Ontogeny of Ultrasonic and Locomotor Responses to Nest Odors in Rodents

SYNOPSIS. Rodents discriminate and prefer familiar odors earlyin life. Almost from birth young rats suckle in response tomaternal odor, but suckle less when nipples are cleaned withorganic solvents. In two-choice tests, young prefer familiarnest odors, whether naturally occurring or artificially presented,and can even be made to tolerate odors normally aversive orto avoid odors normally pleasant. Variations in maternal dietcan alter odor preferences of theyoung. Nest odors can affect vocalization of young rodents. In contrastto the consistent effects of cold temperature and handling inthe many rodents studied, nest odors may affect vocalizationdifferently in different species. For example, familiar odorsreduce calling in rats, but increase calling in pine voles.Nest odor also alters spontaneous activity in young rats, whichlocomoteless when maternal odor is present. In this paper I report that home nest odors enhanced locomotionin rodents of three species (pine voles, Microtus pinetorum;white-footed mice, Peromyscus leucopus; and wild house mice,Mus musculus), but that the age at which this pattern occurredand the relationships of nest odors to vocalizations differedamong the species.     

Divergence of odorant signals within and between the two European subspecies of the house mouse

The olfactory acuity of mice allows them to discriminate odorsof conspecifics differing by a few genes. This acuity is usedin habituation procedures where investigation of novel odorsby the mouse can be translated into relative difference or similaritybetween the stimuli. This study adapts these behavioral proceduresto address suprapopulation divergence among urinary odors inthe house mouse. Specifically, we investigate geographical patternsof odor divergence within and between 2 subspecies of the housemouse, Mus musculus musculus and Mus musculus domesticus, whichdiverged in allopatry and met secondarily in Europe where theyhybridize. Based on M. m. musculus perception, our study suggeststhat odors of the 2 subspecies differ in both allopatric andcontact zone populations and that divergence is more markedin the latter. Our earlier studies documented mate preferenceand signal divergence between the 2 subspecies. Hence, we considerthe role of the urinary odors as mating signals. We discusshow signal divergence between the 2 subspecies may relate toreproductive character displacement. This study validates theuse of habituation procedures to reconstruct geographical patternsof odorant signal divergence, providing a strong methodologicalplatform to address reproductive character displacement affectingcryptic mating signals in mammals.     

Facial EMG responses to odors in solitude and with an audience

Two experiments were undertaken to examine whether facial responsesto odors correlate with the hedonic odor evaluation. Experiment1 examined whether subjects (n = 20) spontaneously generatedfacial movements associated with odor evaluation when they aretested in private. To measure facial responses, EMG was recordedover six muscle regions (M. corrugator supercilii, M. procerus,M. nasalis, M. levator, M. orbicularis oculi and M. zygomaticusmajor) using surface electrodes. In experiment 2 the experimentalgroup (n = 10) smelled the odors while they were visually inspectedby the experimenter sitting in front of the test subjects. Thecontrol group (n = 10) performed the same experimental conditionas those subjects participating in experiment 1. Facial EMGover four mimetic muscle regions (M. nasalis, M. levator, M.zygomaticus major, M. orbicularis oculi) was measured whilesubjects smelled different odors. The main findings of thisstudy may be summarized as follows: (i) there was no correlationbetween valence rating and facial EMG responses; (ii) pleasantodors did Dot evoke smiles when subjects smelled the odors inprivate; (iii) in solitude, highly concentrated malodors evokedfacial EMG reactions of those mimetic muscles which are mainlyinvolved in generating a facial display of disgust; (iv) thosesubjects confronted with an audience showed stronger facialreactions over the periocular and cheek region (indicative ofa smile) during the smelling of pleasant odors than those wbosmelled these odors in private; (v) those subjects confrontedwith an audience showed stronger facial reactions over the M.nasalis region (indicative of a display of disgust) during thesmelling of malodors than those who smelled the malodors inprivate. These results were taken as evidence for a more socialcommunicative function of facial displays and strongly mitigatesthe reflexive-hedonic interpretation of facial displays to odorsas supposed by Steiner.     

