鱼类嗅觉系统和性信息素受体的研究进展

鱼类嗅觉系统包括外部嗅觉器官、嗅神经和嗅球三个部分.嗅觉器官也称为嗅囊,由嗅上皮和髓质组成.气味物质的化学信息主要由嗅上皮上随机分布的嗅觉感受神经元感知,通过嗅神经将嗅觉信息传递到嗅球,嗅球在空间上有不同的功能分区,嗅觉信息经过嗅球各分区整合后分别传入端脑,发挥其生理功能.性信息素在鱼类生殖过程中的作用是通过嗅觉系统来完成的,其中嗅觉感受神经元上的性信息素受体起着重要作用.鱼类性信息素受体的研究主要从两个方面入手,一是从低浓度特异的性信息素引起嗅觉器官电生理反应或行为反应入手,寻找特异的性信息素受体;二是参照哺乳动物嗅觉受体的研究结果,从嗅觉受体基因遗传保守性入手,研究鱼类性信息素受体的结构与功能.     

鱼类报警物质的研究进展

化学报警信号在鱼类的行为、生态以及与环境的互作中发挥重要作用,直接关系到鱼类的生存。根据释放条件的不同,可将鱼类化学报警信号分为焦虑物质和报警物质两种,两者均具有提醒同种个体躲避捕食风险的作用,功能上相互促进。截至目前,仅在少数几种鱼类中发现了焦虑物质,且化学本质未见报道,关于化学报警信号的研究主要集中在报警物质上。该文从报警物质的作用范畴、来源及化学特性方面,对鱼类报警物质的研究进展进行综述,以期为报警物质的进一步研究提供参考。     

农业昆虫气味受体功能研究进展

昆虫主要依靠嗅觉系统寻找食物、发现配偶、控制交配、选择产卵地、逃避天敌等,因此嗅觉系统对昆虫的繁殖和生存至关重要。气味受体(odorant receptor, OR)是嗅觉系统中的关键成分之一,可被信息化合物激活引发特定行为产生。随着测序技术的发展,大量的农业昆虫的基因组和转录组被测序,从测序数据中分析获得了它们的OR家族。现在OR功能研究经常用到外源表达系统和CRISPR/Cas9系统。外源表达系统结合记录系统可用于目标OR表达和配体筛选,CRISPR/Cas9系统可从昆虫染色体上敲除目标OR基因,进而利用电生理技术和行为学实验研究其功能。本文系统总结了鳞翅目、直翅目、半翅目、双翅目、膜翅目和鞘翅目6个目30个种的农业昆虫OR的气味分子反应谱及功能,尤其是鳞翅目农业昆虫。农业昆虫的性信息素往往是由雌虫产生的两种或两种以上成分按一定比例组成的混合物,包括在种间生殖隔离中起作用的行为拮抗剂。每个种因此具有多个性信息素的受体,共同感受这些信息素信息,调控种内和种间性行为。有些OR可调谐至主要针对植物挥发物,包括花香气味,在寄主植物选择和雌虫选择产卵地等行为中起作用。聚集信息素受体可特异地被聚集信息素激活,引起聚集行为;报警信息素受体可特异地被报警信息素激活,引起排斥行为。研究农业昆虫OR的气味分子反应谱和功能可为开发在害虫防控中应用的性诱剂、食诱剂、拒食剂、聚集信息素等奠定理论基础。最后我们对未来的主要研究方向提出了以下建议：(1)开发新的外源OR表达系统;(2)研究在雌虫中特异调谐至针对雄虫产生的性信息素的性信息素受体的功能;(3)探讨OR与气味分子之间特异性相互作用的分子机制。     

