Pheromone Source Research Articles

Exploration-exploitation model of moth-inspired olfactory navigation.

Navigation of male moths towards females during the mating search offers a unique perspective on the exploration-exploitation (EE) model in decision-making. This study uses the EE model to explain male moth pheromone-driven flight paths. Wind tunnel measurements and three-dimensional tracking using infrared cameras have been leveraged to gain insights into male moth behaviour. During the experiments in the wind tunnel, disturbance to the airflow has been added and the effect of increased fluctuations on moth flights has been analysed, in the context of the proposed EE model. The exploration and exploitation phases are separated using a genetic algorithm to the experimentally obtained dataset of moth three-dimensional trajectories. First, the exploration-to-exploitation rate (EER) increases with distance from the source of the female pheromone is demonstrated, which can be explained in the context of the EE model. Furthermore, our findings reveal a compelling relationship between EER and increased flow fluctuations near the pheromone source. Using an olfactory navigation simulation and our moth-inspired navigation model, the phenomenon where male moths exhibit an enhanced EER as turbulence levels increase is explained. This research extends our understanding of optimal navigation strategies based on general biological EE models and supports the development of bioinspired navigation algorithms.

Bimodal alarm signals modulate responses to monomodal alarm signals in Camponotus modoc carpenter ants.

Distressed western carpenter ants, Camponotus modoc, produce alarm pheromone and substrate-borne vibrations. The alarm pheromone attracts nestmates but the effects of vibratory signals, or of bimodal pheromonal and vibratory signals, are not known. Worker ants of two Camponotus congeners reportedly stand still ("freeze") or run fast in response to engineered drumming vibrations inputted on plastic, but many responses to ant-produced vibratory signals on wood have not yet been investigated. Generally, orientating toward signalers under vertebrate predator attack seems maladaptive and not beneficial to ant colonies. We tested the hypotheses (1) that vibratory alarm signals cause freezing, rapid running but not attraction of nestmates, and (2) that bimodal alarm signals modulate responses to monomodal alarm signals, thereby possibly reducing predation risk. Laser Doppler vibrometry recordings revealed that the ants' vibratory signals readily propagate through ant nest lamellae, and thus quickly inform nest mates of perceived threats. With a speaker modified to record and deliver vibratory signals, we obtained drumming signals of distressed ants on a Douglas fir veneer, and bioassayed signal effects on ants in an arena with a suspended veneer floor. In response playback of vibratory signals, ants ran rapidly, or froze, but did not approach the vibratory signals. Exposed to alarm pheromone, ants frequently visited the pheromone source. However, concurrently exposed to both alarm pheromone and vibratory signals, ants visited the pheromone source less often but spent more time "frozen." The ants' modulated responses to bimodal signals seem adaptive but the reproductive fitness benefits are still to be quantified.

Studies on the response of normal and irradiated pink bollworm males towards pheromone source

Sterile Insect Technique (SIT) is the right eco-friendly method to overcome the pink bollworm Pectinophora gossypiella (Saunder) menace. In SIT attractiveness of released moths to their natural counterpart is most important as such this ability was examined in our study. For this, newly emerged five virgin female gamma irradiated with 0–250 Gy were used. These females were placed inside small plastic vial provided with aeration and suspended inside the delta traps by providing 10% honey solution. Traps were placed in the field during evening. Moth catches in each trap were counted and removed daily and these observations continued up to 5 days. In a same manner irradiated males were released separately inside the field cage to know its attractiveness to virgin female. The results indicated that attraction of male moths to irradiated virgin females decreased significantly with increasing doses of radiation i.e., at 200 and 250 Gy. The number of males captured per female was greatest on day 2nd due to its peak sexual activity, i.e., 25.60, 23.05, 19.45, 14, 9.4 and 5.9 moths at 0, 50, 100, 150, 150, 200, and 250 Gy, respectively. Gamma radiation also affected the irradiated males to find their natural mates at a higher dose; however, the maximum number of 5.30, 5.95 and 5.10 irradiated male moths were attracted to the natural pheromone secreted by female moths at 50, 100 and 150 Gy respectively, compared to the 6.80 moths at 0 Gy. The results on attractiveness of irradiated male moths towards virgin female-baited traps were considered a good measure of male competitiveness.

