Journal of Experimental Biology最新文献

Echolocating big brown bats hunt insects flying along unpredictable paths in front of vegetation. We conducted three psychophysical experiments to investigate how these bats alter their spatial attention when localizing virtual target echoes appearing unpredictably in azimuth and against weak physical clutter. Four bats were trained to detect virtual echoes presented from a 120° azimuthal array of six loudspeakers. Within a single trial, echoes could remain in the same position or shift unpredictably to a new one. The bats performed well in stationary trials but were less accurate when targets shifted more peripherally and contralaterally to the original azimuth. They aimed their sonar beams accurately at targets appearing centrally; they were less precise but faster when localizing targets in the periphery, maintaining a more central acoustic gaze with only momentary peripheral shifts. When localizing a shifted target, bats reduced the interpulse intervals between broadcasts and emitted proportionally more sonar sound groups, suggesting increased perceived task difficulty. Weak clutter located closely behind the virtual target reduced accuracy in localizing target shifts, affected the speed of beam aim adjustment, and was associated with an increase in broadcast duration. Interpulse intervals and sonar sound groups were not strongly affected by clutter. Behavioral differences between bats showed the impact of individual problem-solving strategies. These findings demonstrate that the distribution of spatial attention is biased towards the center of the ensonified field of view and is influenced by weak background clutter.

A honey bee colony's well-being is its ability to nurture larvae into healthy adults. Understanding how nutrition supports brood rearing is crucial for developing diets that could aid against environmental threats. Nutritional research on whole-colony brood development has been historically challenging because of difficulties documenting the diet's impact on brood production over time. We describe a novel semi-field method to study the influence of nutrition on brood rearing using standardised small colonies formed de novo (ca. 1500 nurse-age bees and a queen) housed in adapted mating-nucs, placed inside an enclosure and limited to feeding on chemically defined diets. Complete assessments were conducted every 15 days, assisted by a bespoke device to photograph every frame to measure cell contents. A novel metric describes the number of bees generated per gram of diet consumed, measuring the impact of nutrition on brood rearing and overall colony size.

The fast axial muscles of larval bony fish power rapid escape responses, crucial for survival under high predation pressure. In adult and juvenile teleosts, these muscles follow a pseudo-helical pattern, while those of larval zebrafish (Danio rerio) exhibit a helical arrangement. However, its developmental time line remains unclear. We analysed muscle-fibre orientation in genetically modified zebrafish from 2 to 13 days post-fertilization (dpf) using 3D fluorescence confocal microscopy. Fibre angles were quantified relative to the notochord, and a model of circular, concentric helices was fitted to assess helical trajectories across development. Our results show that a helical pattern is already present at 2 dpf, tapering towards the tail. The pattern remains stable over the first 11 days post-hatching, with decreasing projection angle variation toward the tail, particularly in younger larvae. Across developmental stages, helix centres align at corresponding normalized positions along the notochord. This study highlights the early presence of a helical fibre arrangement in larval fish, with no evidence of pseudo-helical deviations up to 13 dpf.

The common big-eared bat (Micronycteris microtis) gleans its prey directly from plant surfaces. Previous experiments have shown that this bat exploits the specular reflection effect to discriminate between occupied and empty leaves. Using this effect requires the bat to position itself such that it can ensonify the leaves at sharp angles. If the bat can perceive the orientation and position of individual leaves, it could position itself to take advantage of the specular reflection. However, this would be a highly inefficient foraging strategy. The bat would first have to inspect each leaf to determine its position and orientation. Given that, under natural conditions, the vast majority of leaves do not feature prey, this would require the bat to spend most of its time collecting information on empty leaves. Here, we propose a strategy that allows a bat to exploit the specular reflection effect without inferring the position and orientation of individual leaves. We implement this strategy on a robotic arm equipped with a sonar head. The robot is tasked with finding a 3D-printed dragonfly on one of a set of artificial leaves. The robot follows an echo amplitude gradient and abandons this search whenever the echoes become too weak. Importantly, the robot does not actively find or locate individual leaves. We show that the proposed sensorimotor model can exploit the specular reflection effect to efficiently and effectively locate prey. Our results increase the plausibility of M. microtis using the specular reflection effect under natural conditions.

Cardiac mitochondria in fish are remarkably plastic, with the capacity to change in volume and density, membrane composition and fluidity, aerobic capacity and reactive oxygen species production. This flexibility allows the highly aerobic fish heart to cope with temperature variations, thus enhancing animal fitness and survival, a feature that is particularly important for species living under narrow thermal regimes. This Review explores the remodelling of fish cardiac mitochondria in response to temperature variation, focusing on their role in supporting heart function. It highlights the mechanisms underlying these adaptations, the impact of acute and chronic thermal stress, and specific responses to environmental challenges with reference to the pressure imposed by rapid and extreme thermal events. The unique adaptations of Antarctic fish to cold environments are used to exemplify extreme evolutionary events, with distinct mitochondrial morpho-functional features facilitating survival under frigid conditions. Throughout the Review, attention is given to mitochondrial membrane dynamics, oxidative phosphorylation and the production of reactive oxygen species. Despite growing research effort, species-specific phenotypic and genotypic mechanisms that sustain the response of fish cardiac mitochondria to fluctuating temperatures are not fully understood. Further research in this area is important not only in terms of basic knowledge but also to understand how global climate change shapes the energetics of fish cardiac performance, influencing animal resilience.

Power required to fly for a bird generally follows a U-shaped function of airspeed, with higher cost at both low and high speeds. Because power required increases with body mass faster than power available from flight muscles, larger birds may experience restricted flight speed ranges and climbing capabilities. Previous studies found limited flight performance in cormorants. Adapted for both flight and sub-surface swimming, they trade off larger flight muscles for powerful leg muscles used for diving. Our study tested whether the flight performance of greater cormorants is constrained by measuring airspeed under various seasonal and wind conditions. If flight muscles severely limit the range of flight speeds, cormorants would not be able to adopt ecologically relevant speeds between seasons and not increase speed in headwinds to minimize cost of transport. Results suggest that cormorants can achieve airspeeds beyond minimum power speed, selecting speeds near maximum range during autumn migration and exceeding this range on spring migration and during foraging flights. However, expected speed adjustments to headwinds were inconsistent, with some situations lacking the anticipated responses. The cormorants demonstrated partial wind drift compensation by adjusting flight headings along coastlines, though airspeed adjustments were not always observed. Although greater cormorants appear capable of reaching ecologically relevant speeds in many contexts, the overall scope of their flight speeds remains relatively narrow compared with smaller bird species. These findings indicate that greater cormorants have muscle power for adaptive behaviour in some cases, despite the influence of physiological constraints on their flight performance.

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.