Changes in the mechanical properties of the extensible cuticle of Rhodnius through the fifth larval instar

The ultimate tensile strength (σ_UT) and the modulus of elasticity (E) of Rhodnius extensible cuticle are σ_UT = 2.20 × 10⁷ Nm^?2, E = 2.43 × 10⁸ Nm^?2 (unplasticised); σ_UT = 1.43 × 10⁷ Nm^?2, E = 9.45 × 10⁶ Nm^?2 (plasticised with 5HT) and σ_UT = 9.05 × 10⁶ Nm, E = 2.46 × 10⁶ Nm^?2 (plasticised in pH 5 buffer).The mechanical properties of cuticle from insects which have deposited additional layers of cuticle after they have been fed differ from those of cuticle from unfed insects. This is possibly due to the different composition of the additional cuticle: it is suggested that the post-feeding cuticle is providing protection and a template for the next instars cuticle.The maximum strain of extensible cuticle from starved insects is related to the amount of matrix protein present.     

植物角质膜及其渗透性与抗旱性研究进展

角质膜覆盖于陆生植物的地上部分,是植物与外部环境之间的第一道屏障,保护植物免遭各种生物和非生物胁迫。本文就植物角质膜的结构、成分、生物合成的途径及机理、渗透性及温度、湿度、活性剂对角质膜渗透性的影响,角质膜与植物抗旱性关系的研究进展做系统综述,并对植物角质膜研究中存在的问题进行了探讨。     

Water loss through the integument in the desiccation-sensitive mutant, Parched, of Drosophila melanogaster

Two desiccation-sensitive mutants of Drosophila melanogaster were isolated. Genetic analysis showed that the phenotype is controlled by a recessive gene parched located in 1A1-8 of the X-chromosome. In a desiccated environment without any water supply, the survival time of the mutant flies was considerably shorter than that of the wild-type flies. The rate of water loss in the mutant flies was significantly higher than that of the wild-type flies, whether dead or alive. The survival time of the mosaic flies, which have the mutant and wild-type cuticle, was prolonged in proportion to the amount of wild-type cuticle which they possessed. These results suggest that the mutant has a defect in some waterproofing mechanism of the integument. The mutant flies drank much more water than the wild-type flies, to compensate for the rapid water loss. The hydrocarbons, which are the predominant constituent of cuticular lipids, were analyzed by gas-liquid chromatography, but there were no significant quantitative nor qualitative differences between the wild-type and the mutant flies.     

Electron Microscope Studies on the Cuticle of Swarming and Nonswarming Tylenchorhynchus martini

Studies on the structure of the cuticle of Tylenchorhynchus martini swarmers with electron microscopes revealed abnormal disruptive and eruptive morphological changes in most layers. Drastic effects of swarming on cuticular structure were reflected in the partial dissolution of cortical layer and matrix and in the irregular cracking of cortical sublayers in sublateral areas of the body. The occurrence of projections in the cortex was apparently unrelated to other changes. The structure of the cuticle of nonswarmers was intact and without any morphological changes.     

植物角质蒸腾的几个方面

角质蒸腾速率和植物生态型有密切关系,与普通品种相比抗旱的高粱和玉米品种角质蒸腾较弱,或差异不明显,但节水途径不同。强光促进角质层腊质的形成,使角质蒸腾减弱。高湿度下生长的植物移到湿度较低处后,其角质蒸腾与总蒸腾速率都明显增大。土壤干旱对角质蒸腾的影响因植物种类和水分胁迫的具体情况而异。角质层腊质含量和角质蒸腾速率一般呈反相关。     

Adoption of lycaenid Niphanda fusca (Lepidoptera: Lycaenidae) caterpillars by the host ant Camponotus japonicus (Hymenoptera: Formicidae)

