Journal of Comparative Physiology A-Neuroethology Sensory Neural and Behavioral Physiology最新文献

The naked mole-rat (NMR, Heterocephalus glaber) is a subterranean rodent that exhibits a range of unusual physiological traits, including diminished inflammatory pain. For example, nerve growth factor (NGF), a key inflammatory mediator, fails to induce sensitization of sensory neurons and thermal hyperalgesia in NMRs. This lack of NGF-induced neuronal sensitization and thermal hyperalgesia results from hypofunctional signaling of the NGF receptor, tropomyosin receptor kinase A (TrkA). Like NGF-TrkA signaling, the neurotrophic factor artemin, a member of the glial cell line-derived neurotrophic factor (GDNF) family, is implicated in mediating inflammatory pain through its receptor, GDNF family receptor α3 (GFRα3), which is expressed by a subset of dorsal root ganglia (DRG) sensory neurons. Here we investigated GFRα3 expression in DRG neurons of mice and NMRs, as well as measuring the impact of artemin on DRG sensory neuron function in both species in vitro. Using immunohistochemistry, we observed a similar abundance of GFRα3 in mouse and NMR DRG sensory neurons, high coexpression with the transient receptor potential vanilloid 1 (TRPV1) ion channel suggesting that these neurons are nociceptive neurons. Using in vitro electrophysiology to record from cultured DRG sensory neurons, we observed that artemin induced depolarization of the resting membrane potential and decreased the rheobase in both species, as well as diminishing the degree of TRPV1 desensitization to multiple capsaicin stimuli. Overall, results indicate that artemin similarly sensitizes sensory neurons in both mice and NMRs, future in vivo studies being required to confirm if the conserved in vitro sensitization also occurs in vivo.

Goal-oriented learning and navigation is well known in eusocial insects. The solitary foraging of nocturnal bull ants Myrmecia midas in their visually complex environment relies on path integration and landmark learning. While this species seems to be 'sensitive' to handling and reacts to visual changes in their surroundings, not much is known about how added olfactory stimuli impact their route navigation on a vertical surface. In the current study, we added one of five different invisible odours on the trees on which foragers normally forage. We found that the bull ants showed phobic responses to all the odours. The Tea-tree and Lavender odours showed the strongest impact on the bull ants' navigation by causing detours, U-turns, and avoidance of the sensory stimuli, with the ants meandering more and scanning more frequently. The odours of Olive oil, Flax-seed oil, and Eucalyptus oil had a moderate impact on the ants' navigation. These findings showed the widespread influence of non-visual chemical cues in shaping bull ant navigation, reactions that we interpret as neophobic responses stemming from chemical alterations on learned routes. A second experiment supported the interpretation of neophobia as opposed to an inherent aversion to the odours. Repeated exposure to Lavender led to reduced aversive responding. Overall, this study contributes to the understanding of the effects of foreign odours, adding to our understanding of the complex learning processes of bull ants in their vertical navigation.

Male sea lamprey (Petromyzon marinus) release a sex pheromone featuring a potent bile acid 3-keto petromyzonol sulfate (3kPZS), which plays a critical role in attracting ovulated females to spawning sites during their terminal reproductive phase. In this study, we evaluated how systematic modifications of 3kPZS, referred to as the 11 analogs that retain the 3kPZS core structure with one or more functional group substitutions, affect female sea lamprey neurophysiological and behavioral responses to 3kPZS. Using electro-olfactogram recordings and two-choice flume behavioral assays, we characterized responses elicited by each analog and assessed whether the analogs interfered with 3kPZS-induced responses. Our results demonstrate that bile acid analogs with substitutions of hydroxyl or ketone groups with sulfate moieties at carbon positions 3, 7, 12, and 24 elicit distinct olfactory and behavioral responses in sea lamprey. Analogs with a sulfate group at the carbon-24 position tended to elicit potent olfactory responses of comparable magnitude to 3kPZS. Adding more sulfates at the carbon-3, 7, or 12 position altered behavioral valence and often neutralized or reversed female attraction to 3kPZS in a flume. These data elucidate structure-activity relationships and identify key structural determinants underlying sea lamprey olfactory detection and odorant-mediated behavioral responses. The findings may inform a potential approach for managing invasive sea lamprey populations in the Laurentian Great Lakes by disrupting bile acid mediated pheromone communication. Further research is needed to assess the utility of these compounds in natural stream environments and to refine the structural features of these pheromone antagonists to enhance their efficacy.

