Scent Discrimination Research Articles

Population Scent Discrimination in Two Liolaemus Lizard Species: Exploring Ethological Isolation

Reproductive isolating barriers are a crucial element in the speciation process. From these barriers, and among those acting early in the speciation process (premating), the ethological ones can play a pivotal role in isolating populations or closely related species. In fact, the high diversity of some taxa has been correlated with an elevated divergence in sexual signals, which facilitates isolation. The present study explored whether variation in chemical signals may contribute to the high diversity of Liolaemus lizards, a genus with more than 290 species. Specifically, population scent discrimination was investigated in two sympatric species, L. tenuis and L. lemniscatus, studying the response of closely located populations most likely from the same genetic lineages. Lizards of both species discriminated between scents of their own and different populations, and in some cases, scents from their own population were preferred. These results suggest a fast evolution of scents and/or of their discrimination, implying that the ethological barriers involving the chemical modality may evolve fast. The studied species, however, differed in the strength of the exhibited population scent discrimination, suggesting that the ethological barriers may evolve at different rates across species. It can be concluded that ethological barriers involving chemical modality may disrupt species’ cohesion, potentially contributing to Liolaemus diversification, in synergy or not with geographical barriers.

Field-realistic acute exposure to glyphosate-based herbicide impairs fine-color discrimination in bumblebees.

Pollinator decline is a grave challenge worldwide. One of the main culprits for this decline is the widespread use of, and pollinators' chronic exposure to, agrochemicals. Here, we examined the effect of a field-realistic dose of the world's most commonly used pesticide, glyphosate-based herbicide (GBH), on bumblebee cognition. We experimentally tested bumblebee (Bombus terrestris) color and scent discrimination using acute GBH exposure, approximating a field-realistic dose from a day's foraging in a patch recently sprayed with GBH. In a 10-color discrimination experiment with five learning bouts, GBH treated bumblebees' learning rate fell to zero by third learning bout, whereas the control bees increased their performance in the last two bouts. In the memory test, the GBH treated bumblebees performed to near chance level, indicating that they had lost everything they had learned during the learning bouts, while the control bees were performing close to the level in their last learning bout. However, GBH did not affect bees' learning in a 2-color or 10-odor discrimination experiment, which suggests that the impact is limited to fine color learning and does not necessarily generalize to less specific tasks or other modalities. These results indicate that the widely used pesticide damages bumblebees' fine-color discrimination, which is essential to the pollinator's individual success and to colony fitness in complex foraging environments. Hence, our study suggests that acute sublethal exposure to GBH poses a greater threat to pollination-based ecosystem services than previously thought, and that tests for learning and memory should be integrated into pesticide risk assessment.

Preliminary tests show bisphenol-A reduces memory and scent discrimination in tests of rat olfactory performance

Over 10% of the 260 million tons of plastic produced each year ends up in Earth's oceans. Despite worldwide efforts to limit plastic waste, many organisms have already been exposed to plastic waste for prolonged periods. Plastic degradation releases biologically active compounds (e.g. bisphenol-A (BPA)). Studies have demonstrated that BPA can affect brain development and function, but little is known about its impact on physiological activity or brain function. The aim of this research is to assess the effect of BPA on olfaction in order to understand how BPA might affect marine organisms that are critically dependent on olfaction for survival. Operant conditioning was used to train two groups of laboratory rats (Rattus norvegicus) to detect the scent of lemon juice. Rats in the experimental group received water containing 0.05 mg/kg/day of BPA for five weeks, and then 0.10 mg/kg of BPA for nine weeks. Performance variables measured included sensitivity, scent discrimination, and memory. Data analysis with a general linear mixed model found a small significant difference (based on p-value) in performance between the two groups of rats before BPA administration, and a stronger difference in scent discrimination afterward. After BPA administration, repeated measures tests found significant differences within the experimental group in the rats' ability to remember the target scent. These preliminary results suggest a need for expanded testing. If these results are then confirmed, we recommend additional research examining the effects of plastic waste on the olfactory capabilities and survival of terrestrial and marine species in their native habitats.