Caterpillars of the parasitic lycaenid butterfly are often adopted by host ants. It has been proposed that this adoption occurs because the caterpillars mimic the cuticular hydrocarbons of the host ant. This study aimed to examine whether caterpillars of the Japanese lycaenid butterfly Niphanda fusca induce adoption by mimicking their host ant Camponotus japonicus. Behavioral observations conducted in the laboratory showed that most second‐instar caterpillars were not adopted, whereas most third‐instar caterpillars were successfully adopted by host workers. A chemical comparison detected no characteristic differences in the cuticular hydrocarbon profiles between second‐ and third‐instar caterpillars. However, morphological features of the caterpillars differed between the second and third instars; third‐instar caterpillars developed exocrine glands (ant organs) such as tentacle organs and a dorsal nectary organ. These results suggest that multiple chemical signatures, not only cuticular hydrocarbons, may be important for invasion of the host ant nest.     

Co-permeability of 3H-labelled water and 14C-labelled organic acids across isolated Prunus laurocerasus cuticles: effect of temperature on cuticular paths of diffusion

Co‐permeability of ³H‐labelled water and ¹⁴C‐labelled benzoic acid or 2,4‐dichlorophenoxyacetic acid across isolated cuticular membranes of Prunus laurocerasus L. was measured at temperatures ranging from 15 to 50 °C. The water and benzoic acid permeances were highly correlated over the whole temperature range investigated, whereas water and 2,4‐dichlorophenoxyacetic acid permeances were only correlated between 15 and 30 °C. The activation energies of cuticular permeability calculated from Arrhenius plots were 40 kJ mol^?1 for water and benzoic acid and 115 kJ mol^?1 for 2,4‐dichlorophenoxyacetic acid. The slopes of the Arrhenius plots of 2,4‐dichlorophenoxyacetic acid were linear between 15 and 50 °C, whereas pronounced phase transitions around 30 °C were observed for water and benzoic acid permeability. However, with isolated polymer matrix membranes, where cuticular waxes forming the transport‐limiting barrier of cuticles have been extracted, phase transitions were not observed for water and benzoic acid. It is concluded that temperatures above 30 °C caused structural changes in the transport‐limiting barrier of the cuticles leading to additional paths of diffusion for water and benzoic acid but not for 2,4‐dichlorophenoxyacetic acid.     

The Guianese population of the fire ant Solenopsis saevissima is unicolonial

In this study, conducted in French Guiana, a part of the native range of the fire ant Solenopsis saevissima, we compared the cuticular hydrocarbon profiles of media workers with previous results based on intraspecific aggressiveness tests. We noted a strong congruence between the two studies permitting us to delimit 2 supercolonies extending over large distances (up to 54 km), a phenomenon known as unicoloniality. Solenopsis geminata workers, taken as an out‐group for cluster analyses, have a very different cuticular hydrocarbon profile. Because S. saevissima has been reported outside its native range, our conclusion is that this species has the potential to become invasive because unicoloniality (i.e., the main attribute for ants to become invasive) was shown at least for the Guianese population.     

昆虫表皮蛋白及其基因表达调控机理的研究进展

昆虫表皮蛋白(insectcuticular proteins,ICP)是结构蛋白,它和几丁质一起组成昆虫抵御外界环境的屏障——角质层。根据保守性基序的不同,ICP可分为CPR、CPF、CPFL、CPG和CPT5家族。它们都有独特的结构与性质。环境、激素、转录因子和内含子等共同影响昆虫表皮蛋白基因(insect cuticular protein genes,ICPG)的表达,进而使ICPG具有时期和组织特异性。ICP和ICPG被认为是研究昆虫蜕皮与变态的调控机理和理解昆虫发育期角质层在生物化学、物理化学以及结构上的修饰的重要模型,受到越来越多的重视。本文综述了ICP的分类以及环境、激素、转录因子和内含子等对ICPG表达的调控。     

叶表面角质层在贝母属植物叶鉴定中的意义

叶表面角质层在贝母属植物叶鉴定中的意义李萍，濮祖茂，蒋鑫，刘惠娟，徐国钧（中国药科大学生药学教研室；分析中心电镜室南京２１０００９）ＴｈｅｄｉａｇｎｏｓｔｉｃｖａｌｕｅｏｆｔｈｅｃｕｔｉｃｌｅｉｎｔｈｅｌｅａｖｅｓｆｒｏｍｇｅｎｕｓＦｒｉｔｉｌｌａｒ...     

