Attractive Odor Research Articles

The Orbitofrontal Cortex Is Required for Learned Modulation of Innate Olfactory Behavior.

Animals have evolved innate responses to cues including social, food, and predator odors. In the natural environment, animals are faced with choices that involve balancing risk and reward where innate significance may be at odds with internal need. The ability to update the value of a cue through learning is essential for navigating changing and uncertain environments. However, the mechanisms involved in this modulation are not well defined in mammals. We have established a new olfactory assay that challenges a thirsty mouse to choose an aversive odor over an attractive odor in foraging for water, thus overriding their innate behavioral response to odor. Innately, mice prefer the attractive odor port over the aversive odor port. However, decreasing the probability of water at the attractive port leads mice to prefer the aversive port, reflecting a learned override of the innate response to the odors. The orbitofrontal cortex (OFC) is a fourth-order olfactory brain area, involved in flexible value association, with behaviorally relevant outputs throughout the limbic system. We performed optogenetic and chemogenetic silencing experiments that demonstrate the OFC is necessary for this learned modulation of innate aversion to odor. Further, we characterized odor evoked c-fos expression in learned and control mice and found significant suppression of activity in the bed nucleus of the stria terminalis, lateral septum, and central and medial amygdala. These findings reveal that the OFC is necessary for the learned override of innate behavior and may signal to limbic structures to modulate innate response to odor.

Binding characteristics and structural dynamics of two general odorant-binding proteins with plant volatiles in the olfactory recognition of Glyphodes pyloalis

Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is the most destructive pest, causing severe damage to mulberry production in China's sericulture industry. The insecticide application in mulberry orchards poses a significant risk of poisoning to Bombyx mori. Shifting from insecticides to odor attractants is a beneficial alternative, but not much data is available on the olfactory system of G. pyloalis. We identified 114 chemosensory genes from the antennal transcriptome database of G. pyloalis, with 18 odorant-binding protein (OBP) and 17 chemosensory protein (CSP) genes significantly expressed in the antennae. Ligand-binding assays for two antennae-biased expressed general odorant-binding proteins (GOBPs) showed high binding affinities of GOBP1 to hexadecanal, β-ionone, and 2-ethylhexyl acrylate, while GOBP2 exhibited binding to 4-tert-octylphenol, benzyl benzoate, β-ionone, and farnesol. Computational simulations indicated that van der Waal forces predominantly contributed to the binding free energy in the binding processes of complexes. Among them, Phe12 of GOBP1 and Phe19 of GOBP2 were demonstrated to play crucial roles in their bindings to plant volatiles using site-directed mutagenesis experiments. Moreover, hexadecanal and β-ionone attracted G. pyloalis male moths in the behavioral assays, while none of the candidate plant volatiles significantly affected female moths. Our findings provide a comprehensive understanding of the molecular mechanisms underlying olfactory recognition in G. pyloalis, setting the groundwork for novel mulberry pests control strategies based on insect olfaction.

Morphological characterization and distribution of antennal sensilla of Spodoptera frugiperda (Lepidoptera: Noctuidae) using scanning electron microscopy.

The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a globally significant agricultural pest, causing severe damage to corn production in China. Chemical odor-based trapping is a major approach for FAW control, making it essential to understand the FAW antennal sensillum types to enhance development of effective chemical odor attractants. In this study, we comprehensively examined the antennal sensilla types of FAW, identifying eight types and two subtypes, including Böhm's bristles, sensilla trichoidea, sensilla chaetica (I and II), sensilla coeloconica, sensilla styloconica, sensilla squamiformia (I and II), sensilla auricillica, and sensilla basiconica. Sensilla chaetica II, and sensilla squamiformia II are reported for the first time for FAW in this study. Detailed low-voltage field emission scanning electron microscope (LVSEM) images and descriptions are provided for each sensillum type. This study provides the morphological information to aid in conducting antennal sensillum neurophysiological tests on FAW. RESEARCH HIGHLIGHTS: The types of sensilla of fall armyworm were examined, identifying eight types and two subtypes, including Böhm's bristles, sensilla trichoidea, sensilla chaetica (I and II), sensilla coeloconica, sensilla styloconica, sensilla squamiformia (I and II), sensilla auricillica, and sensilla basiconica. Detailed low-voltage field emission scanning electron microscope images and descriptions were provided for each sensillum type.