Prolonged Exposure to Plant Volatiles does not Significantly Affect Pban Expression and Mating Behavior in Diamondback Moth [Plutella Xylostella (Lepidoptera: Plutellidae)

Herbivorous insects use plant volatiles to locate hosts, find food, and identify oviposition sites to aid survival and reproduction. Plant volatiles not only regulate the synthesis and release of sex pheromones in insects, but also help them in the search and orientation of sources of sex pheromones. However, after prolonged exposure to plant volatiles, the changes mediating the mating behavior of diamondback moth (DBM) [Plutella xylostella (L.) (Lepidoptera: Plutellidae)] are unclear. DBMs treated with allyl isothiocyanate, a volatile from cruciferous vegetables, did not show improved rates of mating with a limited effect on mating rhythm. This treatment inhibited mating behaviors in 3-day-old DBMs and decreased mating duration in 5-day-old DBMs. After prolonged exposure to allyl isothiocyanate, the total mating duration of DBM was not significantly different from that after prolonged exposure to n-hexane (control). The longest mating duration after emergence in DBM after prolonged exposure to allyl isothiocyanate was delayed by 1day compared with exposure to n-hexane. Prolonged exposure to plant volatiles intensified the response behavior of DBM to sex pheromones. However, the amount of Z11-16: Ald, a major component of the sex pheromone blend exhibited no change in female pheromone glands. Pheromone biosynthesis activating neuropeptide gene (PBAN) was down-regulated in DBMs after prolonged exposure to plant volatiles. These findings suggest that prolonged exposure (6h) to plant-derived volatiles have little effect on the mating behavior of DBM. This study provides practical guidance for applying phytochemicals in pest control by regulating insect behavior.

The Trail-Following Communication in Stylotermes faveolus and S. halumicus (Blattodea, Isoptera, Stylotermitidae).

Stylotermitidae appear peculiar among all termites, feeding in trunks of living trees in South Asia only. The difficulty to collect them limits the ability to study them, and they thus still belong to critically unknown groups in respect to their biology. We used a combination of microscopic observations, chemical analysis and behavioural tests, to determine the source and chemical nature of the trail-following pheromone of Stylotermes faveolus from India and S. halumicus from Taiwan. The sternal gland located at the 5th abdominal segment was the exclusive source of the trail-following pheromone in both S. faveolus and S. halumicus, and it is made up of class I, II and III secretory cells. Using gas chromatography coupled mass spectrometry, (3Z)-dodec-3-en-1-ol (DOE) was identified as the trail-following pheromone which elicits strong behavioural responses in workers at a threshold around 10- 4 ng/cm and 0.1 ng/gland. Our results confirm the switch from complex aldehyde trail-following pheromones occurring in the basal groups to simpler linear alcohols in the ancestor of Kalotermitidae and Neoisoptera.

The Alarm Pheromone and Alarm Response of the Clonal Raider Ant

Ants communicate via an arsenal of different pheromones produced in a variety of exocrine glands. For example, ants release alarm pheromones in response to danger to alert their nestmates and to trigger behavioral alarm responses. Here we characterize the alarm pheromone and the alarm response of the clonal raider ant Ooceraea biroi, a species that is amenable to laboratory studies but for which no pheromones have been identified. During an alarm response, ants quickly become unsettled, leave their nest pile, and are sometimes initially attracted to the source of alarm, but ultimately move away from it. We find that the alarm pheromone is released from the head of the ant and identify the putative alarm pheromone as a blend of two compounds found in the head, 4-methyl-3-heptanone and 4-methyl-3-heptanol. These compounds are sufficient to induce alarm behavior alone and in combination. They elicit similar, though slightly different behavioral features of the alarm response, with 4-methyl-3-heptanone being immediately repulsive and 4-methyl-3-heptanol being initially attractive before causing ants to move away. The behavioral response to these compounds in combination is dose-dependent, with ants becoming unsettled and attracted to the source of alarm pheromone at low concentrations and repulsed at high concentrations. While 4-methyl-3-heptanone and 4-methyl-3-heptanol are known alarm pheromones in other more distantly related ant species, this is the first report of the chemical identity of a pheromone in O. biroi, and the first alarm pheromone identified in the genus Ooceraea. Identification of a pheromone that triggers a robust, consistent, and conserved behavior, like the alarm pheromone, provides an avenue to dissect the behavioral and neuronal mechanisms underpinning chemical communication.