Sniff Species: SURMOF-Based Sensor Array Discriminates Aromatic Plants beyond the Genus Level

Lamiaceae belong to the species-richest family of flowering plants and harbor many species that are used as herbs or in medicinal applications such as basils or mints. The evolution of this group has been driven by chemical speciation, mainly volatile organic compounds (VOCs). The commercial use of these plants is characterized by adulteration and surrogation to a large extent. Authenticating and discerning this species is thus relevant for consumer safety but usually requires cumbersome analytics, such as gas chromatography, often coupled with mass spectroscopy. Here, we demonstrate that quartz-crystal microbalance (QCM)-based electronic noses provide a very cost-efficient alternative, allowing for fast, automated discrimination of scents emitted from the leaves of different plants. To explore the range of this strategy, we used leaf material from four genera of Lamiaceae along with lemongrass, which is similarly scented but from an unrelated outgroup. To differentiate the scents from different plants unambiguously, the output of the six different SURMOF/QCM sensors was analyzed using machine learning (ML) methods together with a thorough statistical analysis. The exposure and purging of data sets (four cycles) obtained from a QCM-based, low-cost homemade portable e-Nose were analyzed using a linear discriminant analysis (LDA) classification model. Prediction accuracy with repeated test measurements reached values of up to 0%. We show that it is possible not only to discern and identify plants at the genus level but also to discriminate closely related sister clades within a genus (basil), demonstrating that an e-Nose is a powerful device that can safeguard consumer safety against dangers posed by globalized trade.

Cognitive Abilities of Dogs with Mucopolysaccharidosis I: Learning and Memory

Simple SummaryLysosomes are cell organelles that contain enzymes that break down large molecules to be recycled or discarded. When lysosomal enzymes fail to perform this function, molecules become trapped and cause cellular destruction. Mucopolysaccharidosis I (MPS I) is a rare disease that occurs in dogs and humans due to a deficiency of the lysosomal enzyme, alpha-L-iduronidase. Humans affected with MPS I experience mild to severe clinical signs in facial features, skeletal changes, cognitive decline, and heart, liver, and respiratory disease. Similarly, MPS I in dogs also cause facial changes, musculoskeletal degeneration, spinal cord compression, and heart and liver disease. However, the cognitive ability in dogs affected with MPS I has not been investigated. The purpose of this pilot study was to determine the feasibility of conducting cognitive tests on MPS I affected dogs and their cognitive abilities. Three groups of dogs were tested: MPS I untreated, MPS I treated, and clinically normal. Dogs were successfully trained to perform the cognitive tests. Differences in their ability to reach the criterion was evident in attention oddity and scent discrimination tests. This study found cognition testing of dogs affected with MPS I to be feasible and recommend future studies focus on a single cognitive domain at a time.Mucopolysaccharidosis I (MPS I) results from a deficiency of a lysosomal enzyme, alpha-L-iduronidase (IDUA). IDUA deficiency leads to glycosaminoglycan (GAG) accumulation resulting in cellular degeneration and multi-organ dysfunction. The primary aims of this pilot study were to determine the feasibility of cognitive testing MPS I affected dogs and to determine their non-social cognitive abilities with and without gene therapy. Fourteen dogs were tested: 5 MPS I untreated, 5 MPS I treated, and 4 clinically normal. The treated group received intrathecal gene therapy as neonates to replace the IDUA gene. Cognitive tests included delayed non-match to position (DNMP), two-object visual discrimination (VD), reversal learning (RL), attention oddity (AO), and two-scent discrimination (SD). Responses were recorded as correct, incorrect, or no response, and analyzed using mixed effect logistic regression analysis. Significant differences were not observed among the three groups for DNMP, VD, RL, or AO. The MPS I untreated dogs were excluded from AO testing due to failing to pass acquisition of the task, potentially representing a learning or executive function deficit. The MPS I affected group (treated and untreated) was significantly more likely to discriminate between scents than the normal group, which may be due to an age effect. The normal group was comprised of the oldest dogs, and a mixed effect logistic model indicated that older dogs were more likely to respond incorrectly on scent discrimination. Overall, this study found that cognition testing of MPS I affected dogs to be feasible. This work provides a framework to refine future cognition studies of dogs affected with diseases, including MPS I, in order to assess therapies in a more comprehensive manner.

