As the Arctic warms and becomes more accessible to human activities and associated noise sources, it is important to understand the auditory capabilities of ice-associated marine mammals that rely on sound. In this study, the in-air hearing of one adult bearded seal (Erignathus barbatus) was measured in ambient outdoor conditions using psychophysical methods. 50% detection thresholds were measured for 10 frequencies (0.04-51.2 kHz) that extend across the subject's hearing range. For low to mid frequencies (0.04-12.8 kHz), thresholds were constrained, or masked, by ambient noise. Thresholds obtained at higher frequencies (25.6-51.2 kHz) were sufficiently elevated above background noise to provide absolute measures of hearing sensitivity. These measurements reveal that the high-frequency roll-off for bearded seals is in alignment with available auditory data for related species despite more than 11 million years of evolutionary isolation. Further, the data collected at low and mid frequencies enable an unconventional estimation of critical ratios, which can be applied in masking models. Collectively, these findings for bearded seals listening for airborne sounds highlight auditory similarities within the northern clade of phocid Carnivores and improve predictions of potential noise effects for seals in changing Arctic soundscapes.

The natural lighting conditions vary depending on latitude, niche, and time of day, and animals are evolutionarily adapted to them. Artificial lighting, along with global warming, drives population ranges toward high latitudes, which creates fast-changing environments for the biota. The American cockroach Periplaneta americana L. is a synanthropic species with a nocturnal lifestyle, rarely exposed to light. Three-month-long exposure to constant light or constant darkness compared to the control 12:12 h day and night cycle, causes behavioral changes explained by two main factors: adaptation of the visual system and circadian rhythm disruption. State of complete immobility, an indicator of the inactive phase of a 24 h rhythm, appeared in groups kept under constant light regimes and tested in the dark, as well as in those subjected to experimental lighting with low-intensity green light. Exposure to such light caused different behavioral changes in groups kept under different light regimes, reflecting the cockroaches' internal levels of arousal, stress, and light adaptation of their photoreceptor organs. Thus, altered lighting conditions impose significant challenges on different aspects of insect physiology and behavior.

Delayed-rectifier voltage-gated K conductances (I) can confer band-pass properties to the membrane impedance gain function in the frequency domain, and shorten the duration of transient receptor potentials evoked by voltage-insensitive receptor currents in the time domain. Here, by investigating in silico the underlying mechanisms, we found that: 1. I activation rate was the major determinant of both the voltage response narrowing and the impedance gain peaking. Both effects were non-linear, voltage-dependent, with the maxima determined by I conductance and kinetics. 2. Analysis in the time domain revealed that for efficient modulation, the kinetics of I must correspond to that of the receptor current: slower-activating Is more strongly narrowed voltage responses elicited by slower receptor currents than faster-activating Is, and vice versa. 3. Two complementary mechanisms mediated the modulation: (1) voltage amplification at the onset of receptor current during a window of relatively high resistance due to delayed activation of I, and (2) attenuation of voltage response during its decay by excessive I due to its delayed deactivation. Consequently, the action of I caused a partial leftward shift of voltage waveform relative to the receptor current, resembling the effect of electrical inductance. 4. Voltage response narrowing was opposed by self-shunting of the depolarizing receptor current as it increased. Consequently, the increase in corner frequency due to I was limited to small voltage responses. Our results elucidate reciprocal relationships between the voltage response and I, and the conditions when I can confer band-pass properties to impedance gain function.