Multimodal interactions in Stomoxys navigation reveal synergy between olfaction and vision

Stomoxys flies exhibit an attraction toward objects that offer no rewards, such as traps and targets devoid of blood or nectar incentives. This behavior provides an opportunity to develop effective tools for vector control and monitoring. However, for these systems to be sustainable and eco-friendly, the visual cues used must be specific to target vector(s). In this study, we modified the existing blue Vavoua trap, which was originally designed to attract biting flies, to create a deceptive host attraction system specifically biased toward attracting Stomoxys. Our research revealed that Stomoxys flies are attracted to various colors, with red proving to be the most attractive and selective color for Stomoxys compared to the other colors tested. Interestingly, our investigation of the cattle–Stomoxys interaction demonstrated that Stomoxys flies do not prefer a specific livestock fur color phenotype, despite variation in the spectrum. To create a realistic sensory impression of the trap in the Stomoxys nervous system, we incorporated olfactory cues from livestock host odors that significantly increased trap catches. The optimized novel polymer bead dispenser is capable of effectively releasing the attractive odor carvone + p-cresol, with strong plume strands and longevity. Overall, red trap baited with polymer bead dispenser is environmentally preferred.

Volatile chemical cues emitted by an agricultural companion plant (Cnidium monnieri) attract predatory lacewings (Chrysoperla sinica)

Plant volatiles play an important role in the recruitment of arthropod natural enemies and are widely used in foraging by many species. Therefore, identification of plants that release useful volatile organic compounds (VOCs) for influencing natural enemies and for the control of pests can be helpful in conservation biological control. Cnidium monnieri (L.) can convene many predatory enemies (lady beetles, hoverflies, lacewings) as a functional plant. The Chrysoperla sinica (Tjeder) is a dominant generalist predator, and can control the population of various pests in agricultural fields. However, how C. monnier recruits C. sinica and the chemical association between them is unknown. In this study, we tested the attractiveness of odor released by flowers and leaves of C. monnieri to C. sinica in Y-tube olfactometer. Next, we conducted solid phase microextraction (SPME), gas chromatography-mass spectrometry (GC–MS), and electrophysiological studies (EAG) to analyze the compounds and identified the volatile components which have effects on C. sinica. We also used a Y-tube olfactometer to verify the effectiveness of the volatile components on C. sinica under laboratory conditions. In olfactometer trials, C. sinica adults preferred flowers compared with leaves and fresh air. In GC–MS and electroantennography trials, seventy-six volatiles extracted from C. monnieri, twelve antenna-active components in three different concentrations (0.1 μg/mL, 1 μg/mL, 10 μg/mL) were detected for electroantennography. In the last behavioral identification assays, four synthetic compounds (10 μg/mL) had significant attractiveness of adult C. sinica antenna (i.e., γ-terpinene, trans-β-Ocimene, nerolidol, (Z)-3-Hexen-1-ol). These studies suggest that there is a chemical association between natural enemies C. sinica and the functional plant C. monnieri. This study provides a basis that can facilitate the production and application of attracting natural enemy and development and application of enhancing attractants.

