The potential role of phoresy in the evolution of parasitism: radiolabelling (tritium) evidence from an astigmatid mite

Using tritium as a radiolabel marker of interspecific fluid transfer, we present experimental evidence that the heteromorphic deutonymph of an astigmatid mite (Hemisarcoptes cooremani) acquires materials (at least water) directly from the haemolymph of its beetle host (Chilocorus cacti). This acquisition is above that obtained from atmospheric vapour. The material acquired from the host is necessary for the completion of the ontogeny of H. cooremani and is likely procured through the action of the caudal ventral suckers of the heteromorphic deutonymph (hypopus). On gross morphological criteria, this mite-beetle relationship was previously defined as phoretic (for dispersal). Scanning electron photomicrographs of the physical relationship between the hypopodes and the heetles shed light on the parasitic nature of the hypopus of H. cooremani. Our findings are discussed in terms of the evolution of parasitism from a free-living astigmatid form. This transition into parasitism is facilitated by the heteromorphic hypopus and represents a classic wolf-insheep's-clothing strategy. The heteromorph retains the characteristic phoretic morphology while exploiting the host in transit.     

Combined versus Single Species Release of Predaceous Mites: Predator–Predator Interactions and Pest Suppression

Interactions such as competition, intraguild predation (IGP), and cannibalism affect the development and coexistence of predator populations and can have significance for biological control of commonly exploited pest organisms. We studied the consequences of combined versus single release of two predaceous mite species (Phytoseiidae), with differing degrees of diet specialization, on their population dynamics and the suppression of the carmine spider mite, Tetranychus cinnabarinus Boisduval (Tetranychidae), on greenhouse-grown gerbera. Population growth of the specialist predator Phytoseiulus persimilis Athias-Henriot was greater and population decline steeper when released in combination with the generalist Neoseiulus californicus McGregor than when released alone. In contrast, the N. californicus population grew and declined more gradually when released in combination with P. persimilis, compared to the single species release. The differential impact on each other's population dynamics can be primarily attributed to contrasting properties in competition, IGP, and cannibalism. At the same overall predator density and as long as prey was abundant, the specialist P. persimilis was more strongly affected by intraspecific competition than by interspecific competition with the generalist N. californicus. In contrast, interspecific competition with P. persimilis had a greater impact on N. californicus than intraspecific competition. After prey depletion, the generalist predator N. californicus was more likely to engage in IGP than was the specialist predator P. persimilis. Overall, the study demonstrates that prey specificity has significance for the quality and intensity of predator–predator interactions and indicates potential implications for biological control of spider mites. All predator releases (i.e., either species alone and both species in combination) resulted in reduction of the spider mite population to zero density. Individual release of the specialist P. persimilis led to the most rapid spider mite suppression. Nonetheless, in perennial greenhouse-grown crops P. persimilis and N. californicus could have complementary effects and a combination of the two predators could enhance long-term biological control of spider mites. The potential risks and benefits associated with the release of both species are discussed.     

DNA标记技术在螨类系统学研究中的应用

长期以来,螨类主要依靠其形态特征进行系统学研究。DNA标记是指能反映生物个体或物种间基因组中某种差异特征的DNA片段。近年来,DNA标记技术在螨类系统学研究中得到越来越广泛的应用。本文综述了随机扩增多态性RAPD、限制性内切酶片段长度多态性RFLP、微卫星SSR、核酸序列扩增、扩增片段长度多态性AFLP和直接扩增片段长度多态性DALP等6种DNA标记技术在螨类系统学研究中的应用现状及前景。     

田间植物对捕食螨的影响Ⅰ：猎物寄主植物的影响

捕食螨是重要的生物防治因子,影响捕食螨发挥生物防治效果的因素很多,猎物寄主植物在捕食螨的产卵、取食定位等行为活动中起着重要作用。本文主要从化学生态学、形态结构和植物营养的角度综合分析了植物自身释放的挥发物、植物受机械损伤后释放的挥发物和植物受猎物为害后释放的挥发物对捕食螨的取食定位影响,猎物寄主植物形态结构以及猎物寄主植物花粉和汁液等营养物作为捕食螨的替代食物对捕食螨的影响,同时阐述其研究趋势和前景。     

Host preference by Allothrombium pulvinum (Acari: Trombidiidae) larvae on aphids: Macrosiphum rosae,Aphis gossypii and Hyalopterus amygdali (Homoptera: Aphididae)

