Mammalian Exocrine Secretions. XII: Constituents of Interdigital Secretions of Bontebok, Damaliscus dorcas dorcas, and Blesbok, D. d. phillipsi

In addition to the nine compounds identified in the interdigital secretion of the bontebok, Damaliscus dorcas dorcas, in a previous study, 76 compounds belonging to different compound types, were identified in the interdigital secretions of the bontebok and the blesbok, D. d. phillipsi. These compounds include alkanes, alcohols, aldehydes, ketones, fatty acids, terpenoids, -lactones, an isopropyl ester, long-chain hydroxyesters, 2-substituted pyridines, phenols, steroids, and dimethylsulfone. No qualitative differences were found between secretions from the two sexes or from animals from different habitats. Although no attempt was made to correlate territorial behavior or other behavioral phenomena with the qualitative composition of interdigital secretions from individual animals, available information seems to indicate that quantitative differences probably do not have a major semiochemical function. Only two species of bacteria, Bacillus brevis and Planococcus citreus, were found in the interdigital pouches of male and female members of the two subspecies, regardless of the habitat of the animals. B. brevis synthesized, among other unidentified constituents, (Z)-3-penten-2-ol, 2-hexanone, 2-octanone, 2-nonanone, tetradecanoic acid, pentadecanoic acid, heptadecanoic acid, octadecanoic acid, (Z)-9-hexadecenoic acid, and isopropyl hexadecanoate in vitro, while P. citreus produced, among others, the -lactones dodecan-4-olide and (Z)-6-dodecen-4-olide, which is one of the major constituents of the interdigital secretions of both subspecies. Some components of the interdigital secretions are not present in the interdigital glandular tissue, and the possibility is discused that these compounds could be produced by microbiological activity in the interdigital pouch.     

GENOMIC HARDWIRING AND PHENOTYPIC PLASTICITY OF TERPENOID-BASED DEFENSES IN CONIFERS

Over evolutionary history, conifers have faced a myriad of threats from phloem- and xylem-feeding insects, defoliating insects, and fungal pathogens. Among the trees defenses, terpenoids appear to play a major role by harming, disabling, deterring, repelling, or otherwise reducing the fitness of potential invaders. Each of the three classes of terpenoids in conifers, monoterpenes, sesquiterpenes, and diterpenes, are composed of a large number of representative compounds. In most cases, the presence of a particular terpenoid compound in the oleoresin or volatile emissions from a specific conifer can be accounted for by the expression of one of many committed terpene synthase (TPS) genes. However, while each TPS may produce one or a few major products, many produce a variety of minor products with relatively constant component ratios in the product blends. TPS genes exist in conifers in large and functionally diverse, yet monophyletic, gene families. Within these gene families, new biochemical functions of TPS appear to have evolved by gene duplication and changes in the amino acid sequence of the enzymes active site. In addition, TPS genes may be differentially expressed prior to, during, and following attack by insects or pathogens. Thus, while the production of any particular terpenoid is hardwired into a conifers genome, these trees have the capacity to change the mixture of terpenoids in oleoresin secretions and volatile emissions. Anatomical changes may also accompany induced terpenoid production, supplementing the plasticity of the molecular and biochemical events.     

Male Urinary Chemosignals Differentially Affect Aggressive Behavior in Male Mice

Chemical signals modulate aggressive behavior in mice. For example, male urinary cues enhance aggression against other adults: a resident mouse attacks a male but not a castrated intruder, unless it is anointed with male urine. Our purpose was to understand whether molecules excreted with urine also act as aggression triggers in a different context. Therefore, the effect of urine, or molecules purified from urine, voided by different animals (males or females), was tested on the aggression of male mice against pups. Latency to the first attack, percentage of pups receiving the first attack, and percentage of attacked pups after 5 and 15 min were recorded. At variance with intermale aggression, male urinary chemosignals sprayed on pups reduced infanticide, while female urine did not. Male urine also delayed infanticide when compared to female urine. Pups anointed with low molecular weight dialyzed urine and with the high molecular weight protein fraction were attacked later than controls. Pups anointed with Major Urinary Proteins (MUPs) also were attacked later. The volatiles retained by MUPs act in the same way as adult male urine. MUPs and their ligands did not modify biting of food items. The results show that mice do not perceive male chemosignals as compulsory aggression triggers but rather can consistently and differentially shape their behavior in response to the same molecules according to different contextual events.     

