Deciphering the Chemical Basis of Nestmate Recognition

Social insects maintain colony cohesion by recognizing and, if necessary, discriminating against conspecifics that are not part of the colony. This recognition ability is encoded by a complex mixture of cuticular hydrocarbons (CHCs), although it is largely unclear how social insects interpret such a multifaceted signal. CHC profiles often contain several series of homologous hydrocarbons, possessing the same methyl branch position but differing in chain length (e.g., 15-methyl-pentatriacontane, 15-methyl-heptatriacontane, 15-methyl-nonatriacontane). Recent studies have revealed that within species these homologs can occur in correlated concentrations. In such cases, single compounds may convey the same information as the homologs. In this study, we used behavioral bioassays to explore how social insects perceive and interpret different hydrocarbons. We tested the aggressive response of Argentine ants, Linepithema humile, toward nest-mate CHC profiles that were augmented with one of eight synthetic hydrocarbons that differed in branch position, chain length, or both. We found that Argentine ants showed similar levels of aggression toward nest-mate CHC profiles augmented with compounds that had the same branch position but differed in chain length. Conversely, Argentine ants displayed different levels of aggression toward nest-mate CHC profiles augmented with compounds that had different branch positions but the same chain length. While this was true in almost all cases, one CHC we tested elicited a greater aggressive response than its homologs. Interestingly, this was the only compound that did not occur naturally in correlated concentrations with its homologs in CHC profiles. Combined, these data suggest that CHCs of a homologous series elicit the same aggressive response because they convey the same information, rather than Argentine ants being unable to discriminate between different homologs. This study contributes to our understanding of the chemical basis of nestmate recognition by showing that, similar to spoken language, the chemical language of social insects contains “synonyms,” chemicals that differ in structure, but not meaning.     

The Chemical Basis of Host-Plant Recognition in a Specialized Bee Pollinator

Many pollinators specialize on a few plants as food sources and rely on flower scents to recognize their hosts. However, the specific compounds mediating this recognition are mostly unknown. We investigated the chemical basis of host location/recognition in the Campanula-specialist bee Chelostoma rapunculi using chemical, electrophysiological, and behavioral approaches. Our findings show that Ca. trachelium flowers emit a weak scent consisting of both widespread and rare (i.e., spiroacetals) volatiles. In electroantennographic analyses, the antennae of bees responded to aliphatics, terpenes, aromatics, and spiroacetals; however, the bioassays revealed a more complex response picture. Spiroacetals attracted host-naive bees, whereas spiroacetals together with aliphatics and terpenes were used for host finding by host-experienced bees. On the intrafloral level, different flower parts of Ca. trachelium showed differences in the absolute and relative amounts of scent, including spiroacetals. Scent from pollen-presenting flower parts elicited more feeding responses in host-naive bees as compared to a scentless control, whereas host-experienced bees responded more to the nectar-presenting parts. Our study demonstrates the occurrence of learning (i.e., change in the bee’s innate chemical search-image) after bees gain foraging experience on host flowers. We conclude that highly specific floral volatiles play a key role in host-flower recognition by this pollen-specialist bee, and discuss our findings into the broader context of host-recognition in oligolectic bees.     

Identification of Termite Species by the Hydrocarbons in their Feces

Blends of abundant cuticular hydrocarbons are species-specific for termites (Isoptera) and can be used to identify a given taxon without the diagnostic castes, soldiers or adults. We demonstrate that hydrocarbon extracts of termite fecal pellets from damaged wood can also be characterized and used to identify termites responsible for damage, even though termites are no longer present or easily recovered. In structures infested by drywood termites, it is common to find fecal pellets, but difficult to extract termites from the finished wood in service. Nine species belonging to two families (Kalotermitidae and Termopsidae) were examined to compare the hydrocarbon composition of termites and their fecal pellets. Diversity was extensive: at least one half of the amount of the hydrocarbons from Neotermes connexus, Incisitermes immigrans, Cryptotermes brevis, Cryptotermes cynocephalus, Procryptotermes corniceps, and Zootermopsis nevadensis nuttingi was olefins. Incisitermes minor and Pterotermes occidentis incorporated only small amounts of olefins in cuticular hydrocarbons; Marginitermes hubbardi had no detectable olefins. Hydrocarbons extracted from fecal pellets were qualitatively and quantitatively similar to cuticular extracts and can be used to determine the termite species responsible without the termites present.     

