines limites. Ces différences étaient statistiquement significatives dans les duex lots de données expérimentales. Les taux sexuels des populations d'acariens variaient aussi avec les conditions écologiques. Dans les bonnes conditions, la proportion de femelles dans la descendance était la plus élevée. Les taux sexuels des populations variaient aussi entre les quatre souches géographiques.Les analyses ont aussi révélé que les femelles d'acariens sont capables de contrôler le taux sexuel à deux niveaux: une régulation initiale du taux de la population en fonction des conditions écologiques ou de la lignée géographique et un contrôle secondaire qui s'est traduit par un taux quotidien approximativement uniforme.En utilisant un argument mathématique simple incorporant la fécondité caractéristique des acariens, nous avons conclu que ces deux caractéristiques de la rulation sont probablement d'une importance capitale pour le pouvoir colonisateur de cette espèce.

     

The Action of Black Widow Spider Venom on Cholinergic Mechanisms in Synaptosomes

Abstract: Black widow spider venom (BWSV) promoted the massive release of labeled acetylcholine from synaptosomes and in addition, inhibited high-affinity choline uptake into the preparation. Both activities occurred in the absence of [Ca²⁺]₀. When Na⁺ in Krebs-Ringer was replaced isotonically by sucrose, BWSV did not cause any release of [³H]ACh. On the other hand, BWSV was still effective if Na⁺ was replaced by lithium, glucosamine, or Tris. Tetrodotoxin (10^?5 M) failed to prevent the ACh-releasing action of the venom. The uptake of [³H]norepinephrine and [³H]tyrosine into the P₂ fraction was significantly inhibited by BWSV pretreatment. However, the effect of the venom on the uptake of [³H]deoxyglucose was slight. In addition, the venom-induced release of [³H]norepinephrine was much higher than that of [³H]deoxyglucose. The change in membrane potential of the preparation in duced by BWSV as examined using the voltage-sensitive fluorescence probe, 3, 3′-dipentyl-2, 2′-oxacarbocyanine. BWSV pretreatment markedly increased the synaptosomal fluorescence, indicating a depolarization of the preparation. This action of the venom was also observed in a Ca²⁺ -free or K⁺ -free medium, but could be blocked by pretreatment with antivenom. Pretreatment of the P₂ fraction with concanavalin A completely blocked the action of BWSV. Also, the BWSV failed to promote the release of transmitter if the venom was prein-cubated with a low concentration of purified gangliosides. Even after prolonged treatment with high concentrations of BWSV, an electron microscopic study showed no depletion of the synaptic vesicles in presynaptic terminals of the cortical P₂ preparations or striatal slices. It is suggested that the venom expresses its activity by binding to glycoproteins and/or gangliosides on the synaptic membrane, opening a cation channel. The subsequent depolarization then inhibits uptake processes and promotes transmitter release that is independent of external calcium.     

Morphology and physiology of peripheral giant interneurons in the forelegs (whips) of the whip spider Heterophrynus elaphus Pocock (Arachnida: Amblypygi)

Summary The tarsi of the modified front legs (whips) of the whip spider Heterophrynus elaphus contain two afferent giant fibers, GN1 and GN2, with diameters at the tibia-tarsus joint of ca. 21 m and 14 m, respectively. The somata of these two neurons lie in the periphery, about 25 cm away from the CNS. These two neurons are interneurons which receive mechanoreceptive inputs from approximately 750 and 1500 bristles, respectively. The receptive fields of GN1 and GN2 overlap; they extend for 40 mm (GN1) and 90 mm (GN2) along the length of the tarsus. About 90% of the synapses onto the giant fibers are axo-axonic. Mechanical stimulation of a single bristle is sufficient to elicit action potentials in one or both interneurons. The response of the interneurons adapts quickly. Average conduction time from the soma to the CNS is 45 ms for GN1 and 55 ms for GN2. Mean conduction velocities are 5.5 and 4.2 m/s, respectively. Activity in the giant fibers does not elicit a motor response; hence the giant fibers do not mediate an escape response. Possible functions of these giant fibers are discussed and compared to those of giant fiber systems in other arthropods.Abbreviations GN giant neuron - S segment     

Predation of Galendromus helveolus (Acari: Phytoseiidae) on Brevipalpus californicus (Acari: Tenuipalpidae)

The false spider mite, Brevipalpus californicus (Banks), is a major citrus pest in Texas. This phytophagous mite causes damage to fruit, leaves and stems of citrus, and is also a vector of citrus leprosis virus. Galendromus helveolus (Chant) is one of the most prevalent predacious mite species found on Texas citrus. The predation potential of G. helveolus on different stages of B. californicus was evaluated in the laboratory. An individual immature G. helveolus mite consumed an average of 30.7 eggs, 53.6 larvae, or 22.7 nymphs of B. californicus before developing to an adult. An individual adult female G. helveolus consumed an average of 164.8 eggs, 369.6 larvae, or 80.9 nymphs of B. californicus. Both immature and adult G. helveolus never fed on adult stage of B. californicus and never completed development. The development times of the immature stages of G. helveolus were 4.5, 4.1 and 4.6 days when fed on eggs, larvae and nymphs of B. californicus, respectively. When G. helveolus fed on the larval stage of B. californicus, the adults had the longest longevity (18.5 days) and the highest fecundity (14.0 eggs/female).     

虎纹捕鸟蛛毒素-I单残基突变体R20A-HWTX-I的化学合成与性质分析

虎纹捕鸟蛛毒素－１（Ｈｕｗｅｔｏｘｉｎ－１,ＨＷＴＸ－１）是从虎纹捕乌蛛（Ｓｅｌｅｎｏｃｏｓｍｉａ ｈｕｗｅｎａ）的粗只同的一种多肽类神经毒素。为了探明该毒素分子中统一的Ａｒｇ残基与其生物学活性的关系,运用固相多肽合成技术和Ｆｍｏｃ化学直接构建了Ａｌａ取代ＨＷＴＸ－１第２０位Ａｒｇ（Ｒ２０）的突变体Ｒ２０Ａ－ＨＷＴＸ－１;将合成的突一置于含谷胱甘肽的缓冲体系中氧化复性后用反相和特殊设计的离子交换Ｈ     

Prey Luring Coloration of A Nocturnal Semi‐Aquatic Predator

Body coloration serves a variety of purposes in animals. Diurnal and nocturnal predators such as spiders may use their body coloration to lure prey. We predicted here that the white patches on the forelegs on females of the nocturnal semi‐aquatic spider Dolomedes raptor lure prey, explaining why they are primarily displayed when the spider forages along the water edge. To test our prediction, we developed a color vision model assessing whether the patches are visible to pygmy grasshoppers, the spider's primary prey. We conducted a field experiment using cardboard dummies that resemble D. raptor in size, shape, and color, but with half of them lacking leg patches, and we staged interactions between pygmy grasshoppers and D. raptor with and without leg patches in a greenhouse. We found the white patches to be visible to grasshoppers. The dummies with white patches attracted more grasshopper prey than the dummies without the patches. Moreover, grasshoppers were more attracted to spiders when their white patches were present. Our results supported the hypothesis that the white patches of D. raptor lure prey. Our findings, nevertheless, could not be explained as the spider's body coloration acting as a sensory trap but it should not be ruled out. More studies on a wider range of predators and prey will give more meaningful insights into the co‐evolution of predatory lures and prey sensory modalities.