Genetic variation at MHC class II loci influences both olfactory signals and scent discrimination in ring-tailed lemurs

BackgroundDiversity at the Major Histocompatibility Complex (MHC) is critical to health and fitness, such that MHC genotype may predict an individual’s quality or compatibility as a competitor, ally, or mate. Moreover, because MHC products can influence the components of bodily secretions, an individual’s body odors may signal its MHC composition and influence partner identification or mate choice. Here, we investigated MHC-based signaling and recipient sensitivity by testing for odor-gene covariance and behavioral discrimination of MHC diversity and pairwise dissimilarity in a strepsirrhine primate, the ring-tailed lemur (Lemur catta).MethodsFirst, we coupled genotyping of the MHC class II gene, DRB, with gas chromatography-mass spectrometry of genital gland secretions to investigate if functional genetic diversity is signaled by the chemical diversity of lemur scent secretions. We also assessed if the chemical similarity between individuals correlated with their MHC-DRB similarity. Next, we assessed if lemurs discriminated this chemically encoded, genetic information in opposite-sex conspecifics.ResultsWe found that both sexes signaled overall MHC-DRB diversity and pairwise MHC-DRB similarity via genital secretions, but in a sex- and season-dependent manner. Additionally, the sexes discriminated absolute and relative MHC-DRB diversity in the genital odors of opposite-sex conspecifics, suggesting that lemur genital odors function to advertise genetic quality.ConclusionsIn summary, genital odors of ring-tailed lemurs provide honest information about an individual’s absolute and relative MHC quality. Complementing evidence in humans and Old World monkeys, we suggest that reliance on scent signals to communicate MHC quality may be important across the primate lineage.

Rapid acquisition of antipredatory responses to new predators by an insular lizard

Alien predators may impose a great threat to naive prey. Ibiza wall lizards (Podarcis pityusensis) live in Ibiza, a snake-free island until 2003. We studied the lizards’ discrimination of scents of two invader snakes: one that depredates lizards, the horseshoe whip snake (Hemorrhois hippocrepis), and another that does not, the ladder snake (Rhinechis scalaris). We compared two populations of Ibiza wall lizards: one from the main island of Ibiza, which coexists with both snakes, and another from the nearby snake-free islet of Sal Rossa. Lizards from Ibiza recognized the scent of the horseshoe whip snake and responded with clear antipredatory behaviours. However, they reacted to the scent of the ladder snake similarly to that of the controls (odourless control and pungent scent). Lizards from Sal Rossa did not respond to any of the snakes or the controls. Our results show that lizards can rapidly acquire the ability to react to a novel predator. As only about ten generations of lizards have coexisted with snakes, the most plausible explanation to our results is that lizards have learned to associate the scent of the predatory snake with a threat. This is the first study reporting the rapid acquisition of lizards’ antipredatory responses to the chemical cues of novel predators. However, more research is needed in order to identify the mechanisms implicated in the response. How naive prey acquire antipredator behaviour is both important for basic scientific research and useful for the conservation of native species subjected to biological invasions. The island of Ibiza (Spain) has been free from snakes until their introduction by humans in 2003. We compared the reaction of lizards from Ibiza (where presently three species of snakes cohabitate) and lizards from Sal Rossa (a nearby snake-free islet) to the scent of two snakes (one that feeds on lizards and other that does not). The results were clear: lizards from Ibiza react to the scent of the predatory snake with antipredatory behaviours, while ignoring the scent of the non-predatory snake. Lizards from the snake-free island of Sal Rossa did not react to any of the snakes. Our study shows that lizards can rapidly acquire the ability to react to a completely new type of predator, most likely by learning.

Chemical recognition of conspecifics in a neotropical lizard, Liolaemus pacha (Iguania: Liolaemidae): relation to visual displays, season and sex

Chemical cues play an important role in sexual recognition in several lizard species. Here, we investigated whether the neotropical lizard, Liolaemus pacha (Iguania: Liolaemidae) can discriminate between chemical information obtained from males or females. In addition, we also considered the effect of season (reproductive vs. post-reproductive) and the sex of the tested individual. We experimentally tested scent discrimination, using a terrarium previously occupied by a male, a female, and an untreated terrarium as control as sources of different chemical scents. We counted the number of tongue flicks, a measure of chemical exploratory behavior, and the visual displays triggered by these scents for 10 min. Males performed significantly more tongue flicks when female scent was present than when male and control scents were present, indicating sexual recognition. However, females did not show a significant difference in those same conditions, indicating a lack of sexual recognition. For visual displays, males showed significantly higher rates to female and male scents than to control, whereas females did not show any difference. During the reproductive season, the number of tongue flicks and visual displays were higher than during the post-reproductive season. Our results suggest that for male L. pacha, chemical cues play an important role in mate recognition. We discuss the apparent lack of recognition in females. We suggest that the observed seasonal behavioral differences might be associated with physiological changes related mainly to reproduction.

