Journal of Experimental Biology最新文献

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 examined gene expression in these species both during 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 time points: pre-emergence and 30 days post-emergence from hibernation. Positive samples were contrasted between the two time points to examine longitudinal changes. During the pre-emergence period, local inflammatory responses were observed in both M. myotis and M. lucifugus. Immune responses between the tolerant and susceptible species were 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 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.

Females communicate non-genetic information about the environment to their developing offspring to generate potentially adaptive phenotypic variation. For example, birds allocate steroid hormones to their egg yolks in response to social stimuli and these hormones can induce long-lasting changes to offspring physiology and behavior. However, little work has explored how multiple yolk steroids respond to social challenges, despite their shared biosynthetic pathway, or how they impact early development. Here, we conducted simulated territorial intrusions to identify socially responsive yolk steroids using liquid chromatography with tandem mass spectroscopy (LC-MS-MS) and explored their relationship with gene expression patterns in extra-embryonic membranes during the earliest stages of embryonic development in house sparrows (Passer domesticus). We also characterized how yolk hormones changed across development, from embryonic day 0 (ED0) to ED5. We found that yolk hormone concentrations largely declined with embryonic development, but at ED0 multiple hormones along the androgenic pathway were elevated in response to the number of territorial intrusions a female experienced, with yolk testosterone and progesterone showing the strongest responses. At ED3, these socially responsive yolk hormones were related to gene expression in extra-embryonic membranes linked to key developmental processes, such as growth and immune function. These data highlight a critical early window during which yolk hormones may impact offspring traits through changes in extra-embryonic gene expression.

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-computed tomography 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 analysis 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.

In aquatic species such as fish, the integumentary system, comprising skin and scales, serves as a crucial defense against puncture from high-velocity impacts. While previous studies have focused on quasistatic puncture behavior and constrained targets, here we investigated the less-studied dynamic puncture behavior in both constrained and unconstrained fish integument samples. We used cone snails as a model organism, which utilize a ballistic radular tooth to penetrate and paralyze prey. Our dynamic puncture experiments demonstrate that fish integument effectively mitigates damage from predatory mechanisms at biologically relevant speeds. While higher velocities typically result in deeper penetration, puncture performance is significantly reduced at lower speeds in unconstrained targets. These findings reveal the protective function and biomechanical efficiency of fish integument, with high puncture resistance attributed to material properties, momentum transfer and mobility. Our results highlight the adaptive strategies of cone snails in overcoming these defenses with greater velocity and energy.

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-versus-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-versus-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.

Understanding the neural basis of animal behaviour requires a thorough description of the associated sensory inputs. This is especially important when behaviour actively shapes incoming sensory information. Weakly electric fish use perturbations in a self-generated electric field as a basis for an electric sense, and these field perturbations are encoded by electroreceptors distributed over their bodies. Thus, swimming movements and body pose shape not only the field but also the orientation of the receptor array. Previous modelling in this context has focused primarily on the so-called electric image in stationary fish and has not addressed how natural electrosensory inputs are generated in freely swimming fish. Here, we present fish2eod, an open-source finite-element-based modelling framework that describes the dynamics of electrosensory inputs during natural behaviours, including social interactions, in complex environments.

Freshwater ecosystems play a critical role in supporting biodiversity and providing essential environmental services. However, these ecosystems are increasingly threatened by human activities, including habitat loss, pollution and climate change. Traditional assessment methods focus on water properties, but biomonitoring approaches, particularly those examining behaviour and cognition, provide valuable insights into the ecological effects of pollutants. This study examines the effects of three common pollutants (glyphosate, atrazine and paracetamol) on the cognitive abilities of Aedes aegypti mosquito larvae, a vector for several diseases. We used an automated bioassay to study habituation learning and the effects of the three pollutants alone or in combination, at sub-lethal doses ranging from field-realistic to commercially recommended levels. Our results show that the three compounds modulate individual spontaneous activity and impair habituation and memory retention. These changes may alter the perception or the behavioural response of mosquito larvae to signals of their environment as indicating the presence of conspecifics or predators, and suggest that other organisms living in freshwater ecosystems may also be affected. Incorporating behavioural and cognitive assessments in ecotoxicological studies provides a more comprehensive understanding of the ecological effects of pollutants, which is needed to address economic challenges in fragile ecosystems.

Southern right whales (Eubalaena australis; SRWs) are well adapted to cold waters because of 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 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, whereas respiratory heat loss was based on respiration rate and tidal volume models. We compared heat loss in Península Valdés with that in South Georgia/Georgia del Sur (SG/GS), a key feeding ground. Body size had a strong positive effect on both heat loss values, but mass-specific loss decreased as surface-area-to-volume ratio declined. Increased body condition reduced sensible heat loss. Migration from SG/GS to Península Valdés 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.

Positive phototaxis in diurnal bees is modulated by the wavelength and intensity of light. Unlike diurnal bees, nocturnal bees such as 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. In contrast 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 with 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.