Learned Recognition of Predation Risk by Enallagma Damselfly Larvae (Odonata, Zygoptera) on the Basis of Chemical Cues

We studied two populations of damselfly larvae (Enallagma boreale): one population cooccurred with a predatory fish (northern pike, Esox lucius); the other did not. Damselflies that cooccurred with pike adopted antipredator behavior (reduced activity) in response to chemical stimuli from injured conspecifics, and to chemical stimuli from pike, relative to a distilled water control. Damselflies from an area where pike do not occur responded only to chemical stimuli from injured conspecifics. In a second set of experiments, we conditioned pike-naive damselflies to recognize and respond to chemical stimuli from pike with antipredator behavior. Damselfly larvae that were previously unresponsive to pike stimuli learned to recognize pike stimuli after a single exposure to stimuli from pike and injured damselflies or pike and injured fathead minnows (Pimephales promelas). The response to injured fathead minnows was not a general response to injured fish because damselfly larvae did not respond to chemical stimuli from injured swordtails (Xiphophorus helleri), an allopatric fish. Taken together, these data suggest a flexible learning program that allows damselfly larvae to rapidly acquire the ability to recognize local predation risk based on chemical stimuli from predators, conspecifics, and heterospecific members of their prey guild.     

《化工设备基础》课程改革与实践初探

按照“以就业为导向,以服务为宗旨”的职业教育目标,我们培养的学生应当具备良好的职业道德和职业素质,应当具有熟练的职业技能,走上职业岗位之后具备可持续发展的能力。如何培养学生具备这些能力,是通过课程体系的改革来实现的。本文详细阐述了《化工设备基础》课程改革的具体实施过程,得出改传统的教学方法为项目化教学方法,在《化工设备基础》课程教学中,效果是非常明显的。     

ANSYS在《化工设备机械基础》课程教学中的应用

《化工设备机械基础》是过程装备与控制工程专业一门重要的专业基础课,对学生今后从事过程装备的设计、计算、设备选型和应用工作有重要作用。在课程的化工容器设计教学阶段,结合ANSYS有限元软件进行辅助教学,通过几年来的教学实践表明,采用ANSYS软件进行辅助教学可以激发学生的学习兴趣,开阔学生眼界,加深学生对课程内容的理解,提高学生的设计能力。     

化工类专业《化工设备机械基础》教学改革初探

《化工设备机械基础》是许多化工相关专业的基础课,文章介绍了化工设备机械基础课程的教学特点,并从课堂授课、课程设计和实训课程三方面,总结出提高学生综合素质、动手能力和创新精神的教学方法。     

国内对铟的分析方法研究综述

文章对近十几年来国内关于铟元素的化学分析方法做了归纳介绍。现阶段铟的主要分析方法包括了EDTA络合滴定法、光度法、原子吸收光谱法、电感藕合等离子体法、极普法等。丰富的检测手段满足了不同含量铟的化学分析的需求,而分析方法的选择由铟在各种物料中含量的高低来确定。不论是何种物料,何种分析方法,优化实验条件成为检测过程中最为主要的工作内容,也是未来相关课题最主要的研究方向。     

面对化学工程专业的生物化工概论教学改革研究

文章根据化学工程专业学生的培养目标和生物化工概论的课程特点,系统分析和研究生物化工概论的课程体系,探讨了教学内容的选择,结合教学工作存在的问题,在教学方法和考核方式改革方面做了有益的探索,以期提高本课程的教学质量。     

谈谈化工设备机械基础的“教”与“学”

从教学实际出发,针对化工设备机械基础课时少内容多的矛盾,我们有必要在教学模式、教学内容、教学方法等方面进行改革,使“教”与“学”的过程形成有机的结合。经过不懈的努力与探索,我们在提高学生学习兴趣、知识点掌握、解决实际问题的能力以及自主创新等方面取得了较好的效果。     

