Learning, memory, and brain plasticity are thought to play an important role in regulating behavioural roles in social insects, as workers perform different tasks as nurses, builders, foragers and defenders. However, it remains challenging to disentangle whether neural changes regulate behaviour or arise as a consequence of it. While cognition has been extensively studied, especially in honeybees, the variation of cognitive traits remains poorly understood in social wasps. Here, we investigated age-related changes in learning, memory and neuroanatomy in workers of the common wasp Vespula vulgaris. We developed a Y-maze to test differential conditioning and memory of wasps and later visualised the brains using a high-resolution micro-CT imaging. We found that younger individuals exhibited slower decision-making yet made more accurate decisions compared with older individuals, revealing a pronounced speed-accuracy trade-off. Short-term memory showed only a slight decline with age. Neuroanatomical image analyses revealed that, despite a reduction in overall brain volume, key major neuropils involved in sensory processing and learning, such as mushroom bodies, optic lobes and antennal lobes, increased in relative volume with age. These findings corroborate with studies in bees and provide novel insights into how ageing influences cognitive function and brain structure in wasps.

Since the 1950s, muscle contraction has been explained by the sliding filament and cross-bridge theories involving actin and myosin. However, these theories do not account for certain muscle properties, such as residual force enhancement (rFE). The sarcomeric protein titin has been proposed to contribute to active force and rFE, but its role remains unclear. A leading hypothesis suggests that titin binds to actin, thereby shortening its spring-like segment, with calcium regulating this interaction. We investigated the roles of calcium and cross-bridge formation in titin mechanics by measuring the length of titin's PEVK region in sarcomeres during (i) passive stretch, (ii) active stretch with cross-bridge inhibition (via BDM), and (iii) active isometric contraction. PEVK lengths were similar for passive and cross-bridge inhibited conditions but were longer for active contractions. Our results suggest that cross-bridge engagement, not calcium alone, modulates titin extensibility and passive force under physiological conditions.

Hydrostatic pressure in the marine environment increases linearly with depth, and organisms at 1000 m experience pressures 100 times greater than those at sea surface level. Previous work has examined the effects of pressure on neuron and nervous system activity in some organisms, as well as the various biochemical adaptations of deep-water species. However, the effects of pressure on other biological tissues are not well understood. In this study, we took the shallow-water jellyfish Aurelia aurita and exposed it to pressures of up to 30 MPa (equivalent to 3000 m depth). We observed behavioral and kinematic changes that are likely due to mechanical effects of hydrostatic pressure on the swimming muscles and bell mesoglea. The pulsation rate of the bell was found to correlate with hydrostatic pressure, although the effect was small relative to the variability between individuals (R2=0.124). Both the maximum contraction and relaxation rates of the bell were found to be significantly reduced at high pressure (30 MPa) relative to near-surface pressure (<1 MPa). The changes in pulse frequency and relaxation rate were both fully and immediately reversed upon release of pressure, but the change to contraction rate was not. Since bell contraction is controlled by muscle fibers and relaxation is controlled by elastic fibers in the mesoglea, the differential effects on contraction versus relaxation suggest that different tissues are affected differently by pressure. This opens the way for future work on how individual organisms can adapt to different environments.

The effect of global warming on rising aquatic temperatures is producing ever-steeper thermoclines. Fish encountering these sharp changes in water temperature might experience an acute-warming stress. Temperature is the most dominant environmental factor affecting heart function in fish, and without compensatory mechanisms as temperatures rise (e.g., higher heart rate), it could imperil cardiovascular performance. To enhance heart function during acute warming, fish release adrenaline to boost Ca2+ influx in heart cells (cardiomyocytes). However, the relationship between acute warming, elevated heart rate, adrenergic stimulation, and intracellular Ca2+ handling is not well understood at the cellular level. In this study, we investigated the interplay between these key functional drivers in isolated ventricular cardiomyocytes of rainbow trout, at either their acclimation temperature of 10°C or following acute warming (22°C). A subset of cardiomyocytes from each group was treated with either adrenaline, sarcoplasmic-reticulum (SR) inhibitors (that inhibit intracellular Ca2+ cycling via the SR), or both, while pacing frequency was simultaneously increased (simulating faster heart rate). Using epifluorescent microscopy, we measured intracellular Ca2+ transients (Δ[Ca2+]i) and Ca2+-cycling kinetics. Across all pacing frequencies, we found no differences in Δ[Ca2+]i between control (untreated) 10°C and 22°C cardiomyocytes, and that adrenaline had a positive inotropic effect at both temperatures, but was less effective at 22°C. SR inhibition had no effect on Δ[Ca2+]i, but was associated with a greater incidence of irregular Δ[Ca2+]i. Our data suggest that acute thermal stress can disrupt Ca2+-homeostatic mechanisms in trout cardiomyocytes, potentially disrupting whole-heart contractility as global temperatures rise.

