昆虫足的吸附机制

自然界中有许多昆虫足上都有吸附垫,这些垫子经过进化能吸附在各种表面上,并能在运动中控制吸附力。昆虫吸附垫要么是光滑的表皮垫子,要么是密布特殊的刚毛。昆虫这种“飞檐走壁”的能力来自于粘液、复杂机械系统以及生物系统之间的相互作用。文章主要参考国内外研究昆虫吸附机制的文献,综述了能在光滑表面上行走的昆虫的基本爬行原理,对其吸附机制进行了分类。并分析目前研究的主要内容,提出目前昆虫吸附机制要解决的问题。最后对吸附机制在仿生机械应用上作了展望。     

昆虫足的附着机制

昆虫卓越的爬行和附着能力来源于其精细的功能性黏附系统。根据形态结构的不同,昆虫的黏附系统可分为光滑型黏附垫和刚毛型黏附垫两种类型,二者在分泌液的支持下均能附着于几乎所有的光滑或粗糙的物体表面,而且这两种类型的黏附垫与界面的附着的形成均主要依赖于范德华力。本文综述了昆虫足的附着机制,包括光滑型和刚毛型两种黏附垫的结构和其形成附着的机理,以及黏附垫分泌液的功能、组成成分和释放机制,阐明了昆虫如何巧妙地解决稳定附着和快速脱附这一矛盾的问题,讨论了诸如界面的理化性质和环境湿度等环境因素对昆虫附着的影响,以期帮助人们深入地理解昆虫足的附着机制,并为其在仿生学等方面的应用提供理论依据。     

Evolution of insect pollination and angiosperm diversification

Insect pollination is a prominent type of plant-insect mutualism that can provide clues to the nature of diffuse coevolution. A long-standing question in this field is to what extent the emergence of insect polination caused rapid diversification in the interacting organisms. Recent progress in systematics and paleontology is providing much of the information needed to address this issue.     

SYMMETREE: whole-tree analysis of differential diversification rates

SymmeTREE implements several tests of differential diversification rates that exploit information on the topological distribution of species diversity throughout entire trees to address two general questions: (1) Has a given tree experienced significant variation in diversification rates among its branches? and (2) If so, along which branches have significant shifts in diversification rate occurred? These explicitly model-based methods are robust to uncertainty in estimates of branch length/duration and can accommodate incompletely resolved trees and other forms of phylogenetic uncertainty. AVAILABILITY: http://www.phylodiversity.net/bmoore/software.html CONTACT: brian.moore@yale.edu.     

Heart rate changes caused by varying the oxygen supply to isolated hind legs of rats

In a rat with an isolated hind leg circulation perfused with varying tyrode solutions, heart rate (HR) changes were studied in dependence of VO2 in the isolated hind leg and of PCO2, [K+], pH and lactic acid concentration ([Lac]) measured in the venous outflow of the isolated hind leg. In experimental series I the inflow PO2 (PiO2) was kept constantly high (either about 65 or 72 kPa). The perfusion pressure alternated between 16 and 24 kPa leading to flow rates in isolated hind legs (Qa) from 30 to 50 ml . 100 g-1 . min-1. The VO2 depended on the momentary Qa (flow-limited oxygen uptake). The [K+] and [Lac], the pH and the AVDO2 remained nearly constant while the PCO2 was lower at small flow rates. The HR decreases some 4 min after initial enhancement of Qa and VO2. Series II comprised experiments with low flow rates and a medium oxygen supply (Qa = 2.5-17.4 ml . 100 g-1 . min-1), PiO2 = 17.5-62.7 kPa). The VO2 ranged between 0.02 and 0.2 ml . 100 g-1 . min-1. The [K+] and [Lac], the PCO2 and the HR increased while the pH decreased. The [Lac] in the outflow showed a strong dependence on oxygen uptake and--at a weak oxygen supply--on the time. Cross-correlation analyses between the parameters confirmed that the HR was best temporally correlated to the [Lac] in the outflow.(ABSTRACT TRUNCATED AT 250 WORDS)     

Functional morphology of the hind legs as weapons for male contests inLeptoglossus australis (Heteroptera: Coreidae)

Functional morphology of the hind legs as weapons in male contests was analyzed in the leaf-footed plant bug, Leptoglossus australis Fabricius. Measurement of some metrical tratis of the hind femur and tibia indicated that the weapon was the hind femur. Sexual dimorphism in the femoral length and width, and in the number of spines on the lower side of the femur, indicated that these parts play a significant role in male contests. It was also suggested that the length from the base to the widest part of the femur had a functional significance for male-male combat behaviors ofL. australis.     

Host plant associations and geography interact to shape diversification in a specialist insect herbivore

Disentangling the processes underlying geographic and environmental patterns of biodiversity challenges biologists as such patterns emerge from eco‐evolutionary processes confounded by spatial autocorrelation among sample units. The herbivorous insect, Belonocnema treatae (Hymenoptera: Cynipidae), exhibits regional specialization on three plant species whose geographic distributions range from sympatry through allopatry across the southern United States. Using range‐wide sampling spanning the geographic ranges of the three host plants and genotyping‐by‐sequencing of 1,217 individuals, we tested whether this insect herbivore exhibited host plant‐associated genomic differentiation while controlling for spatial autocorrelation among the 58 sample sites. Population genomic structure based on 40,699 SNPs was evaluated using the hierarchical Bayesian model entropy to assign individuals to genetic clusters and estimate admixture proportions. To control for spatial autocorrelation, distance‐based Moran's eigenvector mapping was used to construct regression variables summarizing spatial structure inherent among sample sites. Distance‐based redundancy analysis (dbRDA) incorporating the spatial variables was then applied to partition host plant‐associated differentiation (HAD) from spatial autocorrelation. By combining entropy and dbRDA to analyse SNP data, we unveiled a complex mosaic of highly structured differentiation within and among gall‐former populations finding evidence that geography, HAD and spatial autocorrelation all play significant roles in explaining patterns of genomic differentiation in B. treatae. While dbRDA confirmed host association as a significant predictor of patterns of genomic variation, spatial autocorrelation among sites explained the largest proportion of variation. Our results demonstrate the value of combining dbRDA with hierarchical structural analyses to partition spatial/environmental patterns of genomic variation.     

Coordination between terminal variation of the viral genome and insect microRNAs regulates rice stripe virus replication in insect vectors

Maintenance of a balance between the levels of viral replication and selective pressure from the immune systems of insect vectors is one of the prerequisites for efficient transmission of insect-borne propagative phytoviruses. The mechanism regulating the adaptation of RNA viruses to insect vectors by genomic variation remains unknown. Our previous study demonstrated an extension of the 3’-untranslated terminal region (UTR) of two genomic segments of rice stripe virus (RSV). In the present study, a reverse genetic system for RSV in human cells and an insect vector, the small brown planthopper Laodelphax striatellus, was used to demonstrate that the 3’-terminal extensions suppressed viral replication in vector insects by inhibiting promoter activity due to structural interference with the panhandle structure formed by viral 3’- and 5’-UTRs. The extension sequence in the viral RNA1 segment was targeted by an endogenous insect microRNA, miR-263a, which decreased the inhibitory effect of the extension sequence on viral promoter activity. Surprisingly, the expression of miR-263a was negatively regulated by RSV infection. This elaborate coordination between terminal variation of the viral genome and endogenous insect microRNAs controls RSV replication in planthopper, thus reflecting a distinct strategy of adaptation of phytoviruses to insect vectors.