大豆蚜嗅觉在选择寄主植物中的作用

大豆蚜 Aphis hlycines 有翅和无翅孤雌生殖蚜为其寄主植物大豆叶和鼠李叶气味所引诱,而非寄主植物棉花叶和黄瓜叶气味处于中性,丝瓜叶和南瓜叶气味具有明显的排斥作用。非寄主植物气味可以遮蔽寄主植物气味的引诱作用。大豆蚜触角感受器对植物气味具有嗅觉生理反应,对一些化合物的最小感觉阈值达10-5至10-6体积比浓度,表明大豆蚜触角上存在识别植物气味的嗅觉受体细胞。由此证明,嗅觉在大豆蚜选择寄主植物过程中起重要作用。     

Copepod reaction to odor stimuli influenced by cestode infection

The cestode Schistocephalus solidus uses copepods as first andsticklebacks as second intermediate hosts. For transmission,an infected copepod has to be preyed upon by a stickleback.We used copepods of the species Macrocy albidus to test whetherinfected and uninfected copepods differ in their reaction totwo kind of simultaneously presented odors: odors of sticklebacksand odors of sticklebacks and conspecificz. By giving this choice,we attempted to force the copepods to make a trade-off betweenthe benefit of risk dilution and possible predator confusionand the costs of food competition and other disadvantages inducedby conspecifics. Within 1–8 h after last feeding, uninfectedcopepods clearly preferred the odors of conspeciflcs under thechemically simulated threat of predation. This was in contrastto the infected copepods, who tended to avoid the odor of conspecifics.When the time between experiment and last feeding varied, infectedcopepods showed an increas preference for fish water only (oravoided conspecthcs) with increasing hunger level This suggeststhat S. solidus benefits from hunger-induced behavioral changesof its copepod host by influencing its microhabitat selection.The same effect could be found in both sexes; however, it wassignificantly more pronounced in male than in female copepods.We propose several hypotheses that could explain the differencebetween the sexes in their infection-dependent microhabitatselection.     

Chemical communication in an archaic anuran amphibian

Bioacoustic signals appear to be so essential to the socialcommunication of anuran amphibians that other sensory modalitieshave been largely ignored. We studied the abilities of Leiopelmahamiltoni, a species evolutionarily basal to most living anurans,to communicate by means of chemosignals. We collected frogsin the field, held them in captivity for 72 h, and then testedtheir preferences for substrates that they had marked themselvesto those marked by conspecifics. Individuals preferred papertowels that they had marked themselves to those marked by frogscollected from other home ranges. Preferences were greater,on average, when the conspecific had been collected fartheraway. Frogs did not discriminate between their own odor andthose of other individuals with which they had shared a homerange. Individuals preferred their own odor to a blank unmarkedtowel but also avoided odors of unfamiliar conspecifics whenpaired with a blank. The discovery of chemical communicationin an archaic anuran offers a window into how frogs may havecommunicated before mechanisms of bioacoustic signaling evolved.We suggest, however, that chemical signaling may be widespreadin anuran amphibians.     

Non-warning odors trigger innate color aversions--as long as they are novel

Warning signals made by unpalatable insects to potential predatorscommonly target more than one sense: such signals are "multimodal." Pyrazines are odors produced by warningly colored insects whenattacked, and have been shown to interact with food coloration,biasing avian predators against novel and typically aposematicfood. However, at present it is not known whether this is anadaptation by prey to exploit a general feature of avian psychology,or an evolutionary response by birds to enhance their avoidanceof unpalatable prey. Here we investigate the effect of otherodors on the innate responses of naive domestic chicks (Gallusgallus domesticus) to food that is of novel color, or of acolor that is associated with warning coloration, yellow. Inthe first experiment, we demonstrate that natural and artificialodors that have no association with aposematism in the wildcan produce biases against both novel colored foods and yellowcolored foods. In a second experiment, we also show that odor novelty is vital for eliciting such effects. These results supportthe idea that warning odors have evolved in response to preexistingpsychological biases against novel odors in predators, ratherthan predators evolving specific responses against odors associatedwith unpalatable prey.     

Olfactory stimulus control in the rat

Discrimination training in which introduction of S– waspreceded by 250 S + trials resulted in errorless learning inrats trained to discriminate between two odors or tones versuslights, but not in those trained to discriminate between twolights or two tones. In a second study rats were trained todiscriminate odor, lights, or lights versus tones and then givena series of 10 successive discrimination reversals. Only ratstrained with odors showed positive transfer on the first reversaland acquisition of a learning-set. These results, together withthose of others, indicate that rats show exceptionally rapidacquisition of operant discriminations when trained with odorsand that this performance superiority is probably because odorsprovide more salient cues than do tones or lights.     

