In a honey bee colony, the queen uses queen mandibular pheromone (QMP) to induce young worker bees to feed and groom her. Among its many behavioural and physiological effects, QMP reduces dopamine levels in the brains of young worker bees. Dopamine is a biogenic monoamine involved in numerous functions including motor control and aversive learning. This study investigates the effects of QMP on motor activities and aversive learning behaviour and the potential link between QMP and dopamine levels in the brain of young bees. In young bees under the age of 15-days, QMP dramatically reduced locomotor activity and inhibited aversive learning behaviour. Interestingly in older bees these behaviours were not affected by pheromone. Treating young bees with the dopamine precursor, L-dopa (3.25 [mu]g/mI), partially rescued the levels of locomotor activity in QMP-treated bees, and reduced QMP�s effects on aversive learning. This suggests that blocking effects of QMP on both locomotor activity and aversive learning result at least in part from QMP-induced changes in brain dopamine levels. Two components of the QMP blend, 4-hydroxy-3-methoxyphenylethanol (HVA) and methyl p-hydroxybenzoate (HOB) were examined more closely. Both HVA and HOB are structurally similar to dopamine. HVA was found to mimic the effects of the full QMP blend on aversive learning. Treating bees with HVA reduced aversive learning in young bees. In contrast, treatment with HOB did not affect learning ability. This strongly suggests that HVA is one of the key components that mediates the actions of QMP on aversive learning. The final section of this thesis investigates why it might be advantageous to honey bee queens to block aversive learning and reduce locomotor activity in young worker bees. The study reveals age-related differences in behaviours that individual worker bees display towards QMP. Young bees reared with QMP or collected from a queenright hive showed attraction to QMP. Conversely, older bees displayed avoidance behaviour towards QMP. By blocking the establishment of aversive memories, young bees may be prevented from forming an association between QMP and any unpleasant side effects induced by this pheromone. This may confer significant benefit to the queen by increasing the likelihood of young workers remaining in her attendance.

Odor signals mediate a variety of behaviors in animals across a diversity of taxa. Despite dramatic morphological differences between animals from different taxa, several important features of olfactory system organization and processing are similar across animals. Because of this similarity, a number of different organisms including mammals, insects, and decapod crustaceans serve as valuable model systems for understanding general principles of olfactory processing. As in other organisms, including both vertebrates and insects, the chemosensory system of decapod crustaceans is organized into multiple anatomically distinct neuronal pathways. The two main pathways (the aesthetasc/ olfactory lobe pathway and non-aesthetasc/ lateral antennular neuropil pathway) originate in different populations of antennular sensilla and project to different neuropils in the brain. The functional significance of this parallel organization is not well understood in crustaceans or in many other species. Although in some insect species the functions of parallel pathways are clearly delineated by the types of odors processed by each, functional differences between parallel pathways in other organisms are much less distinct. A critical step towards understanding the functional significance of the multiple chemosensory pathways is to identify the specific behaviors that are driven by each pathway. Using spiny lobsters and crayfish as model organisms, the importance of each pathway was examined in three different behavioral contexts: (1) orientation to a distant food odor, (2) shelter selection in response to conspecific chemical signals, and (3) determination of conspecific social status. In each study, selective ablations of specific populations of antennular sensilla were performed, and the behavior of ablated animals was compared to that of intact controls. Results show that either the aesthetasc or non-aesthetasc pathway is capable of driving orientation to food odors, suggesting functional redundancy between the pathways in this behavior. In contrast social odors are processed preferentially by the aesthetasc pathway rather than the non-aesthetasc pathway, suggesting a unique role for the aesthetasc pathway in this context. As in other organisms possessing multiple chemosensory pathways, the dual antennular pathways in crustaceans display both unique and overlapping functions depending on the chemicals examined, and the behavioral context in which the signal is presented.

