Conspecific odor detection by the male broad-headed skink, Eumeces laticeps: effects of sex and site of odor source and of male reproductive condition

Olfactory stimuli are sufficient for detection and discrimination of sex of conspecific lizards by the male broad-headed skink, Eumeces laticeps, a member of a large group of lizards with pronounced chemosensory abilities, the Autarchoglossa. The capacity of male broad-headed skinks to detect conspecific odors was assessed by measuring tongue extrusion rates in response to odor stimuli presented on moist cotton applicators. Tongue-flick rates of postreproductive males were significantly higher for cloacal odors of postreproductive conspecifics of both sexes than to distilled water and higher to female than male odors over the initial 20- and 60-sec intervals. In a second experiment using testosterone-treated males and estrogen-injected females, testosterone-treated males emitted significantly more tongue flicks to female cloacal odors than to the other stimuli, and two males bit applicators bearing male odors. Testosterone did not affect reaction to male cloacal odors, but markedly increased tongue-flick rates in response to cloacal odors of estrogen-treated females. Postreproductive males also responded to female, but not male, skin odors at a significantly higher rate than to water. Possible sources and presumed adaptive significance of conspecific odors are discussed.     

Plasmodium sex determination and transmission to mosquitoes

In order to be transmitted by their mosquito vector, malaria parasites undergo sexual reproduction, which occurs between specialized male and female parasites (gametes) within the blood meal in the mosquito. Nothing was known about how Plasmodium determines the sex of its gametocytes (gamete precursors), which are produced in the vertebrate host. Recently, erythropoietin, the vertebrate hormone controlling erythropoiesis in response to anaemia, was implicated in Plasmodium sex determination in animal models of malaria. This review examines the available information and addresses the relevance of such a sex determining mechanism for Plasmodium falciparum transmission to mosquitoes, with special reference to low gametocytaemias.     

Performance of mice in an automated olfactometer: odor detection, discrimination and odor memory

Mice were trained on a variety of odor detection and discrimination tasks in 100- or 200-trial sessions using a go, no-go discrete trials operant conditioning procedure. Odors, presented for 1 s on each trial, were generated by an air dilution olfactometer (for threshold tests) and an easily constructed eight-channel liquid dilution unit (for two- and multiple-odor discrimination tasks). Mice rapidly acquired the operant task and demonstrated excellent stimulus control by odor vapors. Their absolute detection threshold for ethyl acetate was similar to that obtained with rats using similar methods. They readily acquired four separate two-odor discrimination tasks and continued to perform well when all eight odors were presented in random order in the same session and when reinforcement probability for correct responding was decreased from 1 to 0.5. Memory for these eight odors, assessed under extinction after a 32 day rest period, was essentially perfect. Time spent sampling the odor on S+ and S- trials was highly correlated with response accuracy. When accuracy was at chance levels (e.g. initial trials on a novel task), stimulus sampling time on both S+ and S- trials was approximately 0.5-0.7 s. As response accuracy increased, sampling time on S+ trials tended to increase and remain higher than sampling time on S- trials.     

Influence of short time exposure to an insect growth regulator, hexaflumuron, on mortality and adult emergence of vector mosquitoes.

Hexaflumuron, an insect growth regulator (IGR), was found to greatly affect the development of immatures and emergence of adults of three species of vector mosquitoes, Culex quinquefasciatus, Aedes aegypti and Anopheles stephensi, when larvae were subjected to short time exposure of < or = 1 h. This IGR could completely prevent adult emergence even at a minimum exposure time of 10 min at 0.001, 0.01 and 0.1 mg/l. On treatment, larval and pupal mortality as well as varying degrees of morphogenetic abnormalities were induced in immatures and adults of the three species. Four weeks of control achieved in a slow moving sullage canal breeding Culex quinquefasciatus indicates that this IGR can be of use in such breeding habitats.     