Chemical sensing of the surrounding environment is crucial for many aspects of bivalve biology, such as food detection and predator avoidance. Aquatic organisms strongly depend on chemosensory systems; however, little is known about chemosensory systems in bivalves. To understand how the carpet shell clam (Ruditapes decussatus) senses its surrounding chemical environment, we used an electrophysiological technique - the electro-osphradiogram - to assess the sensitivity of the osphradium to different putative odorants (amino acids, bile acids) and odours (predator-released cues and signals from con- and heterospecific bivalves). The clam osphradium was sensitive to most proteinogenic L-amino acids, evoking negative, tonic, and concentration-dependent responses. However, acidic amino acids (L-glutamic and L-aspartic acid), L-arginine and bile acids (cholic, taurocholic and taurolithocholic acid) failed to evoke any response. Surprisingly, while cues from injured bivalves (con- and heterospecific) evoked strong responses, predator-released cues (green crab, Carcinus maenas) failed to elicit any response, whether fed or unfed. That predator-released cues failed to evoke an electrophysiological response in the clam osphradium may indicate that they use cues released by injured prey - alarm cues - to avoid predation and/or that predators are detected by different sensory modalities. Indeed, the behavioural assays, performed to understand how clams make use of such sensory inputs, revealed that the activity index decreased after exposure to water conditioned with injured conspecifics, suggesting the origin of such alarm cues. Further research is needed to identify the chemical nature of these cues. We suggest that the electro-osphradiogram will be a useful tool in this endeavour.

Endothermic insects including bees, butterflies, and moths need to warm up their flight muscles before taking flight. For instance, diurnal butterflies bask in the sun to heat their flight muscles, whereas nocturnal hawkmoths display a pre-flight shivering behavior in which small-amplitude wing movements cause flight muscles to warm up, eventually generating large-amplitude wing motion for flight. The time required for warm-up puts such insects at considerable risk if they need to rapidly escape from predators. Here, we show that upon experiencing a sudden air-puff on the head, hawkmoths with lower thoracic temperatures can rapidly initiate flight without the need for pre-flight shivering. This response is mediated by mechanosensory cephalic bristles that are located beneath the scales on their head. When activated, these bristles trigger a set of flight-related reflexes including antennal positioning, foreleg extension, wing movement, and abdominal flexion. Some of the mechanosensory neurons associated with the cephalic bristles arborize in the subesophageal zone (SEZ) and antennal motor and mechanonsensory centre (AMMC), whereas most arborize in pro-, meso- and meta-thoracic ganglia, which contain the motor circuitry for foreleg motion, flight, and abdominal flexion. Thermal recordings revealed that large-amplitude flapping following cephalic bristle-stimulation occurs at lower thoracic temperatures than required for endogenously-initiated take off. Electromyogram recordings from steering and indirect flight muscles show significant variability in activation latency in response to cephalic bristle stimuli. The range of latency values among different muscles overlaps, suggesting that cephalic bristle stimulation broadly activates indirect flight and steering muscles, thereby generating high-amplitude wing movement at lower thoracic temperatures. Thus, akin to locusts, the cephalic bristle system in hawkmoths rapidly triggers flight upon sensing danger, ensuring swift escape from potential threats.

The waving behavior exhibited by some species of male mudflat-dwelling crabs is characterized by rhythmic claw movement, which is considered to be a form of courtship toward females and agonism toward males. A fascinating aspect of the waving behavior is that its rhythm is synchronized with that of the surrounding males. To elucidate the behavioral mechanism underlying the synchronization of the waving rhythm in the dotillid crab (Ilyoplax pusilla), we conducted a laboratory experiment using a waving-mimicking robotic model. When a single robot was operated continuously at a certain frequency (0.91-1.66 Hz) in front of a burrow-holding male, the crab responded to the robot with corresponding waving. In cases of relatively slow operating frequencies (≤ 1.11 Hz), the crabs tended to perform synchronous waving at a timing that preceded the robot. In contrast, when the operating frequency was relatively high (≥ 1.25 Hz), they waved synchronously with the robot with almost no time lag. The crabs tended not to wave at the same frequency as the high-frequency robot but waved once every two or three movements of the robot. These results suggest that synchronous waving without delay occurs in situations where the waving frequency increases competitively among neighboring males. The crabs may also adjust their waving frequency to half or one-third of that of high-performance opponents while maintaining their waving to avoid delays.

