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

Stingless bees engage in a range of visually guided behaviours that require relatively high spatial resolution and contrast sensitivity. Although the eyes of honeybees, bumblebees, carpenter bees, and sweat bees have been studied extensively, there is limited knowledge of stingless bees. Here, we studied two sympatric Australian species, Tetragonula carbonaria and Austroplebeia australis, which are important crop pollinators. The bigger A. australis had more and larger ommatidial facets compared to T. carbonaria. Using pattern electroretinography, we showed that A. australis had higher contrast sensitivity (13.07) compared to T. carbonaria (5.99), but their spatial resolving power did not differ (0.53 cycles deg^-1). We discuss these differences in visual physiology in the context of the distinct foraging behaviours of the two species.

The various cone opsin genes are responsible for distinct ecological tasks, with the altered expression profiles in teleost fishes representing an excellent paradigm for studying how fishes can quickly adapt to diverse habitats within their lifecycles. The molecular mechanisms underlying transcriptional switching among cone opsin genes are still being investigated, but factors such as light conditions, developmental stages, sex hormones, and diet are known to play a role in changing cone opsin expression profiles. Based on previous research on guppies, we hypothesized that a diet rich in carotenoids could enhance expression of the opsin gene LWS in western mosquitofish (Gambusia affinis) and potentially influence female mate choice. We raised female western mosquitofish under low-level or high-level carotenoid diets and then conducted female mating preference experiments, with or without the presence of male guppy (Poecilia reticulata). qPCR revealed that high carotenoid intake upregulates SWS1 rather than LWS transcription. This positive feedback loop may promote foraging efficiency and also protect the visual system from UV damage. The carotenoid diets had no effect on pregnancy likelihood, possibly because UV light is not a critical cue in western mosquitofish female mate choice and/or the light source we used did not encompass the UV spectrum. Presence of male guppies had no effect on pregnancy likelihood, though a previous study reported that it significantly reduced brood size. Therefore, interactions between male guppies and western mosquitofish likely reduces the number of copulations and/or disrupts parenting to reduce the number of offspring.

Ethanol has been consumed by humans since the dawn of civilization and, over the course of millennia, a wide variety of ethanol-rich drinks have been produced across cultures. Traditionally, it was believed that only humans voluntarily consume ethanol and become inebriated by it. However, a growing amount of evidence is showing that several non-human animal species spontaneously consume ethanol in nature. Among these, there is the honey bee (Apis mellifera), which can find ethanol in decaying fruits and in the fermented nectar of flowers. Importantly, honey bees represent a useful animal model of ethanol consumption as, like humans, they voluntarily consume ethanol, they show acute dose-dependent motor and postural signs of inebriation, they display ethanol-induced disruption of cognitive functions and social behavior, and they develop ethanol dependence. Moreover, they are small, easy to acquire and easy to maintain in the laboratory. Finally, we possess a vast database of information on their natural history, physiology, genetics and behavior, with their ethogram comprising a wide variety of basic to complex behaviors, including the capacity to self-administer large quantities of ethanol. The present article reviews what is currently known about the physiological and behavioral pharmacology of ethanol in honey bees. The topics covered include the effect of ethanol on gene expression, epigenetic changes of DNA, neuronal stress, posture, locomotion, learning (comprising classical and operant conditioning), communication, social feeding (trophallaxis), aggression and foraging-related decision-making in honey bees.

Ants are known for their sophisticated navigational abilities and rely on various cues to locate food sources efficiently. Visual landmarks play a crucial role in guiding foraging behavior. However, the significance of walking ants perceiving the relative motion of a landmark to themselves during learning is still not fully understood. Here, Japanese carpenter ants were observed on a treadmill device where they could walk in place on the treadmill. Two types of conditions were set for the training process: the fixed condition involved a stationary landmark, and the moving condition featured a landmark oscillating at a constant speed from side to side after feeding, which was independent of the movements of the ants. In the Y-maze test, a significantly greater number of ants in the moving training condition associated the landmark with food (82% of the ants) than in the fixed training condition (56% of the ants). Our results thus suggest that perceiving the relative movement of landmarks during the learning process on a treadmill is important for ant foragers.

Chemosensation plays an important role in a wide range of behaviors including host identification and localization, oviposition site selection, and mate recognition. Variation in the ability to detect chemical signals may influence behavior in animals like insects that use volatile cues emitted from plants when discriminating between potential hosts. Differences in odor detection has been demonstrated to play a crucial role in driving changes in host use within and between insect species, leading to reproductive isolation between populations and eventual speciation through specialized host adaptation. We examined between-species variation in odor tuning and asked whether it is linked to shifts in host plant use in the Drosophila repleta species group, a taxonomic radiation of flies specializing on cacti that exhibits multiple shifts in host plant use across their phylogeny resulting in three current states: (1) Opuntia cactus specialists, (2) columnar cactus specialists, and (3) cactus "generalists" which use both hosts. We measured odor response profiles from select olfactory sensillar subtypes across multiple species within the group as well as for the outgroup D. melanogaster. Variation in both sensitivity and specificity to odors was observed, with some olfactory sensory neurons exhibiting differences associated with host cactus use. This study is the first in-depth analysis of the olfactory system across the repleta species group and provides the opportunity to test for conserved mechanisms in the olfactory system underlying divergence and host shift.