Chronotype,gender, and time for sex

The study aimed at testing chronotype and gender differences in the time of day when humans feel the greatest need for sex and the time of day they actually undertake sexual activity. A Polish sample of 565 participants aged between 18 and 57 was tested. In females, regardless of chronotype, the greatest need for sex occurred between 18:00 and 24:00, but a secondary peak appeared only in morning types at 6:00–9:00. In males, the greatest need for sex occurred either in the morning or evening hours: in evening types at 9:00–12:00 and 18:00–3:00; in neither types at 6:00–9:00 and 18:00–24:00; in morning types at 6:00–12:00 and 18:00–24:00. Considering time of day when subjects were undertaking sexual activity most frequently, this appeared between 18:00 and 24:00 for all the participants, and prolonged until 3:00 at night in evening type males. Morningness preference was more strongly related to the timing of need for sex than to the timing of actual sexual activity (r?=??0.275 vs. r?=??0.174), while the timing of desire and the timing of sexual activity were positively, but moderately related (r?=?0.320).     

From odor molecules to plume tracking: an interdisciplinary, multilevel approach to olfaction in stomatopods

Like many marine crustaceans, mantis shrimp rely on their senseof smell to find food, mates, and habitat. In order for olfactionto function, odorant molecules in the surrounding fluid mustgain access to the animal's chemosensors. Thus fluid motionis important for olfaction, both in terms of the large scalefluid movements (currents, waves, etc.) that advect the odorantsto the vicinity of the sensors, and the small-scale viscositydominated flows that determine odorant access to the surfaceof the sensor. In order to understand how stomatopods interprettheir chemical environment, I investigated how stomatopod chemosensorymorphology and the movement of the structures bearing the chemosensorsaffect fluid access to the sensor surface in Gonodactylaceusmutatus. Preliminary results from new directions are presented,including mathematical modeling of molecular flux at the sensorsurface, field studies of the effects of ambient flow on odorsampling behavior, and flume experiments testing the abilityof stomatopods to trace odor plumes. Finally, I show how theuse of multiple techniques from several disciplines leads tonew ideas about the functional morphology of stomatopod antennules.     

Beyond odor discrimination: demonstrating individual recognition by scent in Lemur catta

The current study demonstrates, for the first time, the occurrence of olfactory individual recognition in a nonhuman primate species. The empirical demonstration of recognition systems requires 1) a set of cues produced by the sender (expression component), 2) the perception of these cues by the receiver (perception component), and 3) a functional response by the receiver (action component). On the basis of this framework, we analyzed by gas chromatography 35 brachial secretions collected from 10 males of Lemur catta. Moreover, we performed habituation/discrimination tests to demonstrate the perception component, and we designed a specific bioassay, based on territorial competition, to highlight a functional response to individual odors. We demonstrated that recognition of conspecific odors goes beyond the perception of cues other than individuality (familiarity, kin, season, age, and rank) and that the receiver actually forms a mental representation of a specific individual by its scent.     

不同性别和年龄的大仓鼠对黄鼬气味的反应

将雌性成体和雌雄亚成体大仓鼠 (Cricetulustriton)长期 (4周 )暴露给过量的黄鼬 (Mustelasibirica)肛腺分泌物 ,观察其行为和生理状态的变化 ,并通过与我们以前有关黄鼬气味对成年雄鼠影响的研究结果进行比较 ,表明黄鼬气味对不同性别和不同年龄大仓鼠的胁迫效应和生殖抑制存在差异。发现黄鼬气味对雌性大仓鼠的影响较雄性小 ,对亚成体的影响较成体小 ,这与雌性和未成年动物对各种胁迫因素的反应更敏感的普遍现象相反。在成年鼠中 ,雌雄鼠的攻击行为都受到黄鼬气味的抑制 ;但天敌气味使雌性的胁腺膨大 ,对胁腺标记和肾上腺大小无影响 ;成年雄鼠的肾上腺膨大 ,胁腺萎缩 ,标记减少。在亚成体中 ,除了雄性胁腺受到抑制(与成年雄鼠相同 )外 ,雌雄鼠的肾上腺和雌性的胁腺未受影响。亚成体实验鼠的体重都比对照组低 ,但成年鼠的体重未受影响。另外 ,与以往对其它鼠类的研究结果一致 ,天敌气味并不影响成年鼠的生殖器官 ,却抑制了未成年雄鼠的附睾和未成年雌鼠的子宫。这些差异可能和生理基础的性二态以及可能面临的被捕食风险大小有关     

Molecular scatology: the use of molecular genetic analysis to assign species, sex and individual identity to seal faeces