胶原与明胶分子的化学基础和明胶的凝胶化

凝胶化是明胶最主要的理化性能,以明胶凝胶所测定的胶冻强度是商品明胶计价的依据。因此,从胶原和明胶分子的化学基础来了解影响明胶胶冻强度的因素,是众多明胶科学工作者所研究的重要课题之一,也是明胶生产者必备的基础知识。本文根据某些文献资料,就胶原与明胶分子的化学基础,以及它们对明胶凝胶化过程的关系作一概括性的介绍,供读者参考。     

Unraveling the Nature of Individual Recognition by Odor in Hermit Crabs

Individual recognition is a key element in the social life of many invertebrates. However, most studies conducted so far document that several species are capable of a “binary” discrimination among conspecifics, but not of a “true individual recognition.” Our objective was to learn more about the mechanisms that underlie individual recognition by odor in hermit crabs by individuating some of its properties. Using Pagurus longicarpus Say 1817 as a model species, we conducted four series of experiments in which the response of every test crab (the “receiver”) to the different odor treatments (emitted by a “sender”) was evaluated from its investigative behavior toward an empty, high-quality shell. After having excluded the possibility that crabs chemically recognize familiar/unfamiliar shells and/or shells of high/low quality, we explored whether the receivers discriminate odors from two familiar senders and whether this discrimination also occurs with unfamiliar crabs. We also asked whether crabs form an association between the odor of a familiar sender and some of its relevant attributes, i.e., rank, size, and shell quality. Finally, the shells inhabited by familiar individuals were manipulated to modify the association between odor and shell quality. Results showed that: (1) there is no odor specific of a rank; (2) individual crabs discriminate their own odor from the odor of other individuals; (3) they can chemically discriminate between larger crabs inhabiting higher-quality shells and smaller crabs inhabiting lower-quality shells, provided that these crabs are familiar to them; (4) they associate the odor of an individual crab with the quality of the shell it inhabits; and (5) this association quickly changes when social partners switch to shells of different quality. These results indicate that the nature of chemical recognition in P. longicarpus is more refined than a simple binary system. The receiver appears able to associate a type of information from the sender with memories of past experiences, therefore suggesting the hermit crab's potential for relatively high-order knowledge about conspecifics.     

Contact Sex Signals in Two Sympatric Spider Species, Tegenaria domestica and Tegenaria pagana

Bioassays in two sympatric spider species, Tegenaria domestica and T. pagana, demonstrate that the total female chemical extract, and in particular the polar fraction, are involved in the sexual behavior of males and reproductive isolation mechanisms. In T. domestica female attractiveness was correlated with changes in 18 chemical compounds. In T. pagana little difference was observed between 12 compounds in extracts of attractive and unattractive females. 12- + 10-Methyloctacosane was not detected in attractive females of either species. Reproductive isolation was linked not only to quantitative changes in 18 chemical compounds detected in both species, but also to nine compounds present in one or the other species.     

Chemical, Electrophysiological, and Behavioral Investigations on the Sex Pheromone of Lackey Moth, Malacosoma neustrium

The lackey moth Malacosoma neustrium (L.) (Lepidoptera Lasiocampidae) is a common pest of many forest and cultivated broadleaf trees. Analysis by GC-EAD of gland extracts and female effluvia showed the presence of two active peaks that were characterized as (E,Z)-5,7-dodecadienal (E5,Z7-12:Ald) and (E,Z)-5,7-dodecadienol (E5,Z7-12:OH) according to their GC retention times, mass spectra, and electroantennographic activity. (E,Z)-5,7-dodecadienyl acetate (E5,Z7-12:Ac) was also detected in the gland extracts. The average amounts of E5,Z7-12:Ald, E5,Z7-12:OH, and E5,Z7-12:Ac extracted from an abdominal tip were 113.2 +/- 22.0 ng, 29.9 +/- 6.2 ng, and 11.6 +/- 2.0 ng, respectively. In the effluvia from single females, on the average, 1.9 +/- 0.7 ng/min of aldehyde and 0.3 +/- 0.1 ng/min of alcohol were collected. In wind tunnel tests, male behavioral sequences elicited by E5,Z7-12:Ald alone or in 3:1 and 9:1 blends with the corresponding alcohol were similar to those evoked by one female equivalent of sex pheromone gland extract. Field trapping experiments showed that E5,Z7-12:Ald is essential to attract male moths. On adding E5,Z7-12:OH to E5,Z7-12:Ald in 1:3 and 1:9 ratios, male attraction slightly increased whereas in a 1:1 ratio, the attractiveness of E5,Z7-12:Ald was reduced.     