Chemoreception and mating behaviour of a tropical Australian skink

In many reptile groups, molecular systematics is currently revealing high levels of cryptic diversity (i.e. genetically distinct lineages that are difficult to distinguish morphologically). One obvious mode for mate discrimination in these cryptic species is chemoreception. We hypothesise that diversity in these groups is not cryptic for pheromones, and mate recognition via chemoreception may be the primary reproductive isolating mechanism. Here, we present a preliminary study of chemoreception in Lampropholis coggeri, a rainforest skink of north-eastern Australia. We first describe the mating behaviour of captive pairs, showing that tongue-flicking is an important component for both males and females, and find that L. coggeri mate more readily when paired with a conspecific from their own population vs. from a nearby population. Based on the assumption that tongue-flicking represents the lizard’s interest, we then experimentally tested scent discrimination using lizard-swabbed cotton buds presented to captive individuals. We found both sexes tongue-flicked more to conspecific scent than to unscented controls. Males tongue-flicked more to female scent than to male scent but did not discriminate between mated and unmated females. While females showed greater interest in conspecific scent, they showed no greater interest in scent from males than females. This lack of discrimination was true for both mated and unmated females. Unexpectedly, however, mated females tongue-flicked substantially more than unmated females. Finally, males tended to tongue flick more often to female scents from their own population than to a nearby population that is moderately genetically divergent. Our results suggest that chemoreception plays a role in mate recognition in this species. Further work should extend to establishing mate recognition between the highly divergent cryptic lineages within this species and the pheromones underlying mate recognition.

The Dig Task: A Simple Scent Discrimination Reveals Deficits Following Frontal Brain Damage

Cognitive impairment is the most frequent cause of disability in humans following brain damage, yet the behavioral tasks used to assess cognition in rodent models of brain injury is lacking. Borrowing from the operant literature our laboratory utilized a basic scent discrimination paradigm1-4 in order to assess deficits in frontally-injured rats. Previously we have briefly described the Dig task and demonstrated that rats with frontal brain damage show severe deficits across multiple tests within the task5. Here we present a more detailed protocol for this task. Rats are placed into a chamber and allowed to discriminate between two scented sands, one of which contains a reinforcer. The trial ends after the rat either correctly discriminates (defined as digging in the correct scented sand), incorrectly discriminates, or 30 sec elapses. Rats that correctly discriminate are allowed to recover and consume the reinforcer. Rats that discriminate incorrectly are immediately removed from the chamber. This can continue through a variety of reversals and novel scents. The primary analysis is the accuracy for each scent pairing (cumulative proportion correct for each scent). The general findings from the Dig task suggest that it is a simple experimental preparation that can assess deficits in rats with bilateral frontal cortical damage compared to rats with unilateral parietal damage. The Dig task can also be easily incorporated into an existing cognitive test battery. The use of more tasks such as this one can lead to more accurate testing of frontal function following injury, which may lead to therapeutic options for treatment. All animal use was conducted in accordance with protocols approved by the Institutional Animal Care and Use Committee.

The Dig Task: A Simple Scent Discrimination Reveals Deficits Following Frontal Brain Damage

Cognitive impairment is the most frequent cause of disability in humans following brain damage, yet the behavioral tasks used to assess cognition in rodent models of brain injury is lacking. Borrowing from the operant literature our laboratory utilized a basic scent discrimination paradigm1-4in order to assess deficits in frontally-injured rats. Previously we have briefly described the Dig task and demonstrated that rats with frontal brain damage show severe deficits across multiple tests within the task5. Here we present a more detailed protocol for this task. Rats are placed into a chamber and allowed to discriminate between two scented sands, one of which contains a reinforcer. The trial ends after the rat either correctly discriminates (defined as digging in the correct scented sand), incorrectly discriminates, or 30 sec elapses. Rats that correctly discriminate are allowed to recover and consume the reinforcer. Rats that discriminate incorrectly are immediately removed from the chamber. This can continue through a variety of reversals and novel scents. The primary analysis is the accuracy for each scent pairing (cumulative proportion correct for each scent). The general findings from the Dig task suggest that it is a simple experimental preparation that can assess deficits in rats with bilateral frontal cortical damage compared to rats with unilateral parietal damage. The Dig task can also be easily incorporated into an existing cognitive test battery. The use of more tasks such as this one can lead to more accurate testing of frontal function following injury, which may lead to therapeutic options for treatment. All animal use was conducted in accordance with protocols approved by the Institutional Animal Care and Use Committee.