Adult neurogenesis of olfactory receptor neurons (ORNs) occurs in diverse organisms including in decapod crustaceans. This dissertation describes the molecular, cellular, and physiological changes that occur during adult neurogenesis of ORNs in the antennular lateral flagellum (LF) of the spiny lobster Panulirus argus. Examination of the role of splash (spiny lobster achaete scute homolog) in adult neurogenesis and regeneration using in situ hybridization showed splash was not closely associated with the formation of sensory neurons under normal physiological conditions. Damage to the LF, which induces regeneration, enhanced splash expression, suggesting an association between splash with regeneration and repair. This study suggests that splash plays multiple roles in the olfactory organ of adult spiny lobsters. Examination of extracellular and intracellular Ca2+ in mediating spontaneous and odor-induced responses of ORNs, using calcium imaging showed that odor-induced Ca2+ transient responses and spontaneous Ca2+ oscillations in ORN somata are primarily mediated by an influx of extracellular Ca2+ through Co2+ -sensitive Ca2+ channels, but that intracellular Ca2+stores also have some contribution. These responses are independent of TTX-sensitive Na+ channels, suggesting that these Ca2+ responses may reflect receptor potentials. Examination of changes in odor specificity, sensitivity, and temporal responses in adult-born ORNs showed an increase in the percentage of odorant-responsive ORNs as they age from newly-born cells to mature, and a decrease in odorant-responsive ORNs as they senesce. As adult-born ORNs age, there was a decrease in the percentage of ORNs that undergo spontaneous Ca2+ oscillations and an increase in the amplitude of oscillation. ORNs became more broadly tuned as they senesce, and their response profile, defined by the most effective odorant, changed. Odor sensitivity changed with age. This study demonstrated that the physiological response properties of adult-born ORNs changed with functional maturation. Taken together, this dissertation reveals molecular, cellular and physiological changes in adult born ORNs and elucidates mechanisms of adult neurogenesis.

Thesis (Ph.D.)--University of Alberta, 2009. / A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy, Food Science and Technology, Department of Agricultural, Food, and Nutritional Science. Title from pdf file main screen (viewed on January 10, 2010). Includes bibliographical references.

The main focus of the current study was to quantify the chemical signals received by a blue crab (Callinectes sapidus) tracking a source in a laboratory flume. To make a direct linkage between tracking behavior and the odorant concentration signal, we developed a measurement system to quantify the instantaneous concentration field surrounding actively tracking blue crabs. A three-dimensional laser-induced fluorescence (3DLIF) system was designed and constructed to measure odorant concentrations around crabs tracking three source types: a continuous release with exit velocity matching the mean local velocity in the flume; a continuous release with a meander created by an upstream cylinder; and a pulsed release switching on and off and with the same mass flow rate as the other two plume types. The meandering and pulsed plumes were introduced to observe the effects of large-scale spatial (meandering) and temporal (pulsed) intermittency on crab tracking. Simultaneous with the chemical concentration measurements, crab position data was recorded for kinematic analysis during post-processing. In addition, concentration measurements were collected for the three plume types without crabs present in order to quantify the statistical characteristics of the plume structure The concentration signals arriving at the antennules and outer chemosensory organs, most notably the legs, were targeted due to the hypotheses that concentration bursts at the antennules mediate upstream movement and that spatial contrast at the leg chemosensors mediates turning. A sampling zone was placed in front of the crab's mouth parts and aligned with the crab carapace orientation to extract odorant bursts at the antennules. The data generally showed an increase in upstream walking speed when high concentration bursts arrive at the antennules location, which agrees with the hypothesis. Measurement of the odorant concentration at the outer chemosensors was less direct and involved placing a box upstream of the crab and sampled earlier in time in order to avoid shadowing interference. Based on the signal at the upstream sampling box, a general bias for turning was observed. Crabs casted transversely in response to the directional bias extracted from the upstream sampling box. A statistical analysis of crab behavioral response to concentrations at the antennules and outer chemosensors can be found in a (future) companion thesis written by Jennifer Page in the School of Biology. Data were also taken for the three plume types in the absence of blue crabs. The continuous plume average statistics displayed Gaussian behavior at nozzle centerline. The meandering plume data conformed to the meandering plume model of Gifford (1959), modified for an induced pseudo-periodic meander. The pulsed plume displayed characteristics intermediate between the cloud dispersion model (Townsend 1951, Chatwin and Sullivan 1979) and the Gaussian dispersion model for a continuous release. For the three plume types, the standard deviation of the concentration fluctuations was greater than the average concentrations, as time records consisted of intermittent high concentrations interspersed with concentrations close to zero.