Exposure to dim light at night (dLAN) affects circadian rhythms and disrupts sleep and metabolism. However, given differential light sensitivity of circadian rhythms during early and late hours of the night, dLAN may have dissimilar detrimental effects in two halves of the night. If so, the disruptive effects of dLAN would be mitigated at different levels if one of the two halves of the night were replaced by complete darkness. We investigated this using both sexes of diurnal zebra finches that were exposed for three weeks to 12 h light (~ 150 lx) coupled with 12 h dark (0 lx), dLAN (5 lx), and half-dark and half-dLAN (6 h dark + 6 h dLAN, or vice versa) nights. dLAN disrupted the nocturnal sleep (shorter sleep bouts, reduced nocturnal sleep with frequent awakenings), and impaired glucose and fat metabolism as evidenced by body fattening and concurrent increase in g6pc, irs1 and star, and decrease in glut5 and sirt1 gene expressions in the liver. The substitution of half of dLAN with complete darkness mitigated much of the negative effects, with a much better alleviative response when the imposed darkness period covered the first half of the 12 h 'dLAN' night. Notably, the mitigation effects of darkness period were sex dependent. These results provide insights into differential temporal sensitivity of the night to negative impacts of the emerging 'light pollution' threat in an over-lit urban environment.

Terrestrial molluscs living in temperate and polar environments must contend with cold winter temperatures. However, the physiological mechanisms underlying the survival of terrestrial molluscs in cold environments and the strategies employed by them are poorly understood. Here we investigated the cold tolerance of Ambigolimax valentianus, an invasive, terrestrial slug that has established populations in Japan, Canada, and Europe. To do this, we acclimated A. valentianus to different environmental conditions (differing day lengths and temperatures), then exposed them to sub-zero temperatures and measured overall survival. Then, we measured low molecular weight metabolites using ¹H NMR to see if they play a role in their cold tolerance as they do in other invertebrate species. We found that A. valentianus is not strongly freeze tolerant but does become more cold-hardy after acclimation to shorter day lengths. We also found that no metabolites were strongly upregulated in response to winter conditions despite the change in cold hardiness, and instead saw evidence of metabolic suppression leading up to winter such as formate and L-glutamine being suppressed in winter conditions.

Monoaminergic neurotransmitters are essential for a multitude of physiological and behavioral functions including territoriality and parental care. The Puerto Rican coquí frog, Eleutherodactylus coqui, possesses an intriguing multi-modal male behavioral organization whereby males can be territorial, paternal, and silent (non-calling). The objective of this study was to quantify central monoamines in the three male modes and integrate this neurochemistry with data from microhabitat shelter selection and male social structure. Males were assessed for monoamines and metabolites using high performance liquid chromatography with electrochemical detection. Results indicated that there are distinct and significant differences among the three male behavioral modes based on male social structure, microhabitat shelter selection, and neurochemistry. Silent males are non-combative, quiescent, occur nocturnally in relatively open locations with sparser vegetation, and are characterized by high levels of epinephrine and norepinephrine in several forebrain nuclei. Territorial males emit vocalizations, are typically surrounded by more vegetation than silent males, may have a silent male within their territory, and are denoted by significantly higher levels of norepinephrine in the preoptic area and ventral hypothalamus and dopamine in the amygdala responsible male territorial behaviors. Paternal males brood and guard developing embryos in secluded nest sites that are surrounded by vegetation, not within territories of residential males, and typically not in close proximity of silent males. Paternal brains have significantly higher levels epinephrine and serotonin in the raphe and reticular nuclei indicating the necessity to regulate metabolic processes and stress during the period of prolong paternal care.

Courtship behavior in the polka-dot wasp moth Syntomieda epilais is the most elaborate acoustic communication system known in the Erebidae. Both males and females must emit their acoustic signals for successful mating under natural conditions in the presence of insectivorous echolocating bats. I stimulated ninety-two females S. epilais during their courtship period (between 2:30 and 6:30 am) with playback of conspecific male and female signals and of the Mexican free-tailed bat (Tadarida brasiliensis) attack sequence. I recorded the acoustic responses of the tested females. On the third night after eclosion, at the initiation of courtship behavior, females discriminate among these three types of acoustic trains, responding preferentially to conspecific male signals. In contrast, during the first two nights after eclosion, they respond strongly to the bat attack sequence but not to conspecific male signals. I also demonstrate that after mating (six nights after eclosion) female moths stop responding to conspecific male signals, while continuing to respond to the bat attack pulse-train. These, as well as other novel observations suggest that these female moths can modulate their acoustic signals according to the stimulating conditions for defense against bats or courtship, by varying their response thresholds and latencies.

Path integration is a key navigation mechanism used by many animals, involving the integration of direction and distance of path segments to form a goal vector that allows an animal to return directly to its starting point. While well established for animals walking on solid ground, evidence for path integration in animals moving without ground contact, such as flying insects, is less clear. The review focuses on flying Hymenoptera, particularly bees, which are extensively studied. Although bees can use flight distance and direction information, evidence for genuine path integration is limited. Accurately assessing distance travelled is a major challenge for flying animals, because it relies on optic flow-the movement of visual patterns across the eye caused by locomotion. Optic flow depends on both the animal's speed and the spatial layout of the environment, making it ambiguous for precise distance measurement. While path integration is crucial for animals like desert ants navigating sparse environments with few navigational cues, we argue that flying Hymenopterans in visually complex environments, rich in objects and textures, rely on additional navigational cues rather than precise path integration. As they become more familiar with an environment, they may iteratively refine unreliable distance estimates derived from optic flow. By combining this refined information with directional cues, they could determine a goal vector and improve their ability to navigate efficiently between key locations. In the case of honeybees, this ability also enables them to communicate these refined goal vectors to other bees through the waggle dance.