Environmental signals exert influences not only on the current generation, but also extend to subsequent generations, even when these signals no longer persist. These transgenerational effects can be mediated through several mechanisms, including epigenetic inheritance and composition of the gut microbiome. In this study we investigated the contribution of the microbiome to diet-induced transgenerational effects on reproductive dormancy. Multiple strains of Drosophila simulans were subjected to a shift from sugar-rich to sugar-poor diet and the impact of this diet switch on dormancy was determined over multiple generations. Consistent with significant transgenerational effects, we observed a gradual reduction in dormancy incidence with an increasing number of generations exposed to the new, sugar-poor diet. Despite the variation in dormancy induced by the dietary shift, the microbiome composition remained largely stable. Consequently, we conclude that these transgenerational effects are not determined by changes in the bacterial microbiome composition.

This study investigated how unsteady flow conditions influence the swimming physiology and energetic performance of Chinook salmon using co-implanted heart rate (HR) and acceleration (AC) sensors. Fish were monitored for HR, AC, and overall dynamic body acceleration (ODBA) in two experimental settings: (1) controlled swimming at increasing speeds (0.15-0.90 m s⁻¹) in a swim-tunnel under steady and unsteady flow, and (2) free-swimming sentinel fish in tanks under steady and subsequent unsteady flow for two weeks each. In experiment 1, HR remained consistently high (81-84 bpm) across all speeds under both flow conditions, suggesting limited capacity to further elevate cardiac output. MO2 increased from 213±10 to 307±16 and from 225±12 to 330±17 mg kg-1 h-1 under steady and unsteady flow, respectively. AC and ODBA increased linearly with speed and were positively correlated under both flow conditions. In experiment 2, circadian patterns were evident in HR, AC, and ODBA of the free-swimming fish. Fish exhibited higher daytime and nighttime HR and AC under unsteady flow compared to steady flow conditions, while ODBA remained similar. Regression models based on swim-tunnel data accurately predicted AC and ODBA in free-swimming fish, indicating consistent relationships between swimming speed and acceleration dynamics. The higher HR and AC of free-swimming fish under unsteady conditions indicated a 3-5% increased energetic investment. Overall, this study provides insight into how dynamic flow environments shape the physiological responses of Chinook salmon, informing predictions of fish performance in offshore aquaculture systems.

Incubation temperatures within sea turtle nests are governed by complex abiotic and biotic interactions. Established methods for estimating these temperatures include deploying temperature loggers at standard nest depths or using models to predict sand temperature. While these approaches capture abiotic drivers of incubation temperatures, they often fail to fully account for biotic factors, including the heat produced by the metabolism of embryos, despite its potential impact on hatchling development and mortality. Here, we applied finite element analysis to predict incubation temperatures for all embryos in five flatback sea turtle (Natator depressus) nests. To parameterise the models, we measured clutch size, nest depth, temperatures at several locations around nests, and the physical properties of beach sand, including density and moisture. Next, we simulated within-nest temperatures with an energy balance model that accounted for metabolic heat by applying an hourly heat flux, based on modelled embryonic metabolic rates, to each egg. Each model was validated by comparing predicted temperatures with observed temperatures at the base, centre and top of each clutch. On average, finite element models achieved good accuracy to within 0.4°C of observed data (mean error over the entire incubation period). By incorporating individual clutch size, nest depth and the metabolic contributions of embryos, our approach enhances the realism of temperature estimates for predicting the embryonic development of sea turtles, which is of increasing importance under rapid climate change.