海洋哺乳动物信息素嗅觉的分子进化

研究感觉基因的进化规律是动物进化领域长期探索的重要问题.哺乳动物通常具有2套嗅觉系统:主要嗅觉系统(MOS)和犁鼻器系统(VNS).其中,VNS主要感知动物个体释放的信息素分子,而信息素在动物的生殖和社会行为中起重要调节作用.为了研究动物信息素嗅觉进化的背后推动力,对海洋哺乳动物的代表物种进行了Trpc2基因(VNS功能的分子标记)的序列测定和进化分析.以前的研究表明,Trpc2基因仅在VNS中表达,其序列完整/缺失与VNS的功能完整/退化完全一致.本研究结果显示,鲸类和海牛类的Trpc2为假基因,鳍脚类的1个分支类群(海豹类)和水獭类的Trpc2也是假基因,提示VNS功能丢失,即信息素嗅觉功能退化;而北极熊和鳍脚类的另一个分支类群(海狮类)保留了1个完整的Trpc2,并且这个基因仍受强烈的净化选择和功能限制,提示信息素嗅觉功能仍然保留.进一步分析表明,信息素嗅觉退化的海兽主要在水中交配,而信息素嗅觉保留的海兽主要在陆地上交配.本研究提出了一个新的科学假说:交配场所的选择可能推动了海洋哺乳动物信息素嗅觉的进化.     

鳞翅目蛾类雄性昆虫的信息素

鳞翅目雄性昆虫信息素释放器官结构及分布复杂多样。释放的信息素化学成分及其功能也复杂多样 ,具有种的特异性。求偶、避免种间交配、驱避同种雄性个体和驱避捕食者可能是雄性昆虫信息素的主要功能。性选择、生殖隔离和感觉系统利用是雄性昆虫信息素起源的 3种主要假说 ,而寄主转移和建立者物种形成可能与雄性昆虫信息素消失有关。     

我国昆虫信息素研究与应用的进展

用昆虫信息素防治害虫是20世纪60年代以来发展的一种治虫新技术。由于具有高效、无毒、没有污染、不伤益虫等优点,国内外对昆虫信息素的研究与应用都很重视。昆虫信息素（InsectPhernmones）是同种昆虫个体之间在求偶、觅食、栖息、产卵、自卫等过程中起通讯联络作用的化学信息物质,主要有性信息素（SexPheromones）、聚集信息素（AggregationPhero－mones）、示踪信息素（TrailPheromones）、报警信息素（AlarmPheromones）、疏散信息素（EpideicticPheromone）以及蜂王情息素（QueenPhero－mones）、那氏情息素（NosanovPheromon…     

性信息素对斜纹夜蛾雄蛾嗅觉相关基因abp,pbp和or表达的影响

【目的】信息素是个体之间传递信息的重要分子,研究性信息素对斜纹夜蛾Spodoptera litura嗅觉相关基因表达的影响对于增加性信息素作用机理的认识及其应用有重要的意义。【方法】本研究通过实时定量PCR(qRTPCR)技术探究在性信息素刺激处理条件下,斜纹夜蛾成虫嗅觉相关基因abp,pbp和or表达水平的变化;利用性信息素在田间诱捕斜纹夜蛾雄蛾,并通过自动计数器记录每小时诱虫量,从而间接显示其交配行为的节律性。【结果】斜纹夜蛾雄虫触角中嗅觉相关基因abp,pbp和or的表达具有节律特性。经性信息素化合物(Z9,Z11-14:OAc+Z9,Z12-14:OAc)刺激处理后,abp,pbp和or表达量也发生了显著的改变。通过记录田间性信息素诱捕器在一天中不同时间段内诱捕的雄蛾数量,发现诱捕到的斜纹夜蛾也具有节律特性。【结论】基因表达水平上的节律特性可能与雄虫交配活动的节律相关联,说明性信息素处理也在一定程度上改变了其节律及其对性信息素的神经反应。这一结果也首次从基因水平证明性信息素的刺激处理提高了周缘神经系统对性信息素反应的敏感性,有助于我们理解性信息素作用的分子机理,对迷向及性诱和测报应用具有指导意义。     