A Discrimination Task Used as a Novel Method of Testing Decision-Making Behavior following Traumatic Brain Injury

Traumatic brain injury (TBI) results in a multitude of deficits following injury. Some of the most pervasive in humans are the changes that affect frontally-mediated cognitive functioning, such as decision making. The assessment of decision-making behavior in rodents has been extensively tested in the field of the experimental analysis of behavior. However, due to the narrow therapeutic window following TBI, time-intensive operant paradigms are rarely incorporated into the battery of tests traditionally used, the majority of which assess motor and sensory functioning. The cognitive measures that are used are frequently limited to memory and do not account for changes in decision-making behavior. The purpose of the present study was to develop a simplified discrimination task that can assess deficits in decision-making behavior in rodents. For the task, rats were required to dig in cocoa-scented sand (versus unscented sand) for a reinforcer. Rats were given 12 sessions per day until a criterion level of 80% accuracy for 3 days straight was reached. Once the criterion was achieved, cortical contusion injuries were induced (frontal, parietal, or sham). Following a recovery period, the rats were re-tested on cocoa versus unscented sand. Upon reaching criterion, a reversal discrimination was evaluated in which the reinforcer was placed in unscented sand. Finally, a novel scent discrimination (basil versus coffee with basil reinforced), and a reversal (coffee) were evaluated. The results indicated that the Dig task is a simple experimental preparation that can be used to assess deficits in decision-making behavior following TBI.

Trained Dogs Outperform Human Surveyors in the Detection of Rare Spotted Knapweed (Centaurea stoebe)

AbstractInvasive plants have devastating effects on ecosystems and biodiversity that early intervention can prevent. Eradication or containment of new invasions is difficult to achieve because of constraints posed by the low density and detectability of individuals. Domestic dogs trained to cue on distinctive scents might provide an effective method to detect spotted knapweed. The objective of this study was to compare the accuracy and detection distances of dogs to humans in locating new spotted knapweed (Centaurea stoebe) invasions. Three dogs, trained to detect knapweed using scent discrimination and tracking techniques, were compared with human surveyors. Seven sampling units (0.5 ha [1.2 ac]) were delineated in a grazed dryland pasture. Dogs, with their handlers, and human surveyors performed line-transect surveys in fall 2005 and spring, summer, and fall 2006. Dog accuracy for large-size knapweed targets (infestations 0.52 m3[18.4 ft3]) was similar to human accuracy and better than humans (94 vs. 78%) for medium-size targets (infestations 0.13m3). Dog accuracy (67%) was greater (> 81% probability) than humans (34%) for small targets (plants; 0.02 m3). Overall dog accuracy (81%) andF-measure scores (86%) were better than human scores, 59% and 74%, respectively. Human precision was greater (100%) than dogs at 94%. Dogs detected a larger percentage of small targets (80%) at distances greater than 7.9 m (26 ft) compared with humans at only 20%. Our results indicate dogs are more accurate than humans are, especially at critical detection of small spotted knapweed plants, and from greater distances. Invasive plant monitoring using detection dogs can provide greater overall accuracy of plant detection.

