Journal of Experimental Biology最新文献

Species recognition and courtship behaviors are powerful drivers of speciation. Here, we investigate the neural and behavioral signatures of species recognition in Upland chorus frogs (Pseudacris feriarum). Populations of this species that are sympatric with congener/s (e.g., P. nigrita) have evolved divergent male mating calls and enhanced acoustic discrimination by females due to costly interspecific hybridization. Herein, we examined evoked neural activity and behaviors in male P. feriarum in response to sympatric, allopatric, heterospecific calls, or silence via phospho-S6 immunofluorescence. The sympatric call evoked activity in several brain regions that regulate spatial navigation and social decision making, indicating that this call type may be an important trigger for navigating to and within a complex chorus environment. Moreover, each stimulus resulted in a unique pattern of coactivation among brain regions. Despite these neural changes, there were no differences in behavioral response to each stimulus. Our results suggest that signal input and behavioral output are coded independently in the brains of male chorus frogs. Together, these findings represent a first step towards understanding the neural basis of conspecific recognition in a system where this trait contributes to ongoing diversification.

A predator's survival is highly dependent on correctly deciding whether to attack potential prey. Pursuit predators, for example, can estimate the size of a moving target from the ratio between its angular speed and size. Such heuristic rules are not available, however, when ambushing stationary prey. Here, we investigated how pixie robber flies (Psilonyx annulatus) and damselflies (Ischnura posita) hunt stationary prey using different sensory strategies, relating to their marked differences in eye morphology. We show that pixie robber flies assess prey using whole-body translational movements. During this assessment, the prey is outside the pixie robber fly's stereopsis range, yet attacks are launched from a distance dictated by absolute, not angular, prey size. These findings suggest that pixie robber flies use motion parallax to infer three-dimensional cues, such as prey distance and/or size, before attacking. Motion parallax may be particularly suitable for pixie robber flies as they hunt in cluttered, low-lighting conditions and have a small size, making it difficult for potential prey to detect their movement, even in close proximity. Damselflies probably rely on alternative processes to assess prey, as translational movements are absent in the assessment phase.

Parasites with complex life cycles produce large numbers of free-living infectious stages to overcome the low odds of successful transmission between hosts. These stages often infect non-competent or 'dead-end' hosts, which cannot support parasite development or transmission. While typically viewed as ecological cul-de-sacs, dead-end hosts may still experience meaningful effects from parasite exposure. Here, we examined how exposure to Paragordius varius hairworm larvae influences behaviour and development of Physella acuta, an invasive freshwater snail likely functioning as a dead-end host in this system. Using a dose-response design under controlled conditions, we exposed juvenile snails to increasing larval concentrations and tracked activity over 24 h in relation to water, total home range and core activity areas. Snails were then reared to assess impacts on shell development. Infection intensity scaled with larval dose. At the highest exposure, snails showed an almost one-third reduction in home range, spent substantially more time submerged and entered water less frequently but for longer durations. These shifts indicate reduced exploratory behaviour and altered water use, potentially limiting ecological flexibility. Although shell size and shape were unaffected, shell crush resistance increased markedly with dose, suggesting altered properties tied to behavioural or physiological responses. Our results show that parasites can impose sublethal yet ecologically significant costs on dead-end hosts. This challenges traditional views of dead-end hosts as passive endpoints and highlights their potential role in shaping host-parasite dynamics. For invasive species such as P. acuta, even non-transmissive infections may carry fitness and ecological consequences.

The evolutionary arms race between insectivorous bats and moths has driven the development of elaborate anti-predator strategies, with ultrasound hearing considered a key adaptation in tympanate moths. However, whether this sensory capability translates into more effective evasive flight compared with earless moths, and whether last-ditch maneuvers are effective against high-duty-cycle (HDC) bats remains unresolved. We integrated controlled laboratory predation experiments involving three horseshoe bat species (Rhinolophus episcopus, Rhinolophus osgoodi, Rhinolophus sinicus) with field dietary analysis to address these questions. We found that while eared and earless moths shared a similar repertoire of flight maneuvers, eared moths more frequently employed the most effective tactics (e.g. flight cessation and erratic flight) and initiated behavioral transitions significantly faster upon bat attack. Flight behavior was the primary determinant of predation outcome, with flight cessation being the most effective strategy (12% predation), contrasting sharply with the high vulnerability of stationary wing fluttering (76% predation). In laboratory trials, eared moths experienced 14% lower overall predation probability than earless moths. This advantage was strongly corroborated by field data, which showed eared moths were disproportionately underrepresented in bat diets compared with their own abundance in the habitat. Our results demonstrate that moth last-ditch flight maneuvers are effective against HDC bats and that ultrasound hearing confers a significant survival benefit by enabling earlier and more strategic deployment of evasive flight. This supports a hierarchical model of anti-predator defense, where advanced sensory systems refine the performance of ancestral escape behaviors, shaping the dynamic bat-moth arms race.

Water supply is essential for most physiological processes, making its efficient use vital for the organism, especially in hot and dry periods. The tegu lizard Salvator merianae, which is abundant in regions characterized by cool and dry winters, exhibits temperature-independent dormancy. Dehydration is known to affect physiological-behavioural performance, but the role of water availability in dormancy in tegus remains uncertain. This is particularly important in the current context of climate change, marked by more frequent heat waves and longer dry seasons. Thus, we investigated whether hydration state influences winter metabolic and behavioural reductions in male and female tegus. From April to September, we measured plasma osmolality, haematocrit, plasma ammonia concentration, body temperature (Tb), activity rate (overall dynamic body acceleration via triaxial accelerometry), specific behaviours (exploration, sheltering and resting), body mass and body condition factor in control and dehydrated individuals during pre-dormancy (April-May), dormancy (June-July) and post-dormancy (August-September) phases. Dehydrated tegus exhibited higher plasma osmolality and Tb compared with controls, whereas haematocrit, plasma ammonia concentration, body mass, body condition factor, activity rate and specific behaviours were similar between groups throughout the experimental months. Both control and dehydrated animals showed coordinated reductions in activity rate and behavioural expression during the pre-dormancy and dormancy phases, followed by increases during the post-dormancy phase. These results indicate that hydration state does not play a role as a driver of dormancy in tegus during moderately cold and dry winters; however, dehydration may be a risk factor for superheating during prolonged dry seasons and frequent heat waves.

Ectotherms are thought to be particularly vulnerable to climate change as they rely directly on environmental temperatures to regulate their physiology. One of the pathways by which ectotherms can alter their physiology in a warming environment is through phenotypic plasticity, which is usually treated as resulting from interactions between the organism's genetics and the environment. However, ectotherms also host communities of microbes which can change quickly within the host and affect host physiology. To date, little is known about the extent to which gut microbes affect thermal plasticity in the non-model host organisms that will be the most affected by climate change. We investigated relationships between gut microbiome composition and host heat tolerance plasticity in three species of Anolis lizards: Anolis cristatellus, Anolis sagrei and Anolis carolinensis. We brought wild-caught lizards into the lab and tested for (1) effects of experimental warming on the gut microbiomes and (2) associations between microbiome composition and compositional dynamics with heat tolerance and its plasticity across host individuals and species. We found that each anole species hosted a distinct gut microbial community, but that all host species had microbiomes that were largely resilient to temperature increases. However, several key aspects of microbiome composition were correlated with baseline host heat tolerance. Finally, microbiome composition and its stability were associated with the magnitude of