Supervised machine learning is commonly used to classify fine-scale behaviours from animal-borne accelerometers, assigning new data to predefined behaviour categories seen during training. These models cannot recognise novel behaviours as "unknown", however, and, when exposed to new behaviours, will continue to overpredict the known classes. This issue - known as Open-Set Recognition - is an inevitable, but underexplored, limitation in accelerometer-based behaviour classification. Here, we describe the problem and assess four solutions: (1) a multiclass model with an "other" category, (2) threshold-based models, (3) one-class models, and (4) binary one-vs-all models. We show that traditional multiclass models produce high false-positive rates when exposed to behaviours not present during training. We instead suggest the implementation of binary one-vs-all models as a more conservative method, particularly in cases where a single, or limited set of behaviours are of interest. Awareness of this challenge will enhance recognition of often unreported uncertainty in real-world applications.

Southern right whales (Eubalaena australis, SRWs) are well adapted to cold waters due to their large body size and thick blubber. Each year, they migrate from high-latitude feeding grounds to warmer breeding grounds where they give birth. To assess thermal benefits of this migration, we modelled the effects of body size, condition, and water temperature on heat loss. Using unmanned aerial vehicle photogrammetry at the Península Valdés (PV) calving ground in Argentina, we measured body length, volume, condition, and surface area of living SRWs. Blubber thickness was predicted from a blubber-mass model and validated using necropsy/catch data. Sensible heat loss was estimated using a model incorporating blubber thermal conductivity and body temperature, while respiratory heat loss was based on respiration rate and tidal volume models. We compared heat loss in PV to South Georgia/Georgia del Sur (SG/GS), a key feeding ground. Body size had a strong positive effect on both heat loss types, but mass-specific loss decreased as surface-area-to-volume ratio declined. Increased body condition reduced sensible heat loss. Migration from SG/GS to PV reduced calf heat loss by 26% during early lactation. However, total heat loss remained low relative to field metabolic rate (FMR), indicating limited thermoenergetic benefit from migration. Only at poor body condition (<-0.35) did heat loss exceed FMR, threatening survival. Notably, gull-inflicted lesions significantly increased heat loss in small and poorly conditioned calves, but had no effect on larger or better-conditioned calves. These findings highlight body condition as a key regulator of heat loss in baleen whales.

Weakly electric fish rely on electrosensory, visual, and mechanosensory (lateral-line) cues to guide behavior in flowing water, yet the effects of ambient currents on multisensory tracking and active sensing remain poorly understood. We tested the weakly electric knifefish Apteronotus albifrons (N=4) tracking a moving refuge in a recirculating flow tunnel while systematically varying flow speed (0-16 cm s-1), illumination (light vs. dark), and refuge structure (windowed vs. nonwindowed). Tracking performance was quantified with time- and frequency-domain measures (root-mean-square error; gain-phase analyses), and active sensing as movement power outside stimulus frequencies (mean active sensing power, MASP). Increasing flow degraded tracking: relative to still water, RMSE rose by ∼46% at 16 cm s-1. Deficits were largest in darkness and with the windowed refuge, and were concentrated at low stimulus frequencies. Under higher flows, fish showed a trend toward increased off-frequency movement power (by ∼33%), consistent with compensatory active sensing to sustain sensory acquisition. The effects were nonlinear and context dependent. This pattern indicates that increasing hydrodynamic noise may drive dynamic reweighting among visual, electrosensory, and mechanosensory inputs. Collectively, our data indicate that ambient flow degrades low-frequency tracking and may elicit compensatory active sensing in A. albifrons, extending recent demonstrations of context-dependent sensing and control switches in this species and bridging rheotaxis with electrosensory refuge tracking.