Odor suppression of voltage-gated currents contributes to the odor-induced response in olfactory neurons

Olfactorychemotransduction involves a signaling cascade. In addition totriggering transduction, odors suppress ion conductances. Bystimulating with brief odorant pulses, we observed a current associatedwith odor-induced suppression of voltage-gated conductances and studiedits time dependence. We characterized this suppression current inisolated Caudiverbera caudiverberaolfactory neurons. All four voltage-gated currents are suppressed byodor pulses in almost every neuron, and suppression is caused by odorsinducing excitation and by those inducing inhibition, indicating anonselective phenomenon, in contrast to transduction. Suppression has a10-fold shorter latency than transduction. Suppression was morepronounced when odors were applied to the soma than to the cilia,opposite to transduction. Suppression was also present in rat olfactory neurons. Furthermore, we could induce it inDrosophila photoreceptor cells,demonstrating its independence from the chemotransduction cascade. Weshow that odor concentrations causing suppression are similar to thosetriggering chemotransduction and that both suppression and transductioncontribute to the odor response in isolated olfactory neurons.Furthermore, suppression affects spiking, implying a possiblephysiological role in olfaction.

     

Gonadal control of male scent in the tarmarin Saguinus fuscicollis (Callitrichidae, Primates)

Spontaneous responses to the scent marks of male Saguinus fuscicolliswere tested in experiments where the subjects received a choicebetween scent of intact males and castrated males. Male tamarinsdiscriminated between the odors of intact and castrated males,both on the basis of fresh individual scent marks and on thebasis of marks from several donors pooled in methanol. Theirdiscriminatory response to pooled odors was more pronouncedthan that to individual odors. Females discriminated betweenintact and castrated male scents only on the basis of pooledsamples. This result shows that castration causes changes inthe odor of males. The difference in the response of the tamarinsto individual scent marks as compared to pooled samples is discussedin terms of quantitative changes caused by extraction and ofindividual recognition.     

Odor similarity does not influence the time needed for odor processing

The brain's link between perception and action involves several steps, which include stimulus transduction, neuronal coding of the stimulus, comparison to a memory template and choice of an appropriate behavioral response. All of these need time, and many studies report that the time needed to compare two stimuli correlates inversely with the perceived distance between them. We developed a behavioral assay in which we tested the time that a honeybee needs to discriminate between odors consisting of mixtures of two components, and included both very similar and very different stimuli spanning four log-concentration ranges. Bees learned to discriminate all odors, including very similar odors and the same odor at different concentrations. Even though discriminating two very similar odors appears to be a more difficult task than discriminating two very distinct substances, we found that the time needed to make a choice for or against an odor was independent of odor similarity. Our data suggest that, irrespective of the nature of the olfactory code, the bee olfactory system evaluates odor quality after a constant interval. This may ensure that odors are only assessed after the olfactory network has optimized its representation.     

Specialized receptor neurons for pheromones and host plant odors in the boll weevil, Anthonomus grandis Boh. (Coleoptera: Curculionidae)

Antennal olfactory receptor neurons in the boll weevil, Anthonomusgrandis, were investigated through single neuron recordings.Receptor neurons for both pheromone components and host plantodors were associated with type I sensilla within the sensoryband regions. Nine types of receptor neurons were identified,based on their responsiveness to the four aggregation pheromonecomponents and selected host plant odors. Three receptor neurontypes responded to either compound I, II or IV of the aggregationpheromone. Dose—response curves were similar for eachof these receptor neuron types, which differed only in theirkey compound. In each instance, I neurons responded primarilyto (+)-I, the optical isomer produced by the boll weevil whichwas found to be active in field tests. Receptor neurons forII also responded to a lesser degree to III, its aldehydic analog,at the same stimulus load. Six additional receptor neuron typesresponded to selected host plant odors: ß-caryophyllene,trans-2-hexen-l-o1 and other six carbon alcohols and aldehydes,trans-ß-ocimene, benzaldehyde, linalool, and B-bisabolol.These neurons were as responsive as, or in some cases more responsiveat the same stimulus load as receptor neurons for pheromonecomponents. Receptor neurons responsive to six-carbon alcoholsand aldehydes were generally most responsive to trans-2-hexen-l-ol.Receptor neurons for other plant odors responded principallyto only one compound among the odorants tested. However, responsesof these neurons were not uniform, suggesting possible specializationfor other unidentified key odorants. Comparisons were also madebetween single neuron and electroantennogram responses. Theresults indicate that the boll weevil, a narrowly oligaphagousinsect, detects its host plant at some distance, and utilizesinformation about a wide range of chemical structures in itsolfactory-mediated behavior.     

