Journal of Experimental Biology最新文献

Hummingbirds possess many distinct traits that make them stand out among birds. Among those features is the use of high-frequency vocalizations as part of the vocal repertoires of some species. These frequencies are much higher than what most birds are known to produce and hear. However, the mechanisms for the production and perception of these vocalizations are yet to be elucidated. This Review summarizes what we have learned about high-frequency vocalizations in hummingbirds in the past decade, as well as potential mechanistic explanations for this behavior. We aimed to compile a broad understanding of the potential proximate and ultimate mechanisms for such extended vocal production and auditory perception, emphasizing the need for comparative studies. By understanding how hummingbirds have adapted to communicate in complex acoustic environments, we may be able to predict how a rapidly changing environment will influence species with extraordinary sensory capabilities compared with other closely related taxa.

Catecholamines may react with other molecules to produce catecholamine derivatives. For example, nitric oxide may induce nitration of dopamine to form 6-nitrodopamine (6-ND). The endogenous production of such a novel catecholamine has been demonstrated in the mammalian and reptilian cardiovascular system, and in vitro studies demonstrate that 6-ND relaxes pre-contracted aortic rings, and acts as a potent chronotropic agent. So far, however, the in vivo effects of 6-ND remain to be characterised in whole organisms. Using South American rattlesnakes (Crotalus durissus), we measured the endogenous production of 6-ND and other catecholamine derivatives in different tissues of the cardiovascular system and the intercostal muscle. We also used myography to measure the vascular reactivity of the mesenteric artery to 6-ND, and we utilised anaesthetised individuals to measure haemodynamic responses to bolus injections of 6-ND (1 μmol kg-1). Except for blood plasma, 6-ND was detected in all tissues studied, and the addition of l-NAME, a blocker of nitric oxide synthesis, did not alter the production of 6-ND, indicating there are alternative biosynthetic pathways. The isolated mesenteric artery contracted in the presence of adrenaline, dopamine, noradrenaline and 6-ND. We also observed a potentiation of the noradrenergic stimulation in the presence of 6-ND. Finally, injection of 6-ND elicited a small but significant reduction in the mesenteric conductance. It is likely that 6-ND per se exerts small effects on overall haemodynamics, but synergises with noradrenaline and possibly other catecholamines to enhance cardiovascular regulation.

Animals have evolved multiple sensory systems that can acquire environmental information guiding their behaviour, allowing them to adapt physiological parameters to current conditions. However, over the past century, anthropogenic changes have increasingly made information on environmental conditions less reliable, by introducing novel elements (such as synthetic chemicals or artificial light), by altering environmental parameters such as temperature, and by introducing fluctuations. Animals using multimodal information perceived through multiple senses may be more resilient to changes, as they can adjust their sensory strategy, giving more weight to information channels that are less disturbed than others. In this Commentary, we propose that to better understand how animals are affected by disturbed access to sensory information that is caused by anthropogenic influences, sensory biologists need to study all developmental stages of a wide range of species, and include entire ecosystems in their thinking. Comparative, interdisciplinary studies will be increasingly important if we are to understand and mitigate the sensory consequences of anthropogenic changes for animals.

The ability to detect carbon dioxide and water vapor is essential for insect survival. Insects possess specialized receptors and anatomical structures that confer remarkable sensitivity to these environmental factors. As both CO2 and humidity are prominent greenhouse gases, understanding how insects sense and respond to these variables is crucial given global fluctuations in climate. This Review consolidates current insights into the molecular and neural mechanisms underlying CO2 and humidity detection in insects, with a focus on their roles in respiration, water balance and osmoregulation. It highlights case studies of context-dependent functions of these sensory systems in insect-plant interactions and host-seeking behaviors of blood-feeding species. At broader spatial scales, the roles of CO2 and humidity detection are explored for orientation and long-distance navigation behaviors. With growing concerns for declining insect populations, changes to plant-pollinator networks and range expansion of disease vectors, advancing research across biological levels is essential. Finally, the breakthroughs in single-cell and long-read sequencing technologies coupled with sophisticated behavioral tools should be leveraged to fill phylogenetic gaps, explore drivers of specialization, identify vulnerable populations and uncover mechanisms of resilience.