To attract a moth: Wind tunnel and field testing of plant odor and light stimuli and their combination for Ostrinia nubilalis

AbstractThe European corn borer, Ostrinia nubilalis (Hubner), relies on multimodal sensory information to find food, mates, mating and ovipositional grounds. Successful phytosanitary monitoring demands for the bait for the field traps to obtain the most reliable representation of pest abundance. Attraction to light and blend of key components of host plant odor, was tested both in the laboratory and field conditions. Ultraviolet light, which was the most effective in the wind tunnel experiments, was further tested in the field alone and in combination with bisexual lure. Bisexual lure, being attractive in the lab, as well as in the field, did not improve responses to ultraviolet in both experimental designs. All three baits attracted significantly more females than males in the field. Wind tunnel experiments revealed that ultraviolet elicited the shortest response latencies either alone or paired with the odor bait. The lack of synergistic effect between attractive light and odor stimuli is an important issue for pest monitoring. The possible reasons for the observed lack of synergy are the hierarchy of behavioral responses to different stimuli or the intensities of both stimuli are critically important for attractivity of combined stimulus and differ from separately presented ones.

Transgenic line for characterizing GABA-receptor expression to study the neural basis of olfaction in the yellow-fever mosquito.

The mosquito Aedes aegypti is an important vector of diseases including dengue, Zika, chikungunya, and yellow fever. Olfaction is a critical modality for mosquitoes enabling them to locate hosts, sources of nectar, and sites for oviposition. GABA is an essential neurotransmitter in olfactory processing in the insect brain, including the primary olfactory center, the antennal lobe. Previous work with Ae. aegypti has suggested that antennal lobe inhibition via GABA may be involved in the processing of odors. However, little is known about GABA receptor expression in the mosquito brain, or how they may be involved in odor attraction. In this context, generating mutants that target the mosquito's olfactory responses, and particularly the GABAergic system, is essential to achieve a better understanding of these diverse processes and olfactory coding in these disease vectors. Here we demonstrate the potential of a transgenic line using the QF2 transcription factor, GABA-B1QF2-ECFP, as a new neurogenetic tool to investigate the neural basis of olfaction in Ae. aegypti. Our results show that the gene insertion has a moderate impact on mosquito fitness. Moreover, the line presented here was crossed with a QUAS reporter line expressing the green fluorescent protein and used to determine the location of the metabotropic GABA-B1 receptor expression. We find high receptor expression in the antennal lobes, especially the cell bodies surrounding the antennal lobes. In the mushroom bodies, receptor expression was high in the Kenyon cells, but had low expression in the mushroom body lobes. Behavioral experiments testing the fruit odor attractants showed that the mutants lost their behavioral attraction. Together, these results show that the GABA-B1QF2-ECFP line provides a new tool to characterize GABAergic systems in the mosquito nervous system.

Dietary E. coli promotes age-dependent chemotaxis decline in C. elegans

An animal’s ability to sense odors declines during aging, and its olfactory drive is tuned by internal states such as satiety. However, whether internal states modulate an age-dependent decline in odor sensation is unknown. To address this issue, we utilized the nematode Caenorhabditis elegans and compared their chemotaxis abilities toward attractive odorants when aged under different dietary conditions. Feeding with the standard laboratory diet, Escherichia coli attenuated the chemotaxis ability toward diacetyl, isoamyl alcohol, and benzaldehyde when aged. On the other hand, feeding with either the lactic acid bacteria Lactobacillus reuteri or food deprivation selectively maintained the chemotaxis ability toward diacetyl. Our results suggest that ingestion of E. coli causes age-dependent chemotaxis decline. The changes in the chemotaxis behavior are attributed to the different expressions of diacetyl receptor odr-10, and the chemotaxis behavior of aged animals under food deprivation is shown to be dependent on daf-16. Our study demonstrates the molecular mechanism of how diet shapes the trajectory of age-dependent decline in chemosensory behaviors.