Acquired and Partially De Novo Synthesized Pyrrolizidine Alkaloids in Two Polyphagous Arctiids and the Alkaloid Profiles of Their Larval Food-Plants

The profiles of pyrrolizidine alkaloids (PAs) in the two highly polyphagous arctiids Estigmene acrea and Grammia geneura and their potential PA sources in southeastern Arizona were compiled. One of four species of Boraginaceae, Plagiobothrys arizonicus, contained PAs; this is the first PA record for this plant species. The principle PA sources are Senecio longilobus (Asteraceae) and Crotalaria pumila (Fabaceae). The known PA pattern of S. longilobus was extended; the species was found to contain six closely related PAs of the senecionine type. Three novel PAs of the monocrotaline type, named pumilines A-C, were isolated and characterized from C. pumila, a species not studied before. The pumilines are the major PAs in the seeds, while in the vegetative organs they are accompanied by the simple necine derivatives supinidine and as the dominant compound subulacine (1beta,2beta-epoxytrachelanthamidine). In both plant species, the PAs are stored as N-oxides, except C. pumila seeds, which accumulate the free bases. Great variation in PA composition was observed between local populations of C. pumila. The PA profiles were established for larvae and adults of E. acrea that as larvae had fed on an artificial diet supplemented with crotalaria-powder and of G. geneura fed with S. longilobus. In both experiments, the larvae had a free choice between the respective PA source and diet or food plants free of PAs. The profiles compiled for the two species reflect the alkaloid profiles of their PA sources with one exception, subulacine could never be detected in E. acrea. Besides acquired PAs, insect PAs synthesized from acquired necine bases and necic acids of insect origin were detected in the two arctiid species. These insect PAs that do not occur in the larval food sources accounted for some 40-70% (E. acrea) and 17-37% (G. geneura) of total PAs extracted from the insects. A number of novel insect PAs were identified. Plant-acquired and insect PAs were found to accumulate as N-oxides. The results are discussed in relation to specific biochemical, electrophysiological, and behavioral mechanisms involved in PA sequestration by arctiids.     

Detection and Discrimination of Conspecific Scents by the Anguid Slow-Worm Anguis fragilis

We tested the ability of male slow-worms, Anguis fragilis, a limbless anguid lizard with secretive, semifossorial habits, to detect chemical associated with conspecifics by using a T-maze in the laboratory. Male slow-worms discriminated conspecific male and female scent deposits. Males selected the arm with female scent, suggesting that scent deposits may be used to locate potential mates. Also, male slow-worms did not avoid the chemicals of other males, suggesting that they are not territorial. However, males discriminated their own scent from those of other males, and spent more time exploring the arm with other male scent, which suggests that scent marks may bear information that could be used in future intrasexual social contexts. We conclude that discrimination of conspecifics based on scents may be more widespread than previously expected among lizards inhabiting visually restricted environments.     

Phloeophagous and predaceous insects responding to synthetic pheromones of bark beetles inhabiting white spruce stands in the Great Lakes region

Tree killing and saprophytic bark beetles exert important ecological and economic roles in North American spruce forests. Chemical signaling among bark beetles, and responses by associate insects such as predators and competitors, have significant effects on the population dynamics and ecology of this community. Synthetic pheromones of primary (tree killing) and secondary (saprophytic) bark beetle species and blank controls were tested using multiple funnel and lower stem flight traps in white spruce forests in Wisconsin, Michigan, and Minnesota. Six phloeophagous and four predaceous species were collected with significant attraction by the bark beetles Dryocoetes affaber, Dryocoetes autographus, and Polygraphus rufipennis, and the predatory checkered beetles (Coleoptera: Cleridae) Thanasimus dubius and Enoclerus nigrifrons. In general, trap catches to synthetic lures resembled the species composition obtained by felling trees and collecting emerging beetles in a companion study, although several species showed differing trends. Some cross attraction occurred among bark beetles and between bark beetles and predatory beetles. For example, P. rufipennis was abundant in traps baited with Dryocoetes spp. pheromones. Thanasimus dubius and E. nigrifrons were collected in significant numbers in traps baited with the pheromone of the spruce beetle (Dendroctonus rufipennis), frontalin plus -pinene. This is a new observation for E. nigrifrons. Attraction of T. dubius to the pheromones of at least three bark beetle species in the Great Lakes region, as well as to several southern and western species, reflects its role as a habitat specialist and feeding generalist. Several other important predators and competitors commonly obtained in pine forests in this region were not obtained in these spruce stands, either in response to synthetic pheromones of spruce colonizing beetles, or in host material colonized by these beetles. Potential differences in predator prey dynamics between spruce and pine ecosystems in the Great Lakes region are discussed.     