The cuticular scales of Lynx spiders (Araneae,Oxyopidae)

An examination of the cuticular scales of the lynx spiders Oxyopes aglossus, O. salticus, and Peucetia viridans using scanning electron microscopy revealed that scales in these spiders are morphologically distinct, yet similar to the scales of the jumping spiders Eris militaris and Hentzia mitrata. Like the cuticular scales of jumping spiders, the cuticular scales of lynx spiders exhibit morphological differentiation in regard to location of occurrence on the body, with scales near the eyes tending to have more numerous and larger spines on the superior surface than scales on other regions of the prosoma and opisthosoma. The functional significance of this differentiation in scale morphology is unknown. Sexual dimorphism and ontogenetic variation in scale morphology and color were observed in the genus Oxyopes,but not in Peucetia. In addition, the scales of P. viridans were distinguishable from the scales of Oxyopes spp. on the basis of the number of apical spines (1 in P. viridans instead of 3–7 in Oxyopesspp.) and on the presence of spines on the inferior surface (many in P. viridans and none in Oxyopesspp.). J. Morphol. 236:223-231, 1998. © 1998 Wiley-Liss, Inc.     

Ontogenetic and seasonal development of wax composition and cuticular transpiration of ivy (Hedera helix L.) sun and shade leaves

The ontogenetic and seasonal development of wax composition and cuticular transpiration of sun and shade leaves of ivy (Hedera helix L.) was analysed by investigating leaves varying in age between 4 and 202 d. It was discovered that the total amount of solvent-extractable wax was composed of two distinct fractions, separable by column chromatography: (i) a less polar or apolar monomeric wax fraction consisting of the typical linear, long-chain aliphatics usually described as cuticular wax components and (ii) a polar, oligomeric wax fraction consisting of primary alcohols and acids mostly esterified to C₁₂-, C₁₄- and C₁₆-ω-hydroxyfatty acids. The apolar wax fraction, which could be analysed directly by gas chromatography coupled with mass spectrometry (GC-MS), exhibited pronounced seasonal changes in composition. Wax amounts in the apolar fraction reached a maximum after about 30 d and gradually decreased again during the remaining period of the season investigated. In contrast, the polar wax fraction, which was analysable by GC-MS only after transesterification, rapidly increased early in the season, reaching a plateau after 40 d, and then remained constant during the rest of the season. Thus, total amounts of solvent-extractable cuticular waxes, which can be determined gravimetrically, will only be detected by GC-MS after fractionation and transesterification, a methodological approach rarely applied in the past in cuticular wax analysis. Additionally, investigation of the cutin polymer matrix after depolymerisation through transesterification, revealed that only those primary alcohols and acids forming an essential part of the apolar and the polar wax fractions were esterified during the investigated season and incorporated in increasing amounts into the cutin polymer matrix (matrix-bound wax fraction). Thus, it can be concluded that a complete analysis of cuticular wax of ivy and its seasonal development can only be achieved if all the relevant fractions (i) the less polar or apolar, (ii) the polar and (iii) the wax fraction bound to the cutin polymer matrix are investigated. Cuticular transpiration rapidly decreased within the first 30 d and essentially remained constant during the rest of the season. Thus, changes in cuticular water permeability were closely correlated with the most prominent changes in wax amounts and composition occurring during the first 30 d of ontogenetic leaf development. However, during the remainder of the year, up to 202 d, cuticular transport properties remained constant, although significant quantitative and qualitative changes in cuticular wax composition continued to occur. Thus, our study clearly demonstrated that there will be no simple relationship between chemical composition of cuticular waxes and transport properties of isolated ivy leaf cuticles. Received: 2 March 1998 / Accepted: 26 June 1998     

Stomatal behaviour and cuticular properties of maize leaves of different chilling-resistance during cold treatment

Stomatal behaviour and the amount and synthesis of epicuticular waxes were studied in maize leaves of various degrees of chilling resistance in order to investigate the rapid desiccation characteristic of chilling injury. In contrast to the resistant variety (KSC 360), the sensitive line (Lye) failed to close the stomata during chilling treatment. Both, the amount of epicuticular waxes and their degree of labeling by 1-14C-acetate were much higher in the resistant than in the sensitive leaves. Chilling-sensitivity was also related to a suppressed conversion of free fatty acids into free primary alcohols.     