The brinjal shoot and fruit borer, Leucinodes orbonalis Guenée, inflicts significant yield losses in brinjal, often resulting in the extensive use of insecticides. Development of insecticide resistance and ecological concerns demand safer and species-specific alternatives. This study examines plant-derived volatile organic compounds (VOCs) as potential semiochemicals for its management. The present study employed electroantennography (EAG) to examine the summated neuronal response in the antennal of unmated male and female L. orbonalis moths to host plant VOCs. Both male and female antennae showed higher response when exposed to nonanal, α-terpineol, 2-ethyl-1-hexanol, linalool, methyl salicylate, and phenylacetaldehyde, with females showing greater sensitivity than males. The behavioral assays using a Y-tube olfactometer demonstrated significant attraction of moths towards 2-ethyl-1-hexanol, benzaldehyde, and phenylacetaldehyde. To further substantiate these findings, molecular docking studies were conducted using homology models of general odorant-binding proteins (GOBPs: GOBP1, GOBP2, and GOBP3) of L. orbonalis. Protein models were constructed through MODELLER, validated for structural accuracy, and docked with selected VOCs obtained from PubChem using AutoDock Vina. Among the three proteins, GOBP2 displayed the strongest and broadest ligand-binding affinities, followed by GOBP3 and GOBP1. Notably, high-affinity interactions with 2-ethyl-1-hexanol, benzaldehyde, and phenylacetaldehyde were characterized by π-π stacking, van der Waals forces, and hydrophobic bonding. The docking outcomes correspond closely with EAG and behavioral results, underscoring the potential of these VOCs as eco-friendly semiochemicals based management of L. orbonalis.

In 1973, the Nobel Prize for Physiology or Medicine was awarded to Karl von Frisch, Konrad Lorenz, and Nikolaas Tinbergen for their pioneering work in the development of Ethology. This branch of science, which involves the study of animal behaviour, differs from others due to its emphasis on the behaviour of animals in their natural environment. We hypothesized that freshly collected wild Lymnaea stagnalis would be capable of demonstrating a form of conditioned taste aversion and memory in natural pond water, both at the pondside and in the lab. We further hypothesized that the snails would demonstrate similar learning and memory formation in laboratory-made pond water, both at the pondside and in the lab. The associative learning shown occurs between two stimuli, a stressor and a food substance, when they are experienced together over a 45-min period. Here, we demonstrate the similar learning and memory-forming capabilities of wild L. stagnalis, whether trained at the pondside or in the lab.

Despite their tiny size, lepidopterans accomplish some of the most extraordinary migrations on Earth. Monarch butterflies and bogong moths, for example, travel vast distances to find the same seasonal sheltering sites year after year, and remarkably do so without any prior experience. How do these delicate creatures navigate so precisely across large and changing landscapes? Scientists have spent decades unraveling this mystery, revealing that lepidopterans possess a sophisticated suite of navigational tools that rival those of much larger animals. Lepidopteran compass systems rely on celestial cues like the sun, stars, and polarized light, as well as the Earth's magnetic field. Diurnal monarchs and nocturnal bogong moths have become model species for understanding how insects combine skylight and magnetic compasses to find their way. Recent discoveries have shed light on the neural circuits and genetic blueprints that power these compasses. In this review, we provide an overview of the navigational toolkit employed by lepidopteran migrants, dive into their mechanisms, and highlight future directions needed to fully decode the secrets of insect long-distance navigation.

Migratory birds have evolved a multitude of physiological and behavioural adaptations to reach their population-specific wintering areas during their first migration. The endogenous program encodes distance, direction and fuelling, and involves species-specific adaptations leading naïve migratory birds along highly diverse routes. While daylength has been extensively studied in relation to the onset of migration, its potential role in the transition out of the migratory phenotype remains largely untested. Here we study, by experimentally increasing the daylength in autumn simulating a temporal shift earlier in the season or a latitudinal displacement toward the wintering area as experienced later in the season after the autumn equinox, what effect a substantial photic treatment has on overall level and diel pattern of activity and fuelling in juvenile Eurasian reed warblers (Acrocephalus scirpaceus) migrating to tropical Africa. The treatment group experienced a 2h increase in daylength in the evening, while the control group was held in the local photoperiod in southern Sweden. The controls showed strictly nocturnal migratory restlessness starting immediately after sunset, while the treatment birds responded by delaying the onset of nocturnal migratory restlessness following the artificially delayed sunset, without changing the level of activity. Treatment birds increased fuelling initially, but then reduced it after one week in captivity, resulting in a lower fuelling rate as compared to the controls by the end of experiment. The reduced fuelling suggests treatment birds possibly interpreted the diel period as arrival to the wintering area. The results confirm the importance of photic information in regulating phenotypic expressions of migratory activity and fuelling in juvenile birds.