In this study aphid-plant association and its effect on host preference of parasitic Allothrombium pulvinum larvae was examined with multiple-choice tests. Host species selection, host size selection and superparasitism with mite larvae were studied with two-choice tests. Three aphid species were used: Macrosiphum rosae, Aphis gossypii and Hyalopterus amygdali. In multiple-choice tests, larvae of A. pulvinum showed no significant preference for any aphid-plant association when given M. rosae on rose, A. gossypii on cucumber and H. amygdali on apricot simultaneously. Two-choice tests showed that larval mites preferred H. amygdali to A. gossypii, but had no preference when offered a choice between A. gossypii and M. rosae or between H. amygdali and M. rosae. In host size selection and superparasitism tests, significantly more mites selected the larger host (M. rosae). Furthermore, parasitised H. amygdali were preferred to unparasitised ones. This revised version was published online in July 2006 with corrections to the Cover Date.     

Positive association between thrips and spider mites in seedling cotton

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食蚜绒螨对棉花苗蚜的控制作用研究

通过2年的田间调查和小区试验发现:(1)食蚜绒螨与被寄生的棉蚜有翅蚜和无翅蚜在时间—数量分布上具相似性。(2)棉蚜带螨率结果说明,50％有翅蚜可被迁入初期杀死,可使大部分棉蚜繁殖力下降或不能生殖;(3)棉田播种前施肥、浅翻,对食蚜绒螨的发生量不具明显影响;(4)食蚜螨在棉田期其他棉蚜天敌缺少的情况下,填补了此期控蚜天敌时间生态位的空缺,成为棉田生态系统中不可缺少的一员。     

Conflict between antipredator and antiparasite behaviour in larval damselflies

 Larval damselflies resist infestation by parasitic larval mites by exhibiting behaviours such as grooming, crawling, swimming, and striking at host-seeking mites. Larval damselflies are known to increase time spent in these behaviours in the presence of mites but reduce time spent in these behaviours in the presence of fish predators. The presence of both fish and larval mites presents an obvious conflict: a larval damselfly may actively avoid parasitism by mites, thus increasing its risk of predation, or it may reduce its activity when fish are present, thus increasing its risk of parasitism. We analysed the behaviour of larval Ischnura verticalis in an experiment where we crossed presence and absence of fish with presence and absence of larval mites. Presence of mites induced a large increase in activity of larval I. verticalis but fish had no effect and there were no interpretable interactions between effects of mites and fish. Subsequent experiments indicated that larval I. verticalis in the presence of both mites and fish were more likely to be attacked and killed by fish than those exposed only to fish. The high activity level of I. verticalis larvae in the presence of both fish and mites may suggest that costs of parasitism are high, or that under field conditions it is rare for larvae to be in the immediate presence of both fish predators and potentially parasitic mites. Received: 28 March 1996 / Accepted: 6 September 1996     

Low parasite loads accompany the invading population of the bumblebee, Bombus terrestris in Tasmania

In its native Europe, the bumblebee, Bombus terrestris (L.) has co-evolved with a large array of parasites whose numbers are negatively linked to the genetic diversity of the colony. In Tasmania B. terrestris was first detected in 1992 and has since spread over much of the state. In order to understand the bee’s invasive success and as part of a wider study into the genetic diversity of bumblebees across Tasmania, we screened bees for co-invasions of ectoparasitic and endoparasitic mites, nematodes and micro-organisms, and searched their nests for brood parasites. The only bee parasite detected was the relatively benign acarid mite Kuzinia laevis (Dujardin) whose numbers per bee did not vary according to region. Nests supported no brood parasites, but did contain the pollen-feeding life stages of K. laevis. Upon summer-autumn collected drones and queens, mites were present on over 80% of bees, averaged ca. 350–400 per bee and were more abundant on younger bees. Nest searching spring queens had similar mite numbers to those collected in summer-autumn but mite numbers dropped significantly once spring queens began foraging for pollen. The average number of mites per queen bee was over 30 fold greater than that reported in Europe. Mite incidence and mite numbers were significantly lower on worker bees than drones or queens, being present on just 51% of bees and averaging 38 mites per bee. Our reported incidence of worker bee parasitism by this mite is 5–50 times higher than reported in Europe. That only one parasite species co-invaded Tasmania supports the notion that a small number of queens founded the Tasmanian population. However, it is clearly evident that both the bee in the absence of parasites, and the mite have been extraordinarily successful invaders. Received 12 April 2006; revised 10 November 2006; accepted 15 November 2006.