Age-related differences in perception and coding of attractive odorants in mice

Hedonic perception deeply changes with aging, significantly impacting health and quality of life in elderly. In young adult mice, an odor hedonic signature is represented along the antero-posterior axis of olfactory bulb, and transferred to the olfactory tubercle and ventral tegmental area, promoting approach behavior. Here, we show that while the perception of unattractive odorants was unchanged in older mice (22 months), the appreciation of some but not all attractive odorants declined. Neural activity in the olfactory bulb and tubercle of older mice was consistently altered when attraction to pleasant odorants was impaired while maintained when the odorants kept their attractivity. Finally, in a self-stimulation paradigm, optogenetic stimulation of the olfactory bulb remained rewarding in older mice even without ventral tegmental area’s response to the stimulation. Aging degrades behavioral and neural responses to some pleasant odorants but rewarding properties of olfactory bulb stimulation persisted, providing new insights into developing novel olfactory training strategies to elicit motivation even when the dopaminergic system is altered as observed in normal and/or neurodegenerative aging.

Descending control and regulation of spontaneous flight turns in Drosophila

The clumped distribution of resources in the world has influenced the pattern of foraging behavior since the origins of locomotion, selecting for a common search motif in which straight movements through resource-poor regions alternate with zig-zag exploration in resource-rich domains. For example, during local search, flying flies spontaneously execute rapid flight turns, called body saccades, but suppress these maneuvers during long-distance dispersal or when surging upstream toward an attractive odor. Here, we describe the key cellular components of a neural network in flies that generate spontaneous turns as well as a specialized pair of neurons that inhibits the network and suppresses turning. Using 2-photon imaging, optogenetic activation, and genetic ablation, we show that only four descending neurons appear sufficient to generate the descending commands to execute flight saccades. The network is organized into two functional units-one for right turns and one for left-with each unit consisting of an excitatory (DNae014) and an inhibitory (DNb01) neuron that project to the flight motor neuropil within the ventral nerve cord. Using resources from recently published connectomes of the fly, we identified a pair of large, distinct interneurons (VES041) that form inhibitory connections to all four saccade command neurons and created specific genetic driver lines for this cell. As predicted by its connectivity, activation of VES041 strongly suppresses saccades, suggesting that it promotes straight flight to regulate the transition between local search and long-distance dispersal. These results thus identify the key elements of a network that may play a crucial role in foraging ecology.

The conserved RNA-binding protein Imp is required for the specification and function of olfactory navigation circuitry in Drosophila

Complex behaviors depend on the precise developmental specification of neuronal circuits, but the relationship between genetic programs for neural development, circuit structure, and behavioral output is often unclear. The central complex (CX) is a conserved sensory-motor integration center in insects, which governs many higher-order behaviors and largely derives from a small number of type II neural stem cells (NSCs). Here, we show that Imp, a conserved IGF-II mRNA-binding protein expressed in type II NSCs, plays a role in specifying essential components of CX olfactory navigation circuitry. We show the following: (1) that multiple components of olfactory navigation circuitry arise from type II NSCs. (2) Manipulating Imp expression in type II NSCs alters the number and morphology of many of these circuit elements, with the most potent effects on neurons targeting the ventral layers of the fan-shaped body (FB). (3) Imp regulates the specification of Tachykinin-expressing ventral FB input neurons. (4) Imp is required in type II NSCs for establishing proper morphology of the CX neuropil structures. (5) Loss of Imp in type II NSCs abolishes upwind orientation to attractive odor while leaving locomotion and odor-evoked regulation of movement intact. Taken together, our findings establish that a temporally expressed gene can regulate the expression of a complex behavior by developmentally regulating the specification of multiple circuit components and provides a first step toward a developmental dissection of the CX and its roles in behavior.

Precise sensorimotor control impacts reproductive fitness of C. elegans in 3D environments.

The ability of animals to sense and navigate towards relevant cues in complex and elaborate habitats is paramount for their survival and reproductive success. The nematode Caenorhabditis elegans uses a simple and elegant sensorimotor program to track odors in its environments. Whether this allows the worm to effectively navigate a complex environment and increase its evolutionary success has not been tested yet. We designed an assay to test whether C. elegans can track odors in a complex 3D environment. We then used a previously established 3D cultivation system to test whether defect in tracking odors to find food in a complex environment affected their brood size. We found that wild-type worms can accurately migrate toward a variety of odors in 3D. However, mutants of the muscarinic acetylcholine receptor GAR-3 which have a sensorimotor integration defect that results in a subtle navigational defect steering towards attractive odors, display decreased chemotaxis to the odor butanone not seen in the traditional 2D assay. We also show that the decreased ability to locate appetitive stimuli in 3D leads to reduced brood size not observed in the standard 2D culture conditions. Our study shows that mutations in genes previously overlooked in 2D conditions can have a significant impact in the natural habitat, and highlights the importance of considering the evolutionary selective pressures that have shaped the behavior, as well as the underlying genes and neural circuits.