Seals and commercial fisheries are potential competitors for fish and cephalopods. Research into the diet of British seal species has been based on conventional dietary analyses, but these methods often do not allow assignment of species identity to scat samples. We present a protocol for obtaining DNA from seal scat (faecal) samples which can be used in polymerase chain reactions to amplify both nuclear and mitochondrial DNA. This can provide a method of identifying the species, sex and individual identity of the seal, from a particular scat sample. Combined with conventional dietary analyses these techniques will allow us to assess sources of variation in seal diet composition.
Scat samples have been collected from intertidal haul-out sites around the inner Moray Firth, north-east Scotland. We have assessed methods to extract and purify faecal DNA, a combination of DNA from the individual seal, prey items, and gut bacteria, for use in PCR. Controls using faecal and blood samples from the same individual have enabled microsatellite primer sets from four pinniped species to be tested. Approximately 200 scat samples have been examined for species identity and individual matches. This study will provide essential information for the assessment of interactions between seals and commercial or recreational fisheries.     

Odor and affect: individual differences in the impact of odor on liking for places, things and people

This paper provides evidence of substantial individual differences in the affective importance of odors, and offers initial validation for an eight-item scale of the impact of odor (AIO) on liking for people, places, foods and cosmetic/health products. In study 1, 116 American college students and 336 Flemish Belgian college students completed the AIO along with other measures of reactions to odors and to commercial products designed to mask body odors. There were substantial individual differences in AIO scores, but means were similar for males and females, and for US and Belgian respondents. Higher AIO scores were associated with more odor-mediated memory, more attention to odors and more liking or disliking for odors as a function of their association with liked and disliked persons. AIO scores were not related to preference for toiletries with artificial scents, to use of products to mask natural body odors, or to disgust sensitivity. In study 2, AIO scores were strongly related to a measure of evaluative conditioning (a form of Pavlovian associative learning) in the laboratory, using liked and disliked odors as unconditioned stimuli and pictures of faces as conditioned stimuli.     

Increased behavioral and neuronal sensitivity to sex pheromone after brief odor experience in a moth

Plasticity in the response to stimuli related to food and oviposition cues is well documented in insects. However, responses to cues related to reproduction, for example, sex pheromones, are considered to be innate and thus not affected by experience. Here we show that brief preexposure to sex pheromones, without ensuing reward, lowers the threshold for behavioral response and augments the sensitivity in antennal lobe interneurons to pheromone compared with naive male moths. Thus, the sex pheromone system in insects can be modulated by experience. In addition, we show that the behavioral attraction to sex pheromone increases after preexposure in a time-dependent manner: a short-term effect, possibly a form of sensitization, and a long-term effect after more than 24 h. The behavioral long-term effect is paralleled by an increase in sensitivity of interneurons in the primary olfactory center, whereas the peripheral olfactory system does not change its sensitivity. We hypothesize that short-term sensitization to sex pheromone serves as a kind of alert system, whereas the long-term effect improves male performance when reproductively active females are present.     

Dispersal by gray ratsnakes: Effects of sex,age and time

Dispersal is one of the most fundamental components of ecology. Dispersal is also particularly relevant in an era of unprecedented habitat loss and climate change. We used a unique dataset to examine dispersal in gray ratsnakes (Pantherophis spiloides). Over a decade, we marked and released >1,500 hatchlings while monitoring the population of ratsnakes over a large area (≈1,900 ha). We tested the hypotheses that dispersal should be (a) largely restricted to within the local population given previous genetic evidence of limited gene flow at greater distances and (b) male biased because male gray ratsnakes are under strong sexual selection. We recaptured 69 gray ratsnakes that had been marked as hatchlings after periods ranging from 1 day to 11 years. We found that dispersal distance increased with time, but was not significantly sex-biased, and that gray ratsnakes are extremely faithful to their communal hibernacula (only 2.8% of 497 juvenile and adult ratsnakes captured at least twice at communal hibernacula changed sites between years). Thus, dispersal is largely limited to the period from hatching until an individual joins a communal hibernaculum. Based on the spatial patterns of dispersal we observed, the most plausible explanation for dispersal is that hatchling ratsnakes disperse from their natal site to join a neighboring communal hibernaculum. Our study yielded the most reliable data on dispersal distances from birth by a snake to date.     