In a honey bee colony, the queen uses queen mandibular pheromone (QMP) to induce young worker bees to feed and groom her. Among its many behavioural and physiological effects, QMP reduces dopamine levels in the brains of young worker bees. Dopamine is a biogenic monoamine involved in numerous functions including motor control and aversive learning. This study investigates the effects of QMP on motor activities and aversive learning behaviour and the potential link between QMP and dopamine levels in the brain of young bees. In young bees under the age of 15-days, QMP dramatically reduced locomotor activity and inhibited aversive learning behaviour. Interestingly in older bees these behaviours were not affected by pheromone. Treating young bees with the dopamine precursor, L-dopa (3.25 [mu]g/mI), partially rescued the levels of locomotor activity in QMP-treated bees, and reduced QMP�s effects on aversive learning. This suggests that blocking effects of QMP on both locomotor activity and aversive learning result at least in part from QMP-induced changes in brain dopamine levels. Two components of the QMP blend, 4-hydroxy-3-methoxyphenylethanol (HVA) and methyl p-hydroxybenzoate (HOB) were examined more closely. Both HVA and HOB are structurally similar to dopamine. HVA was found to mimic the effects of the full QMP blend on aversive learning. Treating bees with HVA reduced aversive learning in young bees. In contrast, treatment with HOB did not affect learning ability. This strongly suggests that HVA is one of the key components that mediates the actions of QMP on aversive learning. The final section of this thesis investigates why it might be advantageous to honey bee queens to block aversive learning and reduce locomotor activity in young worker bees. The study reveals age-related differences in behaviours that individual worker bees display towards QMP. Young bees reared with QMP or collected from a queenright hive showed attraction to QMP. Conversely, older bees displayed avoidance behaviour towards QMP. By blocking the establishment of aversive memories, young bees may be prevented from forming an association between QMP and any unpleasant side effects induced by this pheromone. This may confer significant benefit to the queen by increasing the likelihood of young workers remaining in her attendance.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Thesis (Ph. D.)--Georgia Institute of Technology, 2006. / Title from PDF t.p. (viewed on Oct. 28, 2006). Marc Weissburg, Committee Chair ; Mark Hay, Committee Member ; Lin Jiang, Committee Member ; David Dusenbery, Committee Member ; Don Webster, Committee Member. Includes bibliographical references (p. 115-122).

Chemoreception plays an important role in predator-prey interactions and feeding dynamics. While the chemoreception of attractant or pleasant tasting compounds has been well studied, aversive chemoreceptive signaling has been difficult to investigate behaviorally in an ecological context because these interactions are species- and context- specific and deterrent compounds vary among prey. Using the coral reef system, this thesis explores on a molecular level the deterrent mechanism underlying detection by fish predators of an aversive compound, in order to gain a greater understanding of predator-prey interactions in this community. Like other organisms that are sessile or slow-moving, marine sponges have special mechanisms for defense from predation, commonly containing aversive-tasting compounds that defend these organisms from predation. To this end, we sought to identify and characterize a fish chemoreceptor that detects one or more of these compounds. We isolated a single cDNA clone encoding RAMP-like triterpene glycoside receptor (RL-TGR), a novel co-receptor involved in the signaling of triterpene glycosides. This co-receptor appears to be structurally and functionally related to receptor activity-modifying proteins (RAMPs), a family of co-receptors that physically associate with and modify the activity of G protein-coupled receptors (GPCRs). Expression in Xenopus oocytes showed that it responds to triterpene glycosides in a receptor-mediated manner and requires co-expression of a GPCR to enable signaling in oocytes; both of these receptors may be components of a larger signaling complex. A 40 bp portion of the gene is conserved across multiple fish species, but is not found in any other organism with a sequenced genome, suggesting that the expression of this receptor is limited to fish species. RL-TGR is the first identified gene encoding a co-receptor that responds to a chemical defense. This finding may lead the way for the identification of many other receptors that mediate chemical defense signaling in both marine and terrestrial environments, as this protein has the potential to represent the first of an entire family of co-receptors that respond to aversive compounds.