Many insects are formidable navigators illustrated by homing behavior in bees and ants or regular seasonal migrations in butterflies, moths, and others. For spatial orientation, many insects rely on celestial cues, in particular the position of the sun or the polarization pattern of the blue sky generated by the sun. In all species studied celestial polarization is perceived by photoreceptors in a highly specialized dorsal rim area of the eye. Studies in various insects showed that the central complex utilizes these and other sensory inputs to create an internal compass-like representation of external space for vector navigation. Cockroaches, likewise, rely on visual and antennal input for navigational decisions mediated by the central complex. To explore the possible contribution of sky compass signals, we have characterized the responsiveness of neurons of the optic lobe and central complex of the Madeira cockroach Rhyparobia maderae to the angle of polarized light and the azimuth of unpolarized light spots representing the sun or the chromatic gradient of the sky. Strong responses to polarization angle and to changing polarization angle were found in several cell types connecting both optic lobes. Responses to sky compass signals in neurons of the central complex were less pronounced, but were significant in several cell types corresponding to neurons encoding sun compass signals in other species. Although the Madeira cockroach is a nocturnal scavenger and the existence of a specialized dorsal eye region has not been established, sky compass signals likely play a substantial role in behavioral decisions.

Caterpillars (larval Lepidoptera) are one of the most ecologically and evolutionarily significant taxa on Earth. As both feeders and food, they shape the dynamics of enumerate ecosystems on land. Key to this prominent role in nature is the sensory systems that inform, guide, and trigger their behaviour. Gaining an understanding of caterpillar sensory ecology therefore promises to reveal fundamental insights into the broader principles of ecology and evolution, conservation and management, within and beyond the Lepidoptera. To facilitate such an understanding, here we review the existing literature on the sensory physiology and ecology of all currently recognised sensory modalities in caterpillars, namely vision, hearing, vibration detection, touch, electroreception, chemoreception, hygroreception, thermoreception, and graviception. In each of these sensory modalities, we also explore the current evidence surrounding the threat of anthropogenic sensory pollution. Taken together, this review reveals the great depth and breadth of research into caterpillar sensory ecology, making clear the value of caterpillars to neuroethology, but also of neuroethology to caterpillars. However, many of the attributes that caterpillars bring to neuroethological research are yet to be taken advantage of. For example, there is currently a lack of comparative sensory system studies on caterpillars, utilising their ecological diversity and existing phylogenetic data. We also highlight many considerable knowledge gaps, most pertinently, the need to identify the sensors responsible for each sensory modality in caterpillars, and to characterise the potential effects of sensory pollution across all of these modalities.

The Lepidoptera, butterflies and moths, display an astonishing diversity of spatial orientation strategies essential for survival, reproduction, and ecological success. These spatial orientation strategies range from basic taxes to light, wind, gravity, and chemical cues, to more advanced strategies such as straight-line dispersal, multigenerational migration across continents, and complex trap-lining foraging involving long-term spatial memory. These orientation behaviours are tightly integrated with the ecological roles of lepidopterans as pollinators, prey, and bioindicators, and are supported by a flexible neuronal network. Of special interest for successful orientation are higher-order integration centres like the mushroom bodies (centres for learning and memory) and the central complex (the centre for spatial orientation and locomotion). These centres support cue integration, compass orientation, memory, and directional decision-making. However, anthropogenic stressors, including habitat fragmentation, light pollution, pesticides, and electromagnetic noise, threaten both the environmental cues and the neural systems facilitating lepidopteran navigation, with potential cascading effects on biodiversity and ecosystem health. By combining insights from behavioural ecology, neurobiology, and conservation, we aim to provide a comprehensive overview of the challenges and adaptations that shape the navigational toolkit of lepidopterans, underlining their significance as animal models for studying spatial orientation in a changing world.

Praying mantises often display elaborate camouflage, disappearing into the shapes, textures, and colors around them. But they have largely been thought to be monochromats, unable to perceive the colors they mimic. To examine this, we tested the compound eye spectral sensitivity of three species of praying mantises, each representing unique mimicry strategies: Theopropus elegans, Popa spurca, and Hymenopus coronatus. We quantified mantis spectral sensitivity to light, ranging from 350 to 650 nm wavelength, using electroretinography under both dark and chromatic adaptation. We find distinct spectral sensitivity peaks that suggest the presence of multiple photoreceptor types or varying expressions of visual pigments across the species studied. T. elegans and P. spurca exhibited potential trichromatic vision, with primary sensitivity peaks in green (515-525 nm), and secondary and tertiary peaks in ultraviolet (350-360 nm) and blue (441 nm and 416 nm). Conversely, H. coronatus displayed a simpler dichromatic pattern. This suggests praying mantises have the capacity for color vision, likely adapted to enhance camouflage and predatory efficiency in their environments.