The health perception of urban green spaces and its emotional impact on young adults: an empirical study from three cities in China.

Exposure to green space can bring many benefits to physical and mental health, but in China, the attractiveness of green space to youth groups seems to be not significant. The question of how to encourage young people to go out of the house to better perceive green space, enjoy nature, and promote physical and mental health is on our minds. This study combines young people's green space perception, green space use, and purpose of visit to explore its impact on the emotional health of youth groups, combined with the PANAS psychological data scale, an online questionnaire survey of 426 residents (18-35 years old) in three Chinese cities, and was used to construct a multiple regression model and AMOS structural equations. The results of the study showed that, firstly, environmental attractiveness, environmental odor, and number of facilities were the key factors influencing adolescents' landscape perception evaluation, while activity space, environmental odor, and environmental attractiveness had a greater impact on adolescents' emotional well-being. Second, among adolescents' visit purposes, socializing and fitness were more likely to help them generate positive emotions while resting and viewing activities were effective in helping them alleviate negative emotions. In addition, in terms of usage, residents who took public transportation as well as those who arrived on foot were the most emotionally healthy. The findings of this paper provide insights for public policymakers, urban planners, and landscape architects to better encourage youth participation in green spaces when they are installed.

Active smelling in the American cockroach.

Motion plays an essential role in sensory acquisition. From changing the position in which information can be acquired to fine scale probing and active sensing, animals actively control the way they interact with the environment. In olfaction, movement impacts the time and location of odour sampling as well as the flow of odour molecules around the olfactory organs. Employing a detailed spatiotemporal analysis, we investigate how the insect antennae interact with the olfactory environment in a species with a well studied olfactory system - the American cockroach. Cockroaches were tested in a wind-tunnel setup during the presentation of odours with different attractivity levels: colony extract, butanol and linalool. Our analysis revealed significant changes in antennal kinematics when odours are presented, including a shift towards the stream position, an increase in vertical movement and high-frequency local oscillations. Nevertheless, the antennal shifting occurred predominantly in a single antenna while the overall range covered by both antennae was maintained throughout. These findings hold true for both static and moving stimuli and are more pronounced for attractive odours. Furthermore, we find that upon odour encounter, there is an increased occurrence of high-frequency antennal sweeps and vertical strokes, which are shown to impact the olfactory environment's statistics directly. Our study lays out a tractable system for exploring the tight coupling between sensing and movement, in which antennal sweeps, in parallel to mammalian sniffing, are actively involved in facilitating odour capture and transport, generating odour intermittency in environments with low air movement where cockroaches dwell.

Immunoactivation Affects Perceived Body Odor and Facial but Not Vocal Attractiveness.

Several previous studies have shown that in mammals, the health status of conspecifics can be assessed based on perceptual cues. Olfactory, visual, or acoustic cues may lead to avoidant behavior, thus reducing the risk of contagion by close contact with infected individuals. We tested whether immune system activation after immunization leads to perceptible changes in body odor and facial and vocal attractiveness in humans. We have experimentally activated the immune system of male participants using vaccination against hepatitis A/B and meningococcus. Their body odor, facial photographs, and vocal recordings were collected before and 14 days after vaccination. Subsequently, the body odor samples, facial photographs, and vocal recordings were assessed by female raters for their attractiveness and healthiness. We have also measured skin coloration (from facial photographs and in vivo using a spectrophotometer), vocal parameters, and C-reactive protein (CRP) levels as a marker of inflammation. We found an increase in perceived body odor attractiveness, a decrease in facial attractiveness and healthiness, and no change in vocal attractiveness 14 days after vaccination compared to the prevaccination condition. Moreover, there was no change in facial coloration or vocal parameters between the prevaccination and postvaccination conditions. Prevaccination CRP levels were negatively associated with body odor and facial attractiveness and positively associated with body odor intensity. Overall, our results suggest that perceived body odor as well as facial but not vocal attractiveness may provide cues to activation of the immune response and that each modality may carry specific information about the individual's condition.