Host odour alpha-pinene increases or reduces response of Ips avulsus (Coleoptera: Curculionidae: Scolytinae) to its aggregation pheromone, depending on separation of release points

Abstract Monoterpenes in the resin of host trees are important host-location and -selection signals for conifer-infesting bark beetles and can increase or reduce responses to aggregation pheromones. Research on this interaction has been largely limited to collocated release points of the semiochemicals; however, sources are often separated in nature. I performed a trapping experiment to investigate whether distance between semiochemical release points influences how host monoterpene alpha-pinene affects Ips avulsus (Eichhoff) (Coleoptera: Curculionidae) response to its aggregation pheromone (ipsdienol and lanierone). High release (8 g/day) of alpha-pinene from a pheromone-baited trap caused a reduction in catches, but the same release of alpha-pinene from 4 m away significantly increased catches relative to pheromone alone. A low release (0.06 g/day) of alpha-pinene with either arrangement had no effect. Hence, a host odour released at rates sufficient to deter I. avulsus responses to its pheromone may nevertheless enhance attraction if the release point is sufficiently displaced from the pheromone source. The result suggests that, for I. avulsus, the semiochemical alpha-pinene may influence host finding and close-range assessment of host suitability in different ways. Operational lure formulations for some species of bark beetle might be improved by separating pheromone and host odour components or by adding a displaced host odour device.

Characterizing Repellencies of Methyl Benzoate and Its Analogs against the Common Bed Bug, Cimex lectularius.

Bed bug infestations are on the rise globally, and remediation efforts are becoming more expensive and difficult to achieve due to rising insecticide resistance in the pest populations. This study evaluates Cimex lectularius behavior in the presence of attractive elements-aggregation pheromone or food source (human blood)-and the reported botanical repellent methyl benzoate (MB), several MB analogs, as well as the well-known insect repellent, N,N-diethyl-meta-toluamide (DEET). Utilizing EthoVision, a video tracking system, we now report that MB and several of its analogs exhibit strong spatial repellency against C. lectularius, with methyl 2-methoxybenzoate (M2MOB) and methyl 3-methoxybenzoate (M3MOB) exhibiting the strongest repellent effects. Further, our data showed that MB, M2MOB, M3MOB, and DEET exhibit repellency against a pyrethroid resistant strain of C. lectularius.

Event-driven daily activity recognition with enhanced emergent modeling

With the population aging, elderly health monitoring is triggering more studies on daily activity recognition as the fundamental of ambient assisted living. It is remarkable that activity recognition remains difficulties including how to adequately extract feature structure and settle the issue of activity confusion. To address these challenges, we propose a novel activity modeling method under the emergent paradigm with marker-based stigmergy and the directed-weighted network with additional context-aware information. In the modeling process, stigmergy is first introduced to aggregate the context information at the low level for generating activity pheromone trails, and then the constructed stigmergic trails are represented in form of directed-weighted network with distinguishability of individual pheromone source corresponding to location. The potential advantage is that the robust trails with distinguishable individual initial positions are feasible to supplement user’s daily habits and thus both inter-class and intra-class distances can be kept at acceptable levels. Experiments on Aruba demonstrates that the proposed emergent modeling method can effectively deal with the problems of feature extraction and activity ambiguity and achieve good classification performance.

Gradient tracking in mating yeast depends on Bud1 inactivation and actin-independent vesicle delivery.

The mating of budding yeast depends on chemotropism, a fundamental cellular process. Haploid yeast cells of opposite mating type signal their positions to one another through mating pheromones. We have proposed a deterministic gradient sensing model that explains how these cells orient toward their mating partners. Using the cell-cycle determined default polarity site (DS), cells assemble a gradient tracking machine (GTM) composed of signaling, polarity, and trafficking proteins. After assembly, the GTM redistributes up the gradient, aligns with the pheromone source, and triggers polarized growth toward the partner. Since positive feedback mechanisms drive polarized growth at the DS, it is unclear how the GTM is released for tracking. What prevents the GTM from triggering polarized growth at the DS? Here, we describe two mechanisms that are essential for tracking: inactivation of the Ras GTPase Bud1 and positioning of actin-independent vesicle delivery upgradient.

Diel Periodicity in Males of the Navel Orangeworm (Lepidoptera: Pyralidae) as Revealed by Automated Camera Traps.