Most humans have experienced regurgitation and vomiting (emesis) at some point in their lives. These behaviors are also commonly observed throughout the rest of the animal kingdom, serving various functions such as feeding, courtship, defense against predators, and protection from accidental toxin ingestion. Studying these behaviors offers valuable insights into the underlying gut-brain axis and presents opportunities to identify new therapeutic targets. However, detailed mechanistic studies on the molecular, genetic, and neural circuit basis of regurgitative behaviors have been hampered until recently due to the lack of suitable genetic model organisms capable of regurgitation. This review introduces researchers to the mechanisms of regurgitative behaviors, particularly those related to the gut-brain axis. We summarize these behaviors across different taxa, review current knowledge of their underlying mechanisms with a focus on gut-brain connections, and discuss related pathologies. Finally, we present recent findings from Drosophila models of regurgitation and emesis, and outline key questions that still require attention.

Species recognition is essential for reproductive isolation and plays a central role in the evolution of mating signals. In acoustically communicating species, temporal features of calls are critical for distinguishing conspecific from heterospecific signals. Anurans rely heavily on the precise timing of pulse trains for mate recognition. Females of Hyla chrysoscelis use the species-specific temporal structure of male advertisement (Adv) calls-specifically pulse rate (PR)-to select mates. For stimuli with the Adv call PR (40-60 pulses/s), females require at least ~ 6-7 pulses to approach a sound source, implicating interval-counting neurons (ICNs) in call recognition. To test this model and further investigate the neural basis of this temporal selectivity, we used behavioral and neurophysiological approaches. We lengthened interpulse intervals (IPIs) in pulse trains either at a single midpoint or in an alternating fashion while holding pulse number and, thus, stimulus energy constant. In phonotaxis assays, females showed sharply reduced responses when even one IPI was lengthened twofold or more, revealing high sensitivity to temporal irregularity. Single-unit in vivo extracellular recordings from the auditory midbrain revealed that ICNs exhibited a progressive decline in activity with increasing IPI length, closely mirroring behavioral trends. In contrast, long-interval neurons (LINs) responded more strongly to temporally irregular stimuli. These results support the hypothesis that ICNs mediate behavioral selectivity for conspecific Adv call temporal patterns, whereas LINs may contribute to processing other call types. Our study directly links a defined neuronal population to natural behavior, underscoring how midbrain temporal computations underlie species-specific recognition in Hyla chrysoscelis.

Atlantic salmon (Salmo salar) move from fresh- to seawater environments following a seasonally timed preparative transition called smoltification, which takes place under photoperiodic control in the freshwater environment. In masu salmon (Oncorhynchus masou), coordination of photoperiodic sexual maturation is proposed to involve in a fish-specific circumventricular organ, the saccus vasculosus (SV), through its intrinsic opsin-based light sensitivity, thyrotrophin secretion and modulation of deiodinase activity (TSH-DIO cascade). The saccus vasculosus is a highly vascularized structure located on the ventral side of the hypothalamus and its interface between the blood and cerebrospinal fluid also hints at a role in ionic balance of the cerebrospinal fluid (CSF). Both the potential photoperiodic and ionic functions of the SV led us to perform transcriptome analysis of the SV in smoltification in Atlantic salmon. Specifically, we compared transcriptomes of SVs collected from freshwater fish following exposure to an 8-week stimulated winter photoperiod followed by 8-week simulated summer photoperiod, or a 16-week simulated winter photoperiod control and from both photoperiod treatments after 24 h exposure to seawater. Our data show that SV response to seawater exposure is highly dependent on photoperiodic history and identifies ependymin as a major secretory output of the SV, consistent with a role in control of CSF composition. Conversely, we could not detect crucial elements of the opsin-TSH-DIO cascade suggesting that the photoperiodic history-dependence of the SV to seawater exposure is unlikely to stem from SV-intrinsic responses to photoperiod.