The Sister Chromatid Division of the Heteromorphic Sex Chromosomes in Silene Species and Their Transmissibility towards the Mitosis

Young sex chromosomes possess unique and ongoing dynamics that allow us to understand processes that have an impact on their evolution and divergence. The genus Silene includes species with evolutionarily young sex chromosomes, and two species of section Melandrium, namely Silene latifolia (24, XY) and Silene dioica (24, XY), are well-established models of sex chromosome evolution, Y chromosome degeneration, and sex determination. In both species, the X and Y chromosomes are strongly heteromorphic and differ in the genomic composition compared to the autosomes. It is generally accepted that for proper cell division, the longest chromosomal arm must not exceed half of the average length of the spindle axis at telophase. Yet, it is not clear what are the dynamics between males and females during mitosis and how the cell compensates for the presence of the large Y chromosome in one sex. Using hydroxyurea cell synchronization and 2D/3D microscopy, we determined the position of the sex chromosomes during the mitotic cell cycle and determined the upper limit for the expansion of sex chromosome non-recombining region. Using 3D specimen preparations, we found that the velocity of the large chromosomes is compensated by the distant positioning from the central interpolar axis, confirming previous mathematical modulations.     

Intraspecific Chemical Recognition in the Lizard Liolaemus tenuis

Experimental tests were conducted to determine whether females and males of the tree-dwelling lizard Liolaemus tenuis (Tropiduridae) show intraspecific chemical recognition during breeding and postreproductive seasons. Animals were individually maintained in plastic enclosures for one week. Thereafter, the number of tongue-flicks that a lizard performed in the enclosure of a male, a female, its own home enclosure, and a control (unused) enclosure were recorded. In both seasons, males and females made fewer tongue-flicks in their home enclosures than in any other one, indicating a recognition of a familiar place, probably a chemical self-recognition. Conspecific chemical recognition was season dependent. During the post-reproductive season, lizards tongue-flicked at similar rates in conspecific and control enclosures, while during the breeding season enclosures of females elicited more tongue-flicks by both sexes, and the overall tongue-flick rates were higher than in the postreproductive season. Results are discussed within the context of the social system of the species.     

化工生产环境中QR码的检测识别方法研究

以某化工生产企业在生产过程中使用QR码作为物料和产品的电子标签为背景,针对在化工生产中因受环境影响,致使采集到的QR码的图像大多存在一定的背景噪声,需要对图像进行二值化预处理以去除背景噪声,提出一种基于最大期望值的二值化算法并应用于QR码图像预处理中,取得了较好的效果.     

Sex Pheromone of the Pine Sawfly, Gilpinia pallida: Chemical Identification, Synthesis, and Biological Activity

We present the identification of the sex pheromone in the pine sawfly, Gilpinia pallida, including analysis of the female pheromone content, male antennal response and attraction in the field, and synthesis of the most active pheromone component. Several 3,7-dimethyl-2-alkanols were identified from female whole-body extracts, including some compounds with a 2R configuration. This is the first observation of such compounds in a pine sawfly species. Antennae of male G. pallida responded strongly in electroantennograph (EAG) recordings to the (2S,3R,7R)-isomers of the propionates of 3,7-dimethyl-2-tridecanol, 3,7-dimethyl-2-tetradecanol, and 3,7-dimethyl-2-pentadecanol, as well as to the acetates of the tri- and pentadecanols (the acetate of the tetradecanol was not tested). The propionate of (2S,3R,7R)-3,7-dimethyl-2-tetradecanol caught more males in the field than the corresponding isomer of tri- or pentadecanol. We suggest that the (2S,3R,7R)-isomer of 3,7-dimethyl-2-tetradecanol is likely the main sex pheromone precursor in G. pallida, with a subsidiary role for the (2S,3R,7R)-isomer of the tridecanol. Preparation of highly pure (2R,3R,7R)- and (2S,3R,7R)-stereoisomers of 3,7-dimethyl-2-tetradecanol, including the biological active esters, was performed via chemoenzymatic methods and is described in detail.