On the role of chirality in structure-odor relationships

The influence of chirality on odors was studied on 16 enantiomericpairs according to the dispersion/hydrogen bonding theory ofreceptor-odorant interaction. Comparisons of molecular structures were made by superimpositionof optimized conformations, using the Alchemy II package. Thequality of fit was assessed using the RMS parameter includedin Alchemy II and a new index for hydrogen bonding: the anglebetween H-bonds in the two molecules. In the case of camphoraceous odorants where an interaction modelwas already known superimposition according to the model ledto correct predictions of the high similarity of odors observedin enantiomeric pairs. For several urinous odorants comparisons were made using d-androstenoneas a reference compound for the urinous odor. Correct predictionswere obtained for l-androstenone, both enantiomers of androsta-4,16-dienone, and (+)-2-methyl-4-(5,5,6-exo-trimethy1-2-exonorbornyl)-cyclobexane.The (–) enantiomer of the latter compound was correctlypredicted only if it was assumed that its weak intensity isdue to a partial interaction with the hydrophobic zone of thereceptor. For ambergris odorants which have a complex odor (–)-Ambroxwas selected as the reference compound. The odors of (+)-Ambroxand enantiomers of four other compounds (ambergris or woody)were correctly predicted by superimposition. For nootkatone and three derivatives which have a grapefruitnote for one enantiomer and a woody note for the other no modelsor reference compounds were available. The superimpositionswere made between grapefruit enantiomers, on the one hand, andwoody enantiomers on the other hand. Woody and grapefruit characterswere correctly predicted in all cases. The limits of this approach based on molecular modelling arediscussed.     

Communication by scent in some Callitrichidae (Primates) - An interdisciplinary approach

In the South American primate, Saguinus fuscicollis, complexscent marks consisting mainly of the secretions of specializedcircumgenital skin glands and some urine communicate the identityof the species, subspecies and individual, its gender, hormonalcondition and social status. The volatile constituents of thesemarks are squalene and a series of butyric acids, comprising96% (by weight) of the mark, and also a large number of as yetunidentified highly volatile compounds. Monitoring of the relativeconcentrations of squalene and the butyrate esters in the scentmarks of male Saguinus f. fuscicollis and Saguinus f. illigeridemonstrates that the two subspecies show consistent differencesin their concentration profiles. The profiles of individualpurebred males closely resemble those of the appropriate subspecieswhile those of hybrids do not. Moreover, the concentration profilesof individual purebred males and hybrids are remarkably constantover long periods of time. Behavioral studies suggest that specificratios of these compounds may be involved in encoding subspeciesspecificity. However, synergists from the highly volatile compoundsappear to be necessary for complete encoding of the message.     

Evolution and Function of Drumming as Communication in Mammals

An amazing variety of mammals produce seismic vibrations bydrumming a part of their body on a substrate. The drumming cancommunicate multiple messages to conspecifics about territorialownership, competitive superiority, submission, readiness tomate, or presence of predators. Drumming also functions in interspecificcommunication when prey animals drum to communicate to predatorsthat they are too alert for a successful ambush. The diversityof mammals that drum in varied contexts suggest independentevolution in different lineages. Footdrumming, as with othersignals, probably originated by ritualization of older formsof behavior not associated with communication such as runningand digging. Footdrumming patterns are species specific andrange from single thumps to individual footdrum signatures.Although mammals communicate above ground with airborne drummingsignals, they can also transmit sound seismically into the burrowwhere the signals become airborne and are received with earsespecially adapted to hear low-frequency sound. Footdrumminghas been studied the most extensively in kangaroo rats, Dipodomys.A comparison of species of different body mass shows that smallersized, non-territorial species have no ritualized footdrumming;medium-sized species drum a simple pattern in limited contexts;while larger-sized species communicate territorial ownershipwith complex patterns. Future studies should examine the mechanicsand energy requirements of drumming to test hypotheses aboutbody size limitations on the evolution of footdrumming. Ourunderstanding of drumming as communication is limited untilinvestigators conduct field tests of responses to drumming signalsin the contexts in which the signals are generated.     

Scent marking by voles in response to predation risk: a field-laboratory validation

Predators use scent to locate their prey, and prey animals oftenalter their behavior in response to predation risk. I testedthe hypothesis that voles would decrease their frequency ofscent marking in response to predation risk. I conducted trialsin which prairie voles, Microtus ochrogaster, and woodland voles,M. pinetorum, were allowed to scent mark ceramic tiles placedin their runways in the field. The tiles were subjected to oneof three treatments: scented with odor from mink, Mustela vison(a rodent predator); rabbit, Oryctolagus cuniculus (a nonpredatormammal control); and no odor (control). No significant differenceswere found in the frequency of scent marking in response tothe three treatments for either species. To validate that volesdid not decrease their scent marking in response to predationrisk, I brought male prairie voles from the field site intothe laboratory and allowed them to scent mark white paper substratetreated with mink odor, rabbit odor, or no odor. No significantdifferences were found in the frequency of scent marks in responseto the three treatments. These results differ from what waspredicted based on laboratory studies with other species ofrodents that show avoidance, reproductive suppression, decreasedactivity, and reduced scent marking in response to odors ofpredators. Voles appear to scent mark different substrates andunder a wide variety of social and environmental situations,and this is not influenced by the presence of odor from a predator.     