Comparison between Human Scent Compounds Collected on Cotton and Cotton Blend Materials for SPME-GC/MS Analysis

Human scent evidence has been used for centuries in various European countries and is now becoming more prevalent in the United States. Human scent evidence is collected either directly or indirectly and then used for scent discrimination with specially trained canines. The direct method allows the canine to smell an article of evidence, whereas the indirect method involves pre-scenting the canine with a sorbent material onto which traces of human scent have been previously collected. Even though there is no standardized collection material for human scent samples across various law enforcement agencies cotton based materials are commonly used. The purpose of this study was to investigate the ability of different types of sorbent materials, mainly cotton and cotton blend materials, to trap and release a combination of volatile organic compounds (VOCs) previously reported as human scent compounds. Volatile Organic Compounds in the headspace of the samples were extracted and identifi ed using solid-phase micro-extraction gas chromatography / mass spectrometry (SPME-GC/MS). The results showed that cotton blend materials released signifi cantly greater amounts of polar compounds when compared to the pure cotton materials. It appears that the chemical composition of the materials rather than the surface morphology plays the greater role in governing the trapping and releasing capabilities of the materials for human scent collection.

Predation on toxic cane toads (Bufo marinus) may imperil bluetongue lizards (Tiliqua scincoides intermedia, Scincidae) in tropical Australia

Context. Detecting ecological impacts of invasive species can be extremely difficult. Even major population declines may be undetectable without extensive long-term data if the affected taxon is rare and/or difficult to census, and exhibits stochastic variation in abundance as a result of other factors. Our data suggest such a situation in an iconic Australian reptile species, the bluetongue lizard. Originally restricted to Central and South America, cane toads (Bufo marinus) are rapidly spreading through tropical Australia. Most native predators have no evolutionary history of exposure to the toads’ distinctive chemical defences (bufadienolides), and many varanid lizards, elapid snakes, crocodiles and marsupials have been killed when they have attempted to consume toads. Aims. Scincid lizards have not been considered vulnerable to toad invasion; however, one lineage (the bluetongues, genus Tiliqua) consists of large omnivores that may be affected. Our field and laboratory research aimed to elucidate this concern. Methods. Nightly surveys for bluetongue lizards (Tiliqua scincoides intermedia) and cane toads were conducted along two adjacent roadways on the Adelaide River floodplain of the Northern Territory. Scent discrimination trials in the laboratory assessed lizard responses to chemical cues from three food types (native frogs, cane toads and ‘preferred foods’) by counting tongue-flicks and biting elicited by cotton swabs. A subset of lizards was presented with live toads. Key results. Numbers of bluetongues encountered during standardised field surveys in the Darwin region declined soon after toads arrived, and we have not recorded a single lizard for the last 20 months. In the laboratory, foraging responses of bluetongues were as intense to cane-toad scent as to the scent of native frogs, and many of the lizards we tested attempted to consume toads, and were poisoned as a result. Conclusions and implications. The population decline of bluetongues in this region appears to have been the direct result of fatal ingestion of toxic cane toads. Our studies thus add a scincid lizard species to the list of native Australian predators imperilled by cane-toad invasion, and point to the difficulty of detecting invader impact even for an iconic species in a system subject to detailed survey work.

Neural correlates of behavior in the mothManduca sextain response to complex odors

WithManduca sextaas a model system, we analyzed how natural odor mixtures that are most effective in eliciting flight and foraging behaviors are encoded in the primary olfactory center in the brain, the antennal lobe. We used gas chromatography coupled with multiunit neural-ensemble recording to identify key odorants from flowers of two important nectar resources, the desert plantsDatura wrightiiandAgave palmeri, that elicited responses from individual antennal-lobe neurons. Neural-ensemble responses to theA. palmerifloral scent, comprising >60 odorants, could be reproduced by stimulation with a mixture of six of its constituents that had behavioral effectiveness equivalent to that of the complete scent. Likewise, a mixture of three floral volatiles fromD. wrightiielicited normal flight and feeding behaviors. By recording responses of neural ensembles to mixtures of varying behavioral effectiveness, we analyzed the coding of behaviorally “meaningful” odors. We considered four possible ensemble-coding mechanisms—mean firing rate, mean instantaneous firing rate, pattern of synchronous ensemble firing, and total net synchrony of firing—and found that mean firing rate and the pattern of ensemble synchrony were best correlated with behavior (R= 41% and 43%, respectively). Stepwise regression analysis showed that net synchrony and mean instantaneous firing rate contributed little to the variation in the behavioral results. We conclude that a combination of mean-rate coding and synchrony of firing of antennal-lobe neurons underlies generalization among related, behaviorally effective floral mixtures while maintaining sufficient contrast for discrimination of distinct scents.