It was long believed that humans were unable to utilise the odours of conspecifics to co-ordinate social interactions in ways in which other species appear to be capable. However, a surge in interest in human social olfaction has recently challenged this view. The numerous studies conducted in this area have found that multiple state and trait related cues can be detected in body odour. Furthermore, many studies indicate that women are often more sensitive to these cues, and that sensitivity can be associated with fertility, findings that are consistent with sex differences in reproductive effort and benefits of choosiness in mate-searching. Since previous studies in this area have usually addressed the potential for humans to use olfactory communication in a comparable manner to other mammals, they typically involve collection and assessment of ‘natural’ odour. That is, they explicitly exclude the possibility of ‘contamination’ of odour samples by artificial fragrances. However, humans have used artificial fragrances for millennia, across many different cultures. This raises the question of whether widespread fragrance use may affect or disrupt the detection of this information in modern humans. The first aim of this thesis was to address this question by investigating how fragrance use may mediate the detection of olfactory information in humans. As well as providing further evidence for sex differences in the assessment of olfactory cues, and for the role of olfaction in real world partner choice, the findings herein suggest that fragrance may act differently on different information being assessed, potentially masking accurate assessment of certain traits (such as masculinity), while fragrance choice and preferences may be important in complementing other olfactory information (such as the general distinguishability of an individuals’ odour profile). A second aim of the thesis was to develop a scale in order to more accurately describe the varying perceptual qualities of human body odour – in other words to map human body odours. This work was conducted alongside perfumers in order to benefit from their expertise in olfactory perception and semantic labelling of odours. The development of such a scale could enable improved understanding of the perceptual qualities of human odour, making it possible to link specific perceptual qualities to specific cues (e.g. symmetry, masculinity, sex) or to manipulate odours based on perceptual qualities in experimental settings, and has direct practical implications for fragrance designers and for improving the ability of individuals to choose fragrance products that suit their odour profile. The second section of the thesis focuses on the effects of odours on the individual wearer as well as on perceivers in the environment. One study is presented which investigates the role of malodour reduction compared to the addition of fragrances in perceptions of confidence and attractiveness, finding that both the reduction of malodour and the addition of fragrance appear to be important for confidence as rated by others in the environment. The final study presented in the thesis examines a hitherto un-investigated role of olfaction during human pregnancy. The rationale for the study is based on evidence suggesting that in certain non-human species, which also show bi-parental care of offspring, there may be a role for chemical, or odour based, communication which underpins behavioural and endocrinological changes related to infant care behaviours in males. The study found little evidence to support the presence of analogous olfactory signalling during human pregnancy, though the findings are discussed in light of methodological changes which, if made in future studies, may result in different outcomes. The thesis concludes with a discussion of the importance of continuing to investigate various forms of olfactory communication, as well as improving our understanding of odours through the mapping of their perceptual qualities, and finally further examining the ways in which various fragranced products, which are widely used in society, may affect all of this. Future directions for this area of research are discussed. This line of investigation will, I argue, enable us to finally establish the true role of olfaction in contemporary social environments.