Research around the turn of the millennium showed that honeybees use the amount of optic flow during foraging flights to estimate the distance between a food source and the hive. Upon returning to the hive, they communicate this information to their nestmates by encoding distance into the duration of the waggle phase during the waggle dance. A celebrated figure in establishing the idea of an optic-flow-driven odometer is the Australian neuroethologist Mandyam Srinivasan. However, in 2024, news broke about alleged irregularities and scientific misconduct in ten of Srinivasan's articles, including a high-profile paper published in Science in 2000. To help readers navigate through the following five articles contributed by several key players in the honeybee odometer controversy, this editorial first provides some scientific background. It then outlines the major events that, beginning with the first allegations on PubPeer in 2020, culminated in 2024 with an escalation of accusations against Srinivasan in newspapers, magazines, and social media. Finally, the editorial summarizes Srinivasan's responses to these allegations and the corrective actions he has taken.

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.

The antennae are the primary olfactory organs of insects, though other appendages, such as mouthparts and the female ovipositor, can also detect odors. A prerequisite for the olfactory function of an appendage is the presence of sensilla with porous walls and the expression of chemosensory receptors by sensory neurons housed in these sensilla. In the tobacco hawkmoth, Manduca sexta, we demonstrate that the epiphysis, a small process on the tibia of the forelegs that is used to clean the antennae, is an olfactory organ. The epiphysis carries approximately 150 sensilla with wall pores, suggesting an olfactory function. Additionally, the epiphysis expresses a variety of chemosensory receptor genes. We identified the expression of ORCo, the obligate co-receptor of odorant receptors (ORs), as well as 54 tuning ORs. Moreover, the epiphysis expresses 22 ionotropic receptors (IRs), including the co-receptors IR8a, IR25a, and IR76b, and 33 gustatory receptors (GRs). Several of these IRs and GRs had not previously been found in the antennae or other appendages. Electrophysiological recordings from isolated epiphyses revealed responses to odorants from several chemical classes, host plant leaves, and the female pheromone gland. The strongest responses were elicited by acids and the amine pyrrolidine. Epiphysectomy did not affect courtship or foraging behavior; however, epiphysectomized females were less likely to reach a host plant than controls. Our study reveals the epiphysis of M. sexta to be a previously unknown olfactory appendage with a broad and partly unique chemosensory repertoire. Because the epiphysis is a constitutive feature of lepidopteran insects, its olfactory function may be present in most moths and butterflies.

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.

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.

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.

Butterflies have evolved a remarkable diversity in eye organization to support a range of vision-based behaviors including courtship, oviposition, and foraging. This diversity has been surveyed extensively across the butterfly phylogeny, but variation across closely related species remains less clear. We compared eye organization in Heliconius cydno, a clade of mimetic, Neotropical butterflies that have been studied in the context of wing coloration and courtship. Using a combination of eyeshine and opsin immunohistochemistry, we identified several sexually dimorphic features of eye organization where male eyes varied with species and female eyes did not. These features included the distribution of a red screening pigment across the eye, co-expression of the two UV opsins within single photoreceptors, and the relative distribution of UV and blue opsin expression in R1/R2 photoreceptors. Together, this suggests a shift in H. cydno males from an ancestor strongly biased towards the expanded Nymphalid mosaic characterized by blue and long wavelength opsin co-expression, red screening pigment, and green vs. red inter-photoreceptor opponency to one biased towards the basic mosaic consisting of UV-UV, Blue-Blue, and UV-Blue ommatidia. We hypothesize that this sex-limited variability may function to adapt these butterflies to sexually dimorphic behaviors like courtship and oviposition in the context of the natural light environment.

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.