Navel orangeworm, Amyelois transitella (Walker), is a key pest of walnuts, pistachio, and almonds in California. Pheromone mating disruption using timed aerosol dispensers is an increasingly common management technique. Dispenser efficiency may be increased by timing releases with the active mating period of navel orangeworm. Past work found that the peak time of sexual activity for navel orangeworm females is 2 h before sunrise when temperatures are above 18°C. Inference of male responsiveness from data collected in that study was limited by the necessity of using laboratory-reared females as a source of sex pheromone emission to attract males and the inherent limitations of human observers for nocturnal events. Here we used camera traps baited with artificial pheromone to observe male navel orangeworm mating response in the field over two field seasons. Male response to synthetic pheromone exhibited diel patterns broadly similar to females, i.e., they were active for a brief period of 2–3 h before dawn under summer conditions and began responding to pheromone earlier and over a longer period of time during spring and fall. But contrary to the previous findings with females, some males were captured at all hours of the day and night, and there was no evidence of short-term change of pheromone responsiveness in response to temperature. Environmental effects on the response of navel orangeworm males to an artificial pheromone source differ in important ways from the environmental effects on female release of sex pheromone.

Development of Methods for the Use of Aphid Alarm and Mite Aggregation Pheromones

The purpose of this work was to develop effective methods of protecting fruit crops based on the use of aphid alarm and mite aggregation pheromones. The study was conducted in 2020-2021 on a private farm in the Krasnodar Territory. Laboratory studies were carried out on two types of aphids: Aphis pomi Deg. and Myzus cerasi F. with the use of trans-beta-farnesene where crushed aphids of the tested species served as the source of the alarm pheromone, and insects without treatment were used as a control group. Field tests were carried out on registered trees with aphid colonies up to 10% of shoots in the crown, and mite colonies of 15-23 specimens/ leaf. Significant differences in the types of ethological reactions of apple and cherry aphids to trans-beta-farnesene were observed. In A. pomi, the predominant type was the twitching of the body during the initial period of exposure to the semiochemical. In cherry aphids, only one type of behavioral reaction to the alarm pheromone was noted, namely leaving the feeding site. The results of testing trans-beta-farnesene compositions with preparations based on biorational active substances, Phytoverm CE (2 g/l), and experimental insecticides based on coriander essential oil indicate the prospects of using the aphid alarm pheromone (trans-beta-farnesene) to increase the effectiveness of anti-aphid insecticides. Similar results were obtained in tests of trans-nerolidol, the pheromone used for aggregation of red spider mites in a composition with the Apollo, SC acaricide (500 g/l).

Release of moth pheromone compounds from Nicotiana benthamiana upon transient expression of heterologous biosynthetic genes

BackgroundUsing genetically modified plants as natural dispensers of insect pheromones may eventually become part of a novel strategy for integrated pest management.ResultsIn the present study, we first characterized essential functional genes for sex pheromone biosynthesis in the rice stem borer Chilo suppressalis (Walker) by heterologous expression in Saccharomyces cerevisiae and Nicotiana benthamiana, including two desaturase genes CsupYPAQ and CsupKPSE and a reductase gene CsupFAR2. Subsequently, we co-expressed CsupYPAQ and CsupFAR2 together with the previously characterized moth desaturase Atr∆11 in N. benthamiana. This resulted in the production of (Z)-11-hexadecenol together with (Z)-11-hexadecenal, the major pheromone component of C. suppressalis. Both compounds were collected from the transformed N. benthamiana headspace volatiles using solid-phase microextraction. We finally added the expression of a yeast acetyltransferase gene ATF1 and could then confirm also (Z)-11-hexadecenyl acetate release from the plant.ConclusionsOur results pave the way for stable transformation of plants to be used as biological pheromone sources in different pest control strategies.

The Effect of Wind Speed on Male Potato Aphid, Macrosiphum euphorbiae, Responses to Primary Host Plant Volatiles and Female Sex Pheromone.

Simple SummaryWe demonstrate that male potato aphids respond more to a combination of volatiles from the host plant on which the species overwinters and the female sex pheromone than to the host plant alone. In both cases, the level of response declines as wind speed increases, but the higher attraction to the combined odour sources is maintained. These findings are discussed within the context of mate location by male aphids, which are insects that have little control over flight direction.In fall, alate males of the potato aphid, Macrosiphum euphorbiae (Thomas), migrate from their summer (secondary) host plants, such as potatoes, to primary host plants, such as roses, where they mate with wingless oviparae who produce the overwintering egg stage. Males are weak fliers and generally walk towards a pheromone source under windy conditions, so we tested the hypothesis that upwind walking behaviour in response to wind velocity would be affected by the volatile cues present. We compared male responses to the odour of a rugosa rose cutting alone and to the combination of host plant volatiles and the female sex pheromone under a range of wind speeds in a laboratory walking bioassay. The proportion of males responding decreased as the wind speed increased, but at all wind velocities, the responses to the combined odours were higher than to the host plant alone. However, at any given wind velocity, the speed at which responding aphids moved was not influenced by the odour source. These findings support the idea that host plant volatiles serve as long-distance cues for males and that the female sex pheromone is used once on the host plant.