The ability to enhance heat production in response to prolonged cold exposure (cold acclimation capacity) is a key physiological adaptation in some endotherms, such as eutherian mammals, owing to a specialized mechanism of adaptive non-shivering thermogenesis in brown adipose tissue, mediated by uncoupling protein 1, which seems to be absent in marsupials and birds. Phenotypically, it is unclear whether these endotherms lack cold acclimation capacity or whether they have other facultative heat production mechanisms. To test for differences in thermal acclimation capacity, we analyzed published studies measuring maximum metabolic rates following cold acclimation. Using generalized linear models, phylogenetic generalized least squares and meta-analyses, we compared placentals, marsupials and birds. The results consistently indicated that placental mammals exhibit significantly greater cold acclimation capacity than marsupials and birds. Meta-analysis revealed maximum rate of oxygen consumption responses as being 101.8% higher in placentals than those in birds and 301.2% higher than those in marsupials. Our findings suggesting superior thermogenic plasticity in placental mammals reflect unique evolutionary adaptations, permitting these animals to thrive in seasonally cold environments, which is especially important when migration capacity is limited. Birds, however, with lesser migratory restrictions, would have prioritized the insulating capacity of feathers as an evolutionary solution to the cold. Marsupials, without the innovation of adaptive thermogenesis, would have a geographical distribution restricted to non-extreme areas.

One of the great puzzles in biology is to understand the mechanisms underlying animal regeneration. Most recent efforts have used developmental and informatics approaches to understand how regenerated structures are formed, framing regeneration as a developmental outcome. However, regeneration is a complex process that also involves dynamic physiological mechanisms that support and fuel the rebuilding of lost structures. To develop a full understanding of regeneration, including how it relates to the ecology and evolution of organisms, it is essential to understand regeneration physiology. Despite the importance of physiological processes for regeneration, studies of regeneration focused on energetics, metabolism and environmental effects are scarce and have not been synthesized. This Review discusses the current understanding of regeneration physiology, focusing specifically on data from invertebrate animals where such information is especially dispersed and in need of synthesis. Considering data from diverse animal phyla, we review evidence for the consumption of different nutritional substrates during regeneration, summarize how aerobic and anaerobic metabolism appear to be broadly important to regeneration across animal phyla, and discuss how environmental and biotic factors can affect regeneration outcomes. We also introduce the concept of the 'physiological regeneration niche', describing the abiotic and biotic parameters where regeneration is possible, to expand consideration of regeneration in an ecological context. Significant gaps remain in understanding the physiological processes that underlie invertebrate regeneration, and we highlight some of these, including the need for broader taxonomic sampling, assessments of anaerobic metabolism during regeneration, investigations of multiple stressor effects on regeneration and comparisons between regenerators and non-regenerators.

The honeybee waggle dance communicates a flight vector to a food source, but it is challenging to isolate how precisely dancers and recruits can navigate using this vector information independently of environmental cues. We introduce an enforced-detour paradigm, using tunnels, to quantify the initial flight vectors expressed by experienced foragers and new recruits en route to the food. Upon exiting the detour, bees exhibit immediate corrective turns consistent with using path integration to fly towards the food's virtual location. While the populations' flight bearings after the turn are correctly centred on the food, the bearings of individuals are considerably scattered around it. We further show that recruits' bearings can be predicted by observing their mechanical sensory experiences during dance following. Our findings suggest that the communicated or recalled vector can be combined with path integration to take corrective shortcuts, but also that the vector provides an approximate location rather than pinpoint accuracy.

Many studies have demonstrated that anthropogenic noise affects animals' auditory perception of salient stimuli. Few have tested whether these effects are different from those experienced in nature. We tested the ability of female field crickets, Teleogryllus oceanicus, to phonotactically locate a speaker playing conspecific male song in four acoustic backgrounds: silence, road noise, river noise, and heterospecific song. Crickets approaching conspecific song paused more frequently in river noise and heterospecific song treatments compared to silence or road noise. We also recorded auditory interneuron (AN1 and AN2) activity under the first three acoustic background treatments to construct and compare treatment-specific audiograms and interneuron response to conspecific song. We found little difference in activity, other than that AN2 thresholds for 6 kHz sounds (the tested frequency closest to male song) were highest in river noise, while heterospecific song increased baseline AN2 activity and reduced AN2 activity to conspecific song onset. Our results suggest road noise is not necessarily a greater disturbance than river noise.