Prevalence of Bovine Trypanosomosis and Density of Tsetse Fly in Duguna Fango District, Wolaita Zone, Southern Ethiopia

A cross-sectional study was conducted from December 2017 to April 2018 in Diguna Fango district in Wolaita zone, Southern Ethiopia, with the objectives to determine the prevalence of bovine trypanosomosis and to assess the distribution and apparent densities of vectors of the trypanosomosis. A parasitological study using buffy coat technique was employed for the determination of prevalence of trypanosomosis while monoconical traps were used for the vector studies. A total of 192 cattle randomly selected from the study population were examined for the parasitological study. The result of parasitological study revealed that the overall prevalence of trypanosomosis was found to be 7.3% in Duguna Fango district. The prevalence showed no significant difference in susceptibility between sex categories and in age groups (P>0.05). From the infected animals the prevalence for trypanosome species was 14.3% and 85.7% for T. vivax and T. congolense, respectively. The mean PCV values of parasitaemic and aparasitaemic animals were 19.7% and 25.7, respectively. About 20 monoconical traps in two kebele (Bilate and Anka) of Duguna Fango districts were deployed for 72 hours with odour attractants for the vector studies. There were 22 G. pallidipes and 43 tabanus had been collected from the study site with the respective density of 1.1 and 2.15 fly/trap/day. Therefore, implementing control of trypanosomosis with an integrated approach was paramount importance in areas of the study site.

Carbonyl products of ozone oxidation of volatile organic compounds can modulate olfactory choice behavior in insects

Insects are a diverse group of organisms that provide important ecosystem services like pollination, pest control, and decomposition and rely on olfaction to perform these services. In the Anthropocene, increasing concentrations of oxidant pollutants such as ozone have been shown to corrupt odor-driven behavior in insects by chemically degrading e.g. flower signals or insect pheromones. The degradation, however, does not only result in a loss of signals, but also in a potential enrichment of oxidation products, predominantly small carbonyls. Whether and how these oxidation products affect insect olfactory perception remains unclear. We examined the effects of ozone-generated small carbonyls on the olfactory behavior of the vinegar fly Drosophila melanogaster. We compiled a broad collection of neurophysiologically relevant odorants for the fly from databases and literature and predicted the formation of the types of stable small carbonyl products resulting from the odorant's oxidation by ozone. Based on these predictions, we evaluated the olfactory detection and behavioral impact of the ten most frequently predicted carbonyl products in the fly using single sensillum recordings (SSRs) and behavioral tests. Our results demonstrate that the fly's olfactory system can detect the oxidation products, which then elicit either attractive or neutral behavioral responses, rather than repulsion. However, certain products alter behavioral choices to an attractive odor source of balsamic vinegar. Our findings suggest that the enrichment of small carbonyl oxidation products due to increased ozone levels can affect olfactory guided insect behavior. Our study underscores the implications for odor-guided foraging in insects and the essential ecosystem services they offer under carbonyl enriched environments.