IDENTIFICATION OF PUTATIVE MUP DURING ESTRUS PERIOD IN FEMALE RAJAPALAYAM BREED DOG BY MALDI-TOF ANALYSIS

A low molecular mass protein (range from 17 to 20 kDa) found in urine, faeces, saliva, glandular secretions, and other pheromone sources has been discovered as a Ligand-carrier (i.e., pheromone carrier) involved in chemical-communication among mammals. The present study examines whether a low molecular protein can be found in the urine of a female Rajapalayam dog and, if so, whether its expression varies during the estrous cycle. SDS-PAGE and MALDI-TOF MS were used to detect estrus-specific urinary proteins in urine samples taken from eight female dogs. The total urinary protein level was substantially greater (p< 0.05) in the estrus phase than in the other phases. The results of SDS-PAGE analysis revealed seven different molecular masses of proteins across three phases of estrous cycle, ranging from 13 to 99 kDa. The intensity of the 17 kDa molecular mass protein was significantly higher during estrus phase and incredibly reduced during postestrus, we speculated that it may be an ovulation-indicating protein. The 17 kDa band was digested in-gel with trypsin before being analysed using MALDI-TOF/MS and MASCOT. MALDI-TOF MS and MASCOT searches revealed the presence of MUPs (major urinary proteins) in the 17 kDa band. The present study concludes that MUPs are exclusively expressed in large amounts during the estrus phase. They might transport and prolong the longevity of volatiles in scented sites, thereby providing olfactory cues (i.e. attraction towards males). In addition, the specific expression of MUPs in Rajapalayam dog can be exploited to detect estrus.

Effects of floor pattern on flight behaviour of the smaller tea tortrix, Adoxophyes honmai, during orientation flight in a sex pheromone plume

AbstractInsects control their flight toward a distant odour source by integrating multimodal sensory information, such as olfactory and visual information. Control of flight speed in orientation flight toward an odour source using visual patterning below has been observed in many species of moths. However, there are few reports about moth flight behaviour over solid‐coloured floors. To examine, which visual stimuli affect flight behaviour of moths, male smaller tea tortrix (Adoxophyes honmai) were released in a pheromone plume over two striped floors (longitudinal and transverse stripes) and two unpatterned floors (solid white and solid black). Flight behaviours were videotaped, and upwind flight speed, height (altitude) and the number of backward movements moths made as they approached the pheromone source were determined. Male moths significantly increased mean and maximum upwind flight speed over longitudinal stripes relative to their speed over transverse stripes. Their speed over a solid black floor was the fastest of all floor patterns tested. As males approached the pheromone source, their mean upwind speed decreased significantly over all floor patterns, except for the black floor. Fewer moths made backward movements over the black floor compared with the other three floors. In addition, male moths flew significantly higher over the white floor than over the other three floors, while 60–40 cm from the pheromone source. This is the first time that differences in moth flight behaviour over two patternless floors have been reported. These results suggest that orientation flight behaviour of male moths is affected not only by visual patterns, but also by the reflectance or reflected wavelength spectrum of the floor.

Olfactory dysfunction and potential mechanisms caused by volatile organophosphate dichlorvos in the silkworm as a model animal

Volatile pesticides impair olfactory function in workers/farmers and insects, but data on molecular responses and mechanisms are poorly understood. This study aims to reveal the mechanisms of olfactory dysfunction in the silkworm after exposure to volatile dichlorvos. Our results demonstrated that acute exposure for 12 h significantly reduced electroantennogram responses, and over 62.50% of the treated male moths cannot locate the pheromone source. Transcriptional and proteomic responses of the antennae and heads were investigated. A total of 101 differentially expressed genes (DEGs) in the antennae, 138 DEGs in the heads, and 43 differentially expressed proteins (DEPs) in the heads including antennae were revealed. We discovered that upregulations of Arrestin1 and nitric oxide synthase1 (NOS1) may inhibit cyclic nucleotide-gated channels and hinder calcium influx in the antennae. In the central nervous systems (CNS), downregulations of tyrosine hydroxylase (TH) and tyrosine decarboxylase (TDC) may inhibit olfactory signal transduction by reducing the second messenger biosynthesis. Meanwhile, an abnormal increase of brain cell apoptosis was revealed by Annexin V-mCherry staining, often leading to persistent neurologic impairment. Taken together, this study highlighted olfactory dysfunction caused by dichlorvos, which may provide a novel perspective for understanding the toxicity mechanism of volatile pesticides in other organisms.