Although some migratory animals can derive directional (compass) and positional (map) information from Earth's magnetic field, the underlying mechanisms of magnetic sensing have remained enigmatic. One hypothesis proposes that crystals of the mineral magnetite (Fe3O4) function in magnetoreception, a concept bolstered by findings that brief, strong magnetic pulses capable of reversing the magnetic dipole moment of magnetite affect magnetic orientation responses of several animals. Disentangling whether such pulses affected an animal's magnetic compass sense or magnetic map sense, however, has often been difficult. Here, we investigated the effect of a magnetic pulse on the magnetic map sense of loggerhead sea turtles (Caretta caretta) using an established conditioning assay that requires turtles to use magnetic map information but not their magnetic compass. We report that a magnetic pulse disrupted turtle responses, consistent with the interpretation that the magnetic map sense of turtles is based at least partly on magnetite-based magnetoreceptors.

Much of the research into white-nose disease has focused on the hibernation period, while the pathogenic fungus Pseudogymnoascus destructans is actively infecting the bat host. Previous research has found large differences between the susceptible North American Myotis lucifugus and the tolerant European Myotis myotis, suggestive of immunopathology in the former, and a beneficial lack of strong response in the latter. Here we examine gene expression in these species during both the late-hibernation period, and a month after emergence from hibernation, during healing from infection. We utilised paired sampling, collecting wing tissue that was positive and negative for fungal infection fluorescence, to examine changes in whole-transcriptome gene expression that were local to sites of infection at two timepoints: pre-emergence and 30 days post-emergence from hibernation. Positive samples were contrasted between the two timepoints to examine longitudinal changes. During the pre-emergence period, local inflammatory responses are observed in both M. myotis and M. lucifugus. Immune responses between the tolerant and susceptible species are dissimilar, favouring Th1 and Th17 cytokine responses respectively. This lends weight to immunopathology as a contributing factor to mortality in M. lucifugus. Continual immune responses may not only contribute to immunopathology and host mortality, but may also have important carry-over effects on reproduction and subsequent pre-winter fattening, affecting population viability over a longer period of time than previously considered.

Here we test whether food availability limits phenotypic plasticity in thermal tolerance in the amphipod Echinogammarus marinus. We shifted specimens from 10°C to an acclimation temperature of 20°C, and kept them there for different durations with and without food before measuring the time to immobilization at 30°C. Our results show that thermal tolerance increases with acclimation duration, but this response was about two times more pronounced in fed than in unfed individuals. We also decomposed the plastic response into a rate (how fast the trait changes) and capacity component (by how much it changes). This showed that the overall effect of food treatment on the temporal dynamics of thermal tolerance was primarily driven by the effect on capacity. We conclude that laboratory derived thermal tolerance data from experiments where ecological conditions are otherwise optimal may provide overly optimistic estimates of how well organisms deal with extreme events through phenotypic plasticity.

Infant mammals must suckle in order to acquire food. Many factors, including the design of a nipple, impact suckling, and thus can alter feeding performance. For example, feeding on a bottle nipple that has ducts embedded in silicone requires infants to generate suction to acquire milk, whereas a hollow bottle nipple allows infants to express milk via nipple compression. Furthermore, the design of a nipple impacts milk flow, and likely changes the relationships between suction generation, tongue kinematics and milk flow. In this experiment, we designed two ducted bottle nipples with similar properties and flow rates but with different branching patterns (a nipple with multi-level branching ducts and a nipple with a single central channel), and compared feeding performance with a hollow, cisternic nipple. We also experimentally calculated milk flow using a venturimeter attached to the single ducted nipple, while synchronously recording high-speed biplanar videofluoroscopy and intraoral pressure generation in infant pigs, a validated animal model. We found no significant differences between the ducted nipple types, but infants showed greater suction generation, different tongue kinematics and smaller bolus sizes when feeding from the ducted nipples as compared with a hollow, cisternic nipple. We calculated milk flow and volume per suck using the venturimeter, and saw correlations between milk flow rate and both middle tongue translation and intraoral suction generation. Overall, these data demonstrate that nipple design has a profound impact on the relationship between infant feeding physiology and milk flow.