Effect of various odour attractants on egg-laying activity of black soldier flies (Hermetia illucens)

Abstract The black soldier fly, Hermetia illucens (Diptera: Stratiomyidae), is a cosmopolitan fly. Its feeding behaviour, high productivity and the high value of its larvae in macronutrients (mainly lipids and proteins) makes this species one of the promising candidates for large scale insect farming and organic waste management. The reproductive rate, female oviposition preference and oviposition attractants of H. illucens are understudied. A better knowledge of the attractants involved in oviposition site choice would help maximising black soldier fly reproductive success. The current study aims to compare the efficacy of four food attractants on the oviposition activity of H. illucens females. The trial was conducted in a cage (11 × 1.25 × 0.9 m) with a volume of 12.38 m3 and containing 83,610 adults (6750 adults/m3). The cages were placed in a rearing room where the conditions were: T = 28 ± 1 °C, RH = 70 ± 5%, photoperiod of 16 h light: 8 h dark and light intensity = 8140 Lux). The tested feeds included a rabbit feed, fish waste (sardine, sardinella, and anchovy waste), a mixture of tropical fruits (pineapple, banana, papaya and mango), and fresh cattle manure. The performance of each feed attractant was evaluated in terms of the mass of eggs laid on the laying medium. This study showed that fruit mixture is the most efficient attractant, followed by fresh cattle manure and fish waste while the rabbit feed was the least efficient. The results of this study can be used to optimise the reproduction of the black soldier fly.

Pig olfaction: the potential impact and use of odors in commercial pig husbandry

Pigs are widely acknowledged for their olfactory abilities. Research on pigs’ olfactory capacities has focused mainly on aspects of olfaction that directly impact production, such as palatability of feed and pheromones to stimulate reproduction. Several basic research questions remain unanswered, such as which odors do pigs like/dislike, and how may odors enrich their lives? This review aims to explore the currently available literature on pig olfaction to elucidate the current knowns and unknowns within the following topics: chemicals in a pig’s environment, the olfactory organs of pigs, olfactory detection and acuity, behavioral reactions to odors, aversive odors, reaction to novel odors, attractive odors, and odors as a management tool in commercial pig production. The review focuses on complex odors of non-social origin (e.g., ammonia), and when information on this topic is lacking we include information from research on other mammalian species. We found that the olfactory organs of pigs are already functional at birth and that piglets can recognize the smell of the sow within 12h postpartum. Compared with humans and several other mammalian species, the pig’s olfactory system is highly developed, and the use of their sense of smell is incorporated into their natural behavior. While sniffing is a well-known behavior in pigs’ exploratory behavioral repertoire, this review points to a lack of knowledge on pigs’ behavioral reactions specifically when exposed to odors. Some odors appear attractive to pigs, whereas others appear repellent. Depending on the properties of the odor, providing pigs access to odors may be a way to stimulate their sense of smell, and could possibly be used in commercial pig production to enrich their lives. The review lastly highlights potential risks for animal welfare caused from lacking knowledge about how pigs perceive odors in their environment, and proposes future research questions and ways to utilize pigs’ sense of smell in the daily management of these animals. Further research on the olfactory abilities of pigs could help to ensure a more sustainable pig production.

Inheritance of associative memories and acquired cellular changes in C. elegans

Experiences have been shown to modulate behavior and physiology of future generations in some contexts, but there is limited evidence for inheritance of associative memory in different species. Here, we trained C. elegans nematodes to associate an attractive odorant with stressful starvation conditions and revealed that this associative memory was transmitted to the F1 progeny who showed odor-evoked avoidance behavior. Moreover, the F1 and the F2 descendants of trained animals exhibited odor-evoked cellular stress responses, manifested by the translocation of DAF-16/FOXO to cells’ nuclei. Sperm, but not oocytes, transmitted these odor-evoked cellular stress responses which involved H3K9 and H3K36 methylations, the small RNA pathway machinery, and intact neuropeptide secretion. Activation of a single chemosensory neuron sufficed to induce a serotonin-mediated systemic stress response in both the parental trained generation and in its progeny. Moreover, inheritance of the cellular stress responses increased survival chances of the progeny as exposure to the training odorant allowed the animals to prepare in advance for an impending adversity. These findings suggest that in C. elegans associative memories and cellular changes may be transferred across generations.