大型年长鱼类对海洋生态系统生物资源养护的作用

随着人口增长和渔业资源需求的上升,人类沿着食物网营养级自上向下捕捞渔业资源的趋势仍在持续,导致海洋生物多样性丧失及其生态功能与服务价值迅速下降。由捕捞活动造成的渔业诱导进化进一步导致鱼类资源小型化已受到国内外学者的广泛关注。从大型年长鱼类这一独特视角出发,综述了大型年长鱼类在种群繁衍过程中的作用,其具备巨大的繁殖能量输出、丰富的亲本繁殖经验以及强大的年龄组繁殖力贡献,更有利于种群的延续;大型年长鱼类对于初次性成熟亲鱼生殖洄游具有一定的引领作用,并在季节性集群繁殖过程中占据主导地位,可通过抑制小个体同类繁殖维护种群结构的稳定;大型年长鱼类在生态系统中更是占据了较高营养级和广阔的生态位宽度,面对生态环境的改变,具有更强的适应调控能力;大型年长鱼类在种群基因交流过程中亦起到十分关键的作用。保护大型年长鱼类更有利于鱼类种群的快速恢复,这为生物资源养护和渔业管理政策制定方面提供了一定的参考。     

蛾类昆虫性信息素受体及其作用机理

蛾类昆虫性信息素受体首先从烟芽夜蛾Heliothis virescens和家蚕Bombyx mori中鉴定出来, 到目前为止已经克隆得到了19种蛾类昆虫的几十种性信息素受体基因, 并且这些基因在系统发育树中聚成一个亚群。性信息素受体从蛾类蛹期开始表达, 主要表达在雄性触角的毛形感器中, 少部分受体在雌性触角、 雄性触角其他感器以及身体其他部位中也有表达。大部分蛾类性信息素受体的配体并不是单一的, 而是能够对多种性信息素组分有反应, 部分性信息素受体还能够识别性信息素以外的其他物质, 还有一部分性信息素受体的识别配体目前尚不清楚。另外发现在雌性蛾类触角中也存在一些嗅觉受体能够识别雄性分泌的性信息素。在蛾类性信息素受体与性信息素识别的过程中, 性信息素结合蛋白不仅能够特异性地运送配体到嗅觉神经元树状突上, 还能够提高性信息素与性信息素受体之间的结合效率。另外, OrCo类受体与性信息素受体共表达在嗅觉神经元中, 在蛾类性信息素受体与配体的识别过程中扮演了重要角色。但是蛾类信息素对神经元刺激的终止并非由性信息素受体控制, 而是由细胞中的气味降解酶等其他因子调控。蛾类性信息素受体研究中还有很多疑问需要解答, 其过程可能比我们想象的更为复杂。     

八角尺蠖对八角叶及性信息素腺体浸提液的触角电位反应

触角电位(electroantennogram,EAG)技术是一个在昆虫性信息素和其它挥发性信息化学生物活性测定中的重要方法。本研究利用EAG技术,测定了八角尺蠖对丙酮、正己烷、乙醇和蒸馏水等4种不同溶剂所浸提的八角叶片及八角尺蠖性信息素腺体浸提液的电生理反应。结果表明,正己烷是八角尺蠖性信息素提取的最好溶剂,雄蛾对性信息素腺体浸提液的EAG反应比雌虫强烈,这在一定程度上反映了雄蛾可能更依赖于对雌蛾释放的性信息素的探测,而不是对寄主气味的探测;雄蛾对八角叶片的正己烷浸提液具有最强的EAG反应,而雌蛾则对八角叶片的丙酮浸提液的EAG反应最强,由此反映了雌雄个体在寻找寄主、繁殖后代等行为中的性别差异;雄蛾羽化后3h对八角叶片气味就有较强的EAG反应,在24h内EAG反应值随着羽化后时间的延长而增大,这反映了随着羽化后时间的延长,触角的机能随之趋于完善,因此对于外界的刺激更为敏感。本研究为利用八角尺蠖性信息素活性成分开展害虫的监测和无公害防治奠定基础。     

Modulatory role of testosterone in alarm pheromone release by male rats

An alarm pheromone released from stressed conspecifics evokes behavioral and autonomic responses in rats. We have previously reported that male Wistar rats show behavioral changes including increased sniffing, walking and rearing, and decreased resting as well as exaggerated response of body temperature to a novel environment [known as stress-induced hyperthermia (SIH)] when they are exposed to an alarm pheromone released from other male rats receiving foot shocks. The purpose of the present study was to examine the role of testosterone in the production and release of the alarm pheromone using these behavioral and autonomic responses in recipient rats. Three groups of alarm pheromone donors were presented, namely, intact males, castrated males, and testosterone-implanted castrated males. The effects of the alarm pheromone on the autonomic responses did not differ among the three groups, regardless of the donor's steroidal milieu, whereas behavioral responses were altered by castrating the donor males and the effects were restored by testosterone implantation. These results suggest that the alarm pheromone released from stressed male rats can be classified into at least two categories according to the androgen dependency of their production and/or release.     