The swallowtail butterfly Papilio xuthus is a model species in insect vision science, thanks to extensive studies over the past few decades. P. xuthus adaptively uses visual cues such as color, brightness, polarization and motion in various steps of flower-foraging behavior. We have explored these visual functions from both perceptual and physiological perspectives. This Review aims to summarize these studies by focusing on color vision as a prominent ability in foraging P. xuthus and on wide-field motion vision as a more-universal visual modality in insects. The compound eyes of P. xuthus consist of three types of ommatidia, each with a different combination of spectral receptor classes: sensitive to ultraviolet (UV), violet (V), blue (B), green (G), red (R) and broadband (BB) wavelength regions. Connectome analysis of the first optic ganglion, the lamina, reveals interphotoreceptor interaction causing spectral opponency and spectral integration in the second-order lamina monopolar cells (LMCs). These characteristics should be crucial in the initial processing underlying the acute color discrimination ability of tetrachromatic color vision based on UV, B, G and R receptors, as well as motion vision involving G, R and BB receptors. In addition, we have revealed that the spectral properties of interneurons connecting the optic lobe and the central brain well explain the behavioral properties of P. xuthus. By discussing the visual system of P. xuthus butterflies in conjunction with knowledge from honeybees, flies and other lepidopteran insects, we will provide valuable insights into the evolution of insect visual systems.

Hypoxia and hypercapnia often accompany seawater warming and interactively alter marine ectotherm performance, potentially threatening their populations. To detail mechanistic responses, we investigated whole-animal physiology alongside cellular homeostasis in a species expected to be relatively robust to their impacts, the oyster Ostrea edulis. Acute warming alone and combined with hypercapnia and hypoxia (deadly trio, DT) started at 18°C, increasing stepwise by 2°C per 48 h until critical temperature was reached (34°C). Death of oysters started at a lower temperature under DT than under acute warming alone, but rates equalized by 34°C. Hemolymph PO2 in DT-exposed oysters was 29% lower at 18°C, but by 34°C, was only slightly lower than that in oysters subjected to acute warming alone. In both groups, resting metabolic rate (RMR) and heart rate rose with warming. Hemolymph PO2 was stable until 26°C, whence it declined. DT elicited a higher heart rate, which began to fall after ∼32°C, whereas heart rate in oysters subjected to acute warming continued rising. Relative increases in branchial metabolite levels of alanine and fumarate, profiled via 1H-NMR spectroscopy, indicated greater contributions of anaerobic metabolism in DT-exposed oysters. Gill tissue showed higher levels of the mitochondrial stabilizer sirtuin-5 (SIRT5) alongside higher antioxidative capacity under DT compared with acute warming, before declining at temperatures beyond 30°C. Muscle intracellular pH, gill heat shock protein 70 and metabolic profiles appeared unaffected by DT compared with warming alone. Our results suggest that DT places an additional energetic burden on the oyster, lowering the critical temperature. Nevertheless, tolerance patterns indicate resilience to DT, which may require a rebalancing of passive tolerance mechanisms, especially metabolic depression.

For nearly a century, scientists have tried to resolve the sensory physiology of chemical communication caused by predation stress. Only recently have we evidenced that abiotic stressors from a changing world, such as heat and ocean acidification, also trigger chemical communication between aquatic organisms - which we dubbed abiotic stress communication. Generally, the behavioural and physiological response to stress-induced cues are well understood, whereas the molecular mechanisms - cue identities, pathways of release, and perception - of this stress communication remain unresolved. Here, we propose a framework to organize the existing evidence for candidate mechanisms involved in abiotic stress-induced chemical communication, focusing on heat and acidification as two major abiotic stressors with environmental relevance. Drawing on transcriptomic, metabolomic and behavioural evidence, we propose that stressor-specific communication likely involves multiple cues and parallel routes rather than a single mechanism, such as membrane-related processes. We call for integrative work that links -omics with chemical profiling and ecological function assays to uncover the mechanisms of abiotic stress communication.