The Stability of Collected Human Scent Under Various Environmental Conditions*,†

Human scent evidence collected from objects at a crime scene is used for scent discrimination with specially trained canines. Storage of the scent evidence is usually required yet no optimized storage protocol has been determined. Storage containers including glass, polyethylene, and aluminized pouches were evaluated to determine the optimal medium for storing human scent evidence of which glass was determined to be the optimal storage matrix. Hand odor samples were collected on three different sorbent materials, sealed in glass vials and subjected to different storage environments including room temperature, -80 degrees C conditions, dark storage, and UVA/UVB light exposure over a 7-week period. Volatile organic compounds (VOCs) in the headspace of the samples were extracted and identified using solid-phase micro-extraction-gas chromatography/mass spectrometry (SPME-GC/MS). Three-dimensional covariance mapping showed that glass containers subjected to minimal UVA/UVB light exposure provide the most stable environment for stored human scent samples.

Familiarity and phenotypic similarity influence kin discrimination in the social rodent Octodon degus

To evaluate the two most widely accepted mechanisms of kin recognition, prior association and phenotype matching, we studied kin discrimination in the South American hystricognath rodent Octodon degus. We first assessed differential treatment towards kin during paired encounters in an experimental arena (experiment 1). In addition, we used the habituation technique to investigate odour kin discrimination (experiment 2). In both experiments the relative influence of familiarity and phenotypic similarity were assessed using familiar and unfamiliar siblings, half siblings and genetically unrelated individuals. The results showed that O. degus treat conspecifics differentially as a function of familiarity; young reared apart were equally likely to explore each other independently of genetic relatedness. However, the exploratory behaviour of siblings reared apart and siblings reared together did not differ (experiment 1). On the other hand, degus did discriminate between odours of siblings, half siblings and unrelated individuals reared apart, and between odours of unrelated individuals reared together. Subjects did not discriminate between scents of their siblings reared together with them (experiment 2). These results suggest that familiarity is important in the interaction between animals and in the discrimination of conspecific scents. Nevertheless, our results suggest that phenotypic similarity may also influence social interactions and scent discrimination, although only between close kin, hence possibly influencing communal nesting. We propose that no single mechanism exclusively explains kin discrimination in degus. The prior association recognition mechanism mediated most instances of kin recognition, but phenotype matching is also used in close kin discrimination.

The Use of Bloodhounds in Determining the Impact of Genetics and the Environment on the Expression of Human Odortype

Bloodhounds are used to trail fleeing felons and missing persons. In order to start a trail, the dog must be presented with a person's scent. There are many hypotheses on what a bloodhound smells while trailing. The present study attempts to identify whether human scent is genetic, and if it is influenced by one's environment. Bloodhounds trained in human scent discrimination were used to differentiate between monozygotic twins, related and nonrelated persons, living together and apart. The first test required the dogs to run blind trails after being presented with the scent of one person in the pair, while the opposite person was hidden. The second test allowed the dogs to trail one person in the pair after both people were hidden. Results appear to demonstrate that bloodhounds rely heavily on genetic cues when differentiating between people. Environmental cues do not appear to significantly aid the bloodhound in scent discrimination.

Intensity and the ratios of compounds in the scent of snapdragon flowers affect scent discrimination by honeybees (Apis mellifera)

Floral scent is used by pollinators during foraging to identify and discriminate among flowers. The ability to discriminate among scents may depend on both scent intensity and the ratios of the concentrations of the volatile compounds of a complex mixture rather than on the presence of a few compounds. We used four scent-emitting cultivars of snapdragon (Antirrhinum majus) to test this hypothesis by examining the ability of honeybees to differentiate among their scents. Each cultivar produced three monoterpenes (myrcene, E-beta-ocimene, and linalool) and five phenylpropanoids (methylbenzoate, acetophenone, dimethoxytoluene, cis-methylcinnamate, and trans-methylcinnamate). Cultivars were reliably classified by their scents in a canonical discriminant analysis. Honeybees were unable to discriminate among the scents of flowers of the same cultivar in our assay. The ability of honeybees to discriminate among the scents of different cultivars was a function of the intensity of the floral scent. Discrimination was also correlated to the distance among the scents described by the discriminant analysis; the cultivars that had the greatest differences observed in the discriminant analysis were the easiest to discriminate. Our results show that honeybees are capable of using all of the floral volatiles to discriminate subtle differences in scent.