Chemical Predator Inspection in a Characin Fish (Hemigrammus erythrozonus, Characidae, Ostariophysi): The Effects of Mixed Predator Diets

Many prey organisms will approach (inspect) potential predators, primarily to assess local risk of predation. It has been demonstrated that Ostariphysan prey fishes can detect conspecific alarm pheromones in the diet of potential predators and use this chemical information to reduce their risk of predation while still gaining significant benefits associated with predator inspection. We conducted the current study to examine the possible effects of mixed diets on the use of these chemical predator diet cues during inspection visits. Shoals of four glowlight tetras ( Hemigrammus erythrozonus ) were exposed to Jack Dempsey cichlids ( Cichlasoma octofaciatum ) which had been fed diets consisting of: 100% tetras (with alarm pheromone); 75% tetra, 25% swordtail ( Xiphophorus helleri , which lack a recognizable alarm pheromone); 25% tetra, 75% swordtail; or 100% swordtails. Tetras significantly increased their anti-predator behaviour in response to predators fed 100% tetra or the two mixed predator diets, but not when exposed to predators fed a 100% swordtail diet. Likewise, we observed significant differences in inspection behaviour. Tetras took longer to initiate an inspection, inspected in smaller groups and directed a greater proportion of inspection visits towards the tail region of the predator when it had been fed 100% tetra or either of the two mixed prey diets. We found no significant differences in either anti-predator or inspection behaviour among the three diet treatments containing tetras. These data strongly suggest that glowlight tetras are capable of detecting relatively small amounts of conspecific alarm pheromone in the diet of potential predators and that they modify their behaviour based on the presence or absence of these cues.     

Context‐dependent alarm signalling in an insect

Animals often respond to danger by raising alarm to inform others. Alarm signals come in many different forms, such as visual or mechanical display, sound or odour. Some animals produce vocal alarm signals that vary with the level of danger. For chemical alarm signals, virtually nothing is known about such context‐dependent signalling due to a general notion that alarm pheromones have fixed compositions. Here, we show that larvae of the Western Flower Thrips (Frankliniella occidentalis) produce an alarm pheromone whose composition varies with the level of danger they face: the presence of a relatively harmless predator or a very dangerous predator, that is either actually attacking or not. The frequency of alarm pheromone excretion increases with the level of danger. Moreover, the composition of excreted alarm pheromone varies in the relationship between total and relative amount of the putative two components, decyl acetate (DAc) and dodecyl acetate (DDAc). When pheromone is excreted with a predator present but not attacking, the percentage DDAc increases with the total amount of pheromone. When a predator does attack, however, the relationship between percentage DDAc and total amount of pheromone is reversed. Taken together, the alarm signal of thrips larvae appears to be context dependent, which to our knowledge is the first report of context‐dependent composition of an alarm pheromone.     

Alarm pheromone mediates production of winged dispersal morphs in aphids

The aphid alarm pheromone ( E )- β -farnesene (EBF) is the major example of defence communication in the insect world. Released when aphids are attacked by predators such as ladybirds or lacewing larvae, aphid alarm pheromone causes behavioural reactions such as walking or dropping off the host plant. In this paper, we show that the exposure to alarm pheromone also induces aphids to give birth to winged dispersal morphs that leave their host plants. We first demonstrate that the alarm pheromone is the only volatile compound emitted from aphid colonies under predator attack and that emission is proportional to predator activity. We then show that artificial alarm pheromone induces groups of aphids but not single individuals to produce a higher proportion of winged morphs among their offspring. Furthermore, aphids react more strongly to the frequency of pheromone release than the amount of pheromone delivered. We suggest that EBF leads to a 'pseudo crowding' effect whereby alarm pheromone perception causes increased walking behaviour in aphids resulting in an increase in the number of physical contacts between individuals, similar to what happens when aphids are crowded. As many plants also produce EBF, our finding suggests that aphids could be manipulated by plants into leaving their hosts, but they also show that the context-dependence of EBF-induced wing formation may hinder such an exploitation of intraspecific signalling by plants.     