To understand how fish use vision to navigate, we must first understand what they see. This Review explores how visually guided navigation in teleost fishes is shaped by the structure of their visual systems, the cognitive processes that interpret sensory input and the dynamic environments they inhabit. With broad variation in habitat, ecology and visual capabilities, fish provide a powerful system for examining how sensory conditions influence navigation. We focus on short-range navigation and review core strategies - beaconing, pilotage, path integration and spatial mapping - alongside the visual and cognitive demands each entails. To assess which strategies are available to different species, we examine the visual processing pathway, from eye and retinal anatomy to behavioural evidence from cognition studies. These reveal that fish process visual information in a variety of ways to perform a diverse range of visual functions, including motion perception, object recognition and generalisation across viewpoint or lighting changes. We consider how sensory limitations and visual noise may constrain navigational accuracy, and how context or visual ability might shape which strategies are used. Environmental changes, such as turbidity, light pollution, or habitat degradation or shifts, can further degrade cue availability and reliability, affecting navigational performance. Understanding how visual information is received, processed and applied is therefore essential not only for interpreting observed behaviours, but also for predicting how fish may respond to changing environments. By linking sensory input with spatial behaviour, we propose a framework that integrates perception, cognition and movement, offering new insight into how diverse visual systems shape navigation across species.

Thermoregulation is an essential fitness-relevant process for nearly all ectothermic animals. Preferred or optimal body temperatures can be achieved through both behavioural and physiological mechanisms and the ecological importance and evolutionary context of these mechanisms have been well studied. Less understood, however, are the mechanisms driving variation in thermoregulatory decisions. With this Commentary, we emphasize the importance of understanding the sensory pathways and processes by which organisms translate information from their environment to thermoregulatory decisions and highlight the lack of essential empirical data in this field. Leveraging the rich literature of thermoregulation in lizards, we first synthesize established mechanisms of both behavioural and physiological thermoregulation. We then describe what is known about the sensory pathways and integration centres of the nervous system that transduce environmental information into thermoregulatory actions, via somatic and autonomic pathways. We provide guidance on how a better integration of sensory biology, endocrinology, animal behaviour and thermal biology will improve our understanding of key aspects of thermoregulation in ectotherms. Finally, we offer future directions to obtain a more cohesive understanding of thermoregulation, especially as cues and information in the environment continue to shift with climate change.

Many different types of insects make seasonal migrations over vast distances, typically from one broad geographical region to another, most often involving a latitudinal change in one direction in spring with a reversal of this direction in autumn. However, a small handful of these species instead migrate from an enormous geographical area to a highly specific destination they have never previously visited, a journey they make only once. Of these, only two - the diurnal monarch butterfly and the nocturnal bogong moth - are well studied. Even though these lepidopterans have sophisticated multisensory compass mechanisms to guide their long journeys, some studies question whether they are capable of navigating to their goal, or whether they just end up there more or less by chance, pushed by the prevailing winds (a 'stochastic wind-borne' transport mechanism). At the other extreme is the possibility that monarch butterflies and bogong moths are 'true navigators', with the ability to directly travel to their distant goal by using a 'compass' to guide them in their inherited migratory direction and a 'map' that continuously updates their current position. In this Review, we will argue that the evidence for stochastic wind-borne transport and true navigation is weak, and that the current weight of evidence supports 'vector navigation'. We present a hypothesis that individual Lepidoptera use vector navigation to migrate to a distant goal by employing favourable winds and global compass mechanisms to choose their desired flight directions during consecutive journey segments (or vectors), each of different length and direction, and with each vector transition being initiated by innate recognition of local sensory cues. We further hypothesise that this recognition is passed on to coming generations via epigenetic memory.