Differences in host use efficiency of larvae of a generalist moth, Operophtera brumata on three chemically divergent Salix species

The food selection, growth, and fecundity of insect herbivores are largely dictated by the chemical composition and nutritive values of plant foliage. We studied the host-use efficiency of larvae of the generalist moth, Operophtera brumata (Lepidoptera: Geometridae) on three chemically divergent but nutritively similar willows (Salix spp.). The 4th instars were able to use the salicylate-free leaves of S. phylicifolia efficiently. Growth was slightly reduced on S. pentandra, which contained a moderate level of acetylated salicylates. The high concentration of salicylates found in the leaves of S. myrsinifolia seemed to provide efficient protection against non-specialized O. brumata. We also studied assimilation of nutrients and degradation of salicylates and other secondary compounds in the digestive tract of O. brumata larvae. Neither the assimilation of nitrogen nor of carbon were affected by secondary chemicals of ingested food. Salicylates were shown to be degraded to salicin and catechol, while further degradation of salicin to saligenin was rather slow. In an artificial diet experiment, we showed that two degradation products of salicylates, catechol and saligenin markedly reduced the growth of the larvae. Neither salicin nor chlorogenic acid affected larval growth. We conclude that salicylates reduced the growth of the generalist winter moth mainly by feeding deterrence caused by 6-hydroxy-2-cyclohexenone and catechol. Compared to the deleterious effects of salicylates the effects of other secondary compounds were minor.     

基于多级推理的玉米病虫害专家系统

详细介绍了玉米病虫害专家系统的设计与开发,包括数据库,知识库以及推理机的设计,针对玉米病虫害多样性增加导致传统的专家系统诊断时出现的同一症状对应多个诊断结果的粗糙诊断问题,提出基于多级推理的玉米病虫害专家系统,根据玉米的发病症状,在病虫害的可能性中进行综合判断,以发病时期,发病条件,发病部位为依据采用多级推理机制,以降低推理结果集元素的数量,同时可视知识参与推理,为推理提供感观信息,提高推理的准确性。     

基于二维广义Logistic映射的图像加密算法

提出一个基于广义Logistic方程构造的二维混沌映射,采用Feigenbaum常数、相图、分岔图分析的方法,研究该混沌映射的非线性动态特性;然后利用该方程生成混沌序列,将混沌序列进行优化改进,生成密钥序列;最后采用输出反馈的加密方式,改变图像的像素值,达到加密的目的。实验仿真表明,该加密算法对密钥非常敏感,有效地提高了抵御选择明文攻击的能力,密文图像信息熵为7.996 94,非常接近理想值8。加密图像像素值具有类随机均匀分布特性,加密图像和明文图像之间的相关性非常接近于0,相邻像素具有零相关特性,而且密钥空间达到299比特。加密方法大大改变了明文图像的像素值,使得密文能够抵御统计攻击。     

昆虫飞行高升力机理的研究

随着仿生扑翼飞行机器人的微型化,当扑翼飞行机器人达到昆虫量级的时候,任何复杂的运动系统都将面临难以实现的问题.本文从研究现有比较成熟的昆虫飞行高升力机制出发,指出了现有"昆虫飞行高升力机理"研究成果中存在的一些问题,用"柔性楔形效应"对昆虫飞行高升力机理进行了合理解释,提出"柔性楔形效应"是昆虫前飞过程中获得很大升力的主要原因.用"柔性楔形效应"解释昆虫飞行高升力机理,翅翼运动的模拟方式有可能只需在自适应变形状态下施以简单的节律运动.该结论将对仿生扑翼飞行机器人的研究产生重要影响.