Removal of the vomeronasal organ blocks the stress-induced hyperthermia response to alarm pheromone in male rats

Previously, we reported that male Wistar rats release alarm pheromone from their perianal region, which aggravates stress-induced hyperthermia (SIH) in pheromone-recipient rats. The subsequent discovery that this pheromone could be trapped in water enabled us to expose recipients to the pheromone in their home cages. Despite its apparent influence on autonomic and behavioral functions, we still had no clear evidence as to whether the alarm pheromone was perceived by the main olfactory system (MOS) or by the vomeronasal system. In this study, we investigated this question by exposing 3 types of recipients to alarm pheromone in their home cages: intact males (Intact), vomeronasal organ-excised males (VNX), and sham-operated males (Sham). The Intact and Sham recipients showed aggravated SIH in response to alarm pheromone, whereas the VNX recipients did not. In addition, the results of the habituation/dishabituation test and soybean agglutinin binding to the accessory olfactory bulb verified the complete ablation of the vomeronasal organ (VNO) with a functional MOS in the pheromone recipients. These results strongly suggest that male rats perceive alarm pheromone with the VNO.     

Alarm pheromone that aggravates stress-induced hyperthermia is soluble in water

We previously reported that stressed male Wistar rats released alarm pheromone from the perianal region, which aggravated stress-induced hyperthermia and increased Fos expression in the mitral/tufted cell layer of the accessory olfactory bulb in recipient rats. In this study, we attempted to obtain this pheromone in water using these responses as bioassay parameters. Water droplets were collected from the ceiling of a box in which no animal was placed, or from a box in which an anesthetized donor rat was given electrical stimulation to either the neck or perianal regions in order to induce neck odor or alarm pheromone release, respectively. Then we placed one of the three kinds of water-containing filter papers on the wall of a recipient's home cage and observed heart rate, body temperature and behavioral responses, as well as Fos expression in the main and accessory olfactory bulbs of the recipient. The water collected from the box containing the alarm pheromone was found to generate a reproduction of all of the responses seen in the animal that had been directly exposed to alarm pheromone in our previous studies. These results suggest that the alarm pheromone is soluble in water.     

Pretreatment with CP-154526 blocks the modifying effects of alarm pheromone on components of sexual behavior in male, but not in female, rats

We previously demonstrated that an alarm pheromone released from male donor Wistar rats evoked several physiological and behavioral responses in recipient rats. However, the pheromone effects on social behavior were not analyzed. In the present study, we examined whether the alarm pheromone affects sexual behavior in male or female rats. When a pair of male and female subjects was exposed to the alarm pheromone during sexual behavior, the ejaculation latency was elongated, the number of mounts was increased, and the hit rate (number of intromissions/number of mounts and intromissions) was decreased in the male subject. In contrast, female sexual behavior was not affected by the alarm pheromone. When we exposed only the male or female subject of the pair to the pheromone just before sexual behavior, the results were similar: the pheromone effects were evident in male, but not in female, subjects. In addition, when we pretreated with corticotropin-releasing factor (CRF) antagonist (CP-154526) before exposing the male subject to the alarm pheromone, the pheromone effects were attenuated in a dose-dependent manner. These results indicate that the alarm pheromone modifies male, but not female, components of sexual behavior and that CRF participates in the effects.     