Pheromone binding protein is involved in temporal olfactory resolution in the silkmoth

SummaryMale moths utilize spatio-temporal female sex pheromone information to orient toward conspecific females. Pheromones are distributed as discontinuous plumes owing to air turbulence; thus, efficient tracking of intermittent stimuli is expected to require a high temporal resolution. Here, using pheromone binding protein (BmPBP1)-knockout silkmoths, we showed that a loss of functional PBP lowered the temporal sensory resolution of male antennae. This altered temporal resolution resulted in significantly reduced straight walking and longer turning behavior, which respectively occurred when males detected and lost contact with pheromones, indicating that temporal resolution was also lowered at the behavioral level. BmPBP1-knockout males required significantly longer time than wild-type males in locating pheromone sources and female moths. Our results suggest that BmPBP1 plays a critical role in determining olfactory response kinetics. Accordingly, high temporal olfactory and behavioral resolutions, as shaped by PBP, are essential for tracking pheromone plumes and locating females efficiently.

Staphylococcus pasteuri (BCVME2) Resident in Buffalo Cervical Vaginal Mucus: A Potential Source of Estrus-Specific Sex Pheromone(s)

Mammals have microbes resident in their reproductive tract, some of which can be pathogenic while others may play a role in protecting the tract from infection. Volatile compounds play a role as sex pheromones that attract males for coitus during female estrus or heat. It is likely that these compounds themselves are secondary metabolites of bacterial flora resident in the vagina. In order to substantiate this hypothesis, bacteria were isolated from cervico-vaginal mucus (CVM) of buffalo during various phases of the estrous cycle and identified, using morphological, biochemical and molecular characteristics, asBacillusduring preestrus and diestrus, and as Staphylococcusduring all three phases of the estrous cycle. Populations of Staphylococcus differed between different phases of the estrous cycle, the predominant forms being S. warneri (BCVMPE1_1) during preestrus, S. pastueri(BCVME2) during estrus andS. epidermis (BCVMDE3) during diestrus. Mice were used as chemosensors to differentiate the estrus-specific S. pasteuri(BCVME2) from the others. Chemical analysis showed that S. pasteuri(BCVME2) produced acetic, propanoic, isobutyric, butyric, isovaleric and valeric acids. In addition, it was shown that S. pasteuri(BCVME2) volatiles influenced the sexual behaviors, flehmen and mounting, of the bull. Thus, S. pasteuri(BCVME2) is a potential source of vaginal pheromone(s) during estrus in buffalo.

TMEM16A and TMEM16B Modulate Pheromone-Evoked Action Potential Firing in Mouse Vomeronasal Sensory Neurons

The mouse vomeronasal system controls several social behaviors. Pheromones and other social cues are detected by sensory neurons in the vomeronasal organ (VNO). Stimuli activate a transduction cascade that leads to membrane potential depolarization, increase in cytosolic Ca2+ level, and increased firing. The Ca2+-activated chloride channels TMEM16A and TMEM16B are co-expressed within microvilli of vomeronasal neurons, but their physiological role remains elusive. Here, we investigate the contribution of each of these channels to vomeronasal neuron firing activity by comparing wild-type (WT) and knock-out (KO) mice. Performing loose-patch recordings from neurons in acute VNO slices, we show that spontaneous activity is modified by Tmem16a KO, indicating that TMEM16A, but not TMEM16B, is active under basal conditions. Upon exposure to diluted urine, a rich source of mouse pheromones, we observe significant changes in activity. Vomeronasal sensory neurons (VSNs) from Tmem16a cKO and Tmem16b KO mice show shorter interspike intervals (ISIs) compared with WT mice, indicating that both TMEM16A and TMEM16B modulate the firing pattern of pheromone-evoked activity in VSNs.