The evolution of queen pheromones in the ant genus Lasius

Queen pheromones are among the most important chemical messages regulating insect societies yet they remain largely undiscovered, hindering research into interesting proximate and ultimate questions. Identifying queen pheromones in multiple species would give new insight into the selective pressures and evolutionary constraints acting on these ubiquitous signals. Here, we present experimental and comparative evidence that 3‐methylalkanes, hydrocarbons present on the queen's cuticle, are a queen pheromone throughout the ant genus Lasius. Interspecific variation in the chemical profile is consistent with 3‐methylalkanes evolving more slowly than other types of hydrocarbons, perhaps due to differential selection or evolutionary constraints. We argue that the sensory ecology of the worker response imposes strong stabilizing selection on queen pheromones relative to other hydrocarbons. 3‐Methylalkanes are also strongly physiologically and genetically coupled with fecundity in at least one Lasius species, which may translate into evolutionary constraints. Our results highlight how honest signalling could minimize evolutionary conflict over reproduction, promoting the evolution and maintenance of eusociality.     

Cuticular hydrocarbon profiles as a taxonomic tool: advantages,limitations and technical aspects

Cuticular hydrocarbons (CHCs) are expressed on an insect's cuticle and are one of the major factors allowing insects to identify members of their own species, colony and gender. As a result of their species‐specificity, CHCs are increasingly used to delimit species in addition to more conventional methods, such as morphology or genetic markers, and so play an important role in chemotaxonomy. Species vary in the type of CHCs that they produce, as well as in the relative quantities of shared compounds. This review summarizes not only how taxonomists may differentiate between species based on CHC profiles, but also the incentive for using CHC composition as taxonomic tool. Benefits regarding the identification of cryptic species and early signs of reproductive isolation are then discussed, giving examples from studies of taxonomy, behaviour and biosynthesis. For taxonomic characters to reliably indicate species boundaries, their limitations need to be known. Potential problems caused by environmental effects, intra‐species variation in profiles and other technical issues are highlighted, and suggestions are made regarding their avoidance. It remains a challenge to determine the variation beyond which two species can be called independent; a problem shared by most methods of delimitation. Recently, there has been a shift towards using a combination of different taxonomic tools, both molecular and non‐molecular, to test observed species differences.     

Biosynthesis of contact sex pheromone in the female tsetse fly, Glossina morsitans morsitans Westwood

Injection of [2,3 ¹⁴C] sodium succinate into recently emerged, unfed females of Glossina morsitans morsitans resulted in incorporation of radiolabel mainly into surface cuticular alkanes. In vivo experiments with intact flies showed that the distribution of labelled alkanes depended on fly mobility, the legs of unrestrained flies possessing proportionately larger amounts of radioactive hydrocarbon material than those of flies whose legs were tied together with a silk suture. The heads of both restrained and unrestrained flies contained proportionately more material per unit surface area than did any other body part. However, ablation experiments and in vitro incubation showed that the most active incorporation of label into alkanes occurred in the abdomen and that all dorsal abdominal segments were equally active. The ventral abdomen also incorporated label into cuticular alkanes in vitro, but other body parts were apparently less able to do so. The sex pheromone of G. m. morsitans is a trimethyl-substituted alkane, the labelling of which appeared to be in proportion to the relative abundance of its methyl groups among those of the other alkanes of the cuticle following injection of either intact or legless flies. Hence it is proposed that sex pheromone is synthesized along with other cuticular alkanes mainly by cells closely associated with the abdominal cuticle of females and that it is spread over the external surface both by diffusion and by grooming which leads to accumulations of hydrocarbon material on the legs.