棉铃虫气味受体的克隆与组织特异性表达

气味受体在昆虫识别外界气味过程中起重要作用,对其的研究可以帮助我们了解昆虫对气味识别的分子机制。本文通过RT-PCR技术,在棉铃虫Helicoverpa armigera (Hübner)中克隆得到11条气味受体序列（GenBank登录号：EU599565～EU599568,EU818702～EU818706,FJ393455）。序列分析结果表明,HarmOR2为非典型气味受体,其他为典型气味受体。进化树显示,HarmOR10与黑腹果蝇Drosophila melanogaster DOR46a进化关系较近,而HarmOR4与果蝇味觉受体聚类在一起。棉铃虫其余气味受体与烟芽夜蛾Heliothis virescens气味受体单独或几个一起处于与黑腹果蝇气味受体进化关系较远的聚类中,而且彼此聚类关系较远。使用半定量RT-PCR对这些气味受体的表达谱进行研究,结果表明: HarmOR2在棉铃虫触角和喙中表达,表达量在雌雄间相当。其他受体则在成虫触角中特异表达,其中HarmOR3,HarmOR13和HarmOR14仅在雄性触角内表达; 雌性触角内HarmOR12和HarmOR20的表达量要高于雄性触角;其余气味受体雌雄触角间表达量则相当。     

Food resources, chemical signaling, and nest mate recognition in the ant Formica aquilonia

Animals such as social insects that live in colonies can recognizeintruders from other colonies of the same or different speciesusing colony-specific odors. Such colony odors usually haveboth a genetic and an environmental origin. When within-colonyrelatedness is high (i.e., one or very few reproductive queens),colonies comprise genetically distinct entities, and recognitionbased on genetic cues is reliable. However, when nests containmultiple queens and colonies comprise multiple nests (polydomy),the use of purely genetically determined recognition labelsmay become impractical. This is due to high within-colony geneticheterogeneity and low between-colony genetic heterogeneity.This may favor the use of environmentally determined recognitionlabels. However, because nests within polydomous colonies maydiffer in their microenvironment, the use of environmental labelsmay also be impractical unless they are actively mixed amongthe nests. Using a laboratory experiment, we found that bothisolation per se and diet composition influenced the cuticularchemical profiles in workers of Formica aquilonia. In addition,the level of aggression increased when both the proportionsof dietary ingredients and the availability of food were altered.This suggests that increased aggression was mediated by changesin the chemical profile and that environmental cues can mediaterecognition between colonies. These results also suggest thatthe underlying recognition cues are mutable in response to extrinsicfactors such as the amount and the composition of food.     

中红侧沟茧蜂化学感受蛋白MmedCSP1的结合特征

化学感受蛋白是一类存在于昆虫化学感受器中的可溶性蛋白, 被认为与昆虫识别外界化学信息有关。本研究使用pGEX-4T-1表达载体在BL21 (DE3)异源表达系统中表达中红侧沟茧蜂Microplitis mediator化学感受蛋白MmedCSP1, 并通过亲和层析法纯化得到去表达标签的MmedCSP1;使用bis-ANS作为荧光配基, 在荧光分光光度计上研究它与50种气味标样的结合特征, 从而得到此类化学感受蛋白在中红侧沟茧蜂嗅觉识别中识别气味的种类。结果表明: MmedCSP1只能与水杨酸甲酯、戊烷、罗勒烯、β-紫罗兰酮、3, 4-二甲基苯甲醛、2-己酮和叶醇结合。但只有脂类化合物β-紫罗兰酮能在浓度为1 mmol/L下将bis-ANS从MmedCSP1中替换50%, β-紫罗兰酮与MmedCSP1的结合常数为16.89 μmol/L。这些结果提示MmedCSP1参与中红侧沟茧蜂对水杨酸甲酯、戊烷、罗勒烯、β-紫罗兰酮、3, 4-二甲基苯甲醛、2-己酮和叶醇等气味的识别过程, 且在不同气味中的识别过程中对于气味的运输能力有差异。