Tolerance to individual and joint effects of arsenic and Bacillus thuringiensis subsp,israelensis or Lysinibacillus sphaericus in Culex mosquitoes

Arsenic contamination of global water supplies has come to the forefront in policy decisions in recent decades. However, the effects of arsenic on lower trophic levels of insects inhabiting contaminated ecosystems are not well understood. One approach to document both acute and sublethal effects of toxicants like arsenic is to assay them in combination with microbial pathogens to evaluate shifts in survival curves of the test organisms. Larvae of Culex quinquefasciatus and Culex tarsalis were reared in water containing 0 or 1 000μg/L of arsenate or arsenite. Fourth instars were then exposed to a range of doses of Bacillus thuringiensis subsp, israelensis （Bti） or Lysinibacillus sphaericus （Ls）, with shifts in lethal concentrations determined. Arsenic accumulation in 4th instars was also quantified, and a relative growth index （RGI） calculated for the treatments and compared to controls. Larvae of both species accumulated between 4 447 ± 169 ng As/g and 6 983 4- 367 ng As/g, though RGI values indicated accumulation did not affect growth and development. In all cases, the LC50＇s and LC90＇s of Cx. quinquefasciatus exposed jointly with arsenic and Bti/Ls were higher than Cx. tarsafis. Cx. tarsafis reared in arsenite showed a significant reduction in their Bti LC90 values compared to the control, indicating a sublethal effect of Bti. When exposed jointly with Ls, arsenite was more toxic than arsenate in Cx. tarsalis. Overall, these results indicate tolerance of these Culex species to arsenic exposures, and why this may occur is discussed.     

Chronic exposure of cat odor enhances aggression,urinary attractiveness and sex pheromones of mice

To test whether predator odor exposure negatively affects the behavior of prey, we exposed three groups of male house mice (Mus musculus) to the odors of cat (Felis catus) urine, rabbit (Oryctolagus cuniculus) urine and water (control), respectively, for consecutive 58 days and investigated how the treatments affected the response, aggressiveness, dominance, urinary attractiveness to females and pheromone composition of male mice. Compared to mice exposed to rabbit urine or water, those exposed to cat odor did not show any response habituation to the cat odor and became more aggressive, increased mark urine production and were more attractive to females when the latter were tested with their urine. Furthermore, gas chromatography coupled with mass spectrometry analysis revealed coincident elevations of the well-known male pheromones, E,E-α-farnesene, E-β-farnesene, R,R-dehydro-exo-brevicomin or S-2-sec-butyl-dihydrothiazole. In addition, rabbit urine exposure increased urinary attractiveness to females and pheromonal levels of the males in comparison with the mice exposed to water. This could be related to olfactory enrichment of heterospecific chemosignals, suggesting that predator odors were more beneficial. In light of these anti-intuitional findings in the chemical interaction between cats and mice, we conclude that predator odor affects prey more profoundly than previously believed and that its impact may not always be negative.     

Influences of age and sex on a microencapsulated odor memory test

While the influences of such variables as age and sex are well established for most standardized tests of odor identification and detection, this is not the case for tests of odor memory. In this study, 231 non-smoking men and women, ranging in age from 10 to 68 years, were administered a standardized 12-item match-to-sample microencapsulated odor memory test (OMT). Anosmics were excluded from the study. Each participant was asked to smell a target odorant after its release from a microencapsulated odorant pad and then, after a delay interval of 10, 30 or 60 s, to pick the target from a similarly presented set of four odors, three of which were foils. Backward counting by threes was required during the delay intervals in an effort to minimize semantic rehearsal. Overall OMT scores were higher for women than for men, and decreased, in each sex, as a function of age in a manner similar to the age-related decline observed in tests of odor identification and detection. Performance did not change as a function of delay interval. A significant correlation between the overall OMT test scores and scores on the University of Pennsylvania Smell Identification Test was observed for women, but not for men, in accord with the notion that women may be more likely to employ semantic cues in their strategies to remember odors. The findings are discussed in light of the complexities of the construct of odor memory.     

Indole and 3-chloroindole: The source of the disagreeable odor of Hygrophorus paupertinus

The odor emanating from sporocarps of Hygrophorus paupertinus is disagreeable and fecal-like. Solid phase microextraction (SPME) and analysis by gas chromatography-mass spectrometry (GC-MS) showed 1-octen-3-ol, indole and 3-chloroindole were responsible for the odor. This is the first case in which 3-chloroindole has been identified from a terrestrial organism.