Cues of Predation Risk Induce Instar‐ and Genotype‐Specific Changes in Pea Aphid Colony Spatial Structure

Deploying collective antipredator behaviors during periods of increased predation risk is a major determinant of individual fitness for most animal groups. Pea aphids, Acyrthosiphon pisum, which live in aggregations of genetically identical individuals produced via asexual reproduction warn nearby conspecifics of pending attack by secreting a volatile alarm pheromone. This alarm pheromone allows clone‐mates to evade predation by walking away or dropping off the host plant. Here, we test how a single alarm pheromone emission influences colony structure and defensive behavior in this species. Relative to control colonies, groups exposed to alarm pheromone exhibited pronounced escape behavior where many individuals relocated to adjacent leaves on the host plant. Alarm pheromone reception, however, also had subtle instar‐specific effects: The proportion of 1st instars feeding nearest the leaf petiole decreased as these individuals moved to adjacent leaves, while the proportion of 2nd–3rd instars feeding nearest the leaf petiole remained constant. Fourth instars also dispersed to neighboring leaves after pheromone exposure. Lastly, alarm pheromone reception caused maternal aphids to alter their preferred feeding sites in a genotype‐specific manner: Maternal aphids of the green genotype fed further from the petiole, while maternal aphids of the pink genotype fed closer to the petiole. Together, our results suggest that aphid colony responses to alarm pheromone constitute a diversity of nuanced instar‐ and genotype‐specific effects. These behavioral responses can dramatically change the spatial organization of colonies and their collective defensive behavior.     

An ambiguous function of an alarm pheromone in the collective displays of the Australian meat ant,Iridomyrmex purpureus

Alarm pheromones, which have been documented in many species of ants, are thought to elicit responses related to aggressive or defensive behaviour. The volatile odour 6-methyl-5-hepten-2-one is described as an alarm pheromone in several species of ants, including the Australian meat ant, Iridomyrmex purpureus. The alarm pheromone is released by displaying workers that aggregate in the characteristic collective display grounds, located mid-way between colonies or near contested food trees. Workers are typically more aggressive at the latter location, and the alarm pheromone may regulate the collective level of aggression. We investigated this possibility by exposing displaying workers to synthesised alarm pheromone 6-methyl-5-hepten-2-one in a field experiment, and measuring their aggressive behaviour. We found no evidence that exposure to synthesised alarm pheromone caused changes in the aggressive level of workers. Subsequent field experiments revealed that the pheromone functions as an attractant, thereby increasing the density of displaying workers. More densely populated workers also display more aggressively, indicating that the interaction rate of displaying workers may determine the level of aggression in collective displays. This underlying mechanism can explain why displaying ants are more aggressive at the more densely populated food-tree locations than those displaying at locations midway between two neighbouring colony nest sites.     

Antipredator responses to alarm pheromone in groups of young and/or old thrips larvae

Many prey species suffer from different predators in the course of their ontogeny. Hence, the alarm signal a small prey individual sends can have a different meaning than the signal a large prey individual sends, both for small and for large receivers. Larvae of Western Flower Thrips face predators that attack only small larvae, or predators that attack small larvae and large larvae. Furthermore, thrips larvae release a two‐component alarm pheromone, which varies in composition with larval age. Here, we study whether their response to alarm pheromone varies with composition of the pheromone. First, we confirmed that large and small larvae respond when nearby larvae of both sizes were prodded with a brush to induce alarm pheromone excretion. Subsequently, we tested whether thrips larvae of a given size respond differentially to alarm pheromone excreted by a small or large companion larva. We analyzed two types of behavior used in direct defense against a predator and one type of escape response. Only small (not large) larvae attempted to escape more frequently in response to excretions from a large larva. This difference in response could have been due to the alarm pheromone or to the companion larva in the vicinity. We subsequently tested for, but did not find, an effect of size of the companion larva on the behavior of the test larva when exposed to synthetic pheromone mimicking that of a large larva. Finally, we tested how pheromone composition affects antipredator behavior by exposing thrips larvae to synthetic pheromones differing in amount and ratio of the two components. Only for small larvae, we found significant changes in escape behavior with pheromone amount, and a trend with the ratio. Overall, we conclude that small thrips larvae respond differentially to alarm pheromones excreted by small and large larvae and that this differential response is due to differences in pheromone quantity and possibly also quality. Our results suggest that responses to alarm signals can vary with the chemical composition of those alarm signals.