Many animals form behavioral collectives, and optimal interaction strategies often differ across social contexts. Sensory scenes generated by many interacting conspecifics are complex. Thus, maintaining socially-calibrated responses requires individuals to distill key features from conspecific scenes to guide continued adjustments to social fluctuations. Túngara frogs produce mating calls in choruses varying in size, and interaction patterns differ across social environments; rivals alternate their calls in smaller choruses, but increasingly overlap one another's calls in a stereotyped fashion as chorus size increases. We used automated playback to investigate the cues guiding this socially-mediated shift in interaction modes. We played conspecific stimulus calls to males at various delays relative to their own calls, preceded by various acoustic motifs that mimicked conspecific stimulation patterns males will hear in different social environments. Males almost never overlapped isolated stimulus calls at any delays. However, their probabilities of overlapping stimulus calls increased markedly when stimulus calls were preceded by motifs characteristic of larger choruses, i.e. those exhibiting intense conspecific stimulation patterns. Furthermore, the escalatory effects of motifs became increasingly pronounced as motif/stimulus combinations were played at later delays. Thus, interaction strategies are calibrated to current social dynamics each call cycle in response to a multifaceted cue that incorporates both the nature of conspecific stimulation experienced and how the timing of this stimulation interacts with endogenous responsiveness rhythms. Our results highlight that inactive phases within behavioral rhythms provide repeated opportunities to sample current social dynamics, allowing response patterns to be continually calibrated to social fluctuations in behavioral collectives.

Positive phototaxis in diurnal bees is modulated by wavelength and intensity of light. Unlike diurnal bees, nocturnal bees like Megalopta aegis forage exclusively during twilight, when light intensity drops rapidly and irradiance peaks in the blue spectrum. How light parameters influence phototaxis in these nocturnal bees remains unclear. We evaluated the phototactic responses of M. aegis in a dark circular arena using UV, blue, and green monochromatic lights presented at six absolute intensities. Contrary to diurnal bees, M. aegis was not always attracted to light. When attracted, they showed stronger attraction to UV than to blue or green. Paths toward UV were shorter, faster, and straighter, suggesting a greater involvement of UV-photoreceptors in this phototactic behaviour. Compared to honeybees tested in similar experimental setups, M. aegis exhibited slower but more directed paths. These results align with their highly light-sensitive eyes, which trade-off temporal resolution for improved reliability in dim light.

The intertidal zone experiences significant fluctuations in temperature and pH, posing significant challenges to marine organisms. Perinereis aibuhitensis, a eurythermal and euryhaline polychaete inhabiting estuaries, where pH is often lower than in the open ocean and further reduced within sediments, has likely evolved robust adaptations to such stresses. We investigated its behavioral, physiological, and metabolic responses under combined temperature (15°C, 20°C, 25°C) and seawater acidification (pH 5.5, 6.7, 8.0) conditions. P. aibuhitensis exhibited stable behavioral performance and metabolic homeostasis under control conditions (20°C, pH 8.0). It maintained burrowing activity and activated physiological and metabolic regulation at pH 6.7. However, its motion significantly declined with failed behavioral regulation under pH 5.5: radial undulation duration decreased by 97.63% and pumping volume by 97.97%. Energy was reallocated toward antioxidant defense and maintenance of basic physiological functions, reflected in downregulation of the γ-aminobutyric acid (GABA) metabolic pathway alongside upregulation of ABC transporter and arachidonic acid metabolism. At 25°C, combined warming and acidification disrupted energy allocation under pH 5.5. This disruption was accompanied by enhanced motion, which further constrained energy allocation, leading to significant oxidative damage (MDA content increased by 94.54%) and concurrently impairing tryptophan metabolism, glycerophospholipid metabolism, and ABC transporter function, with the entire cascade ultimately collapsing its adaptive mechanisms. This demonstrates that severe acidification, especially under warming, compromises bioturbation and metabolic stability in P. aibuhitensis, with potential negative impacts on polychaete communities and their vital ecological functions in intertidal ecosystems. Our findings provide critical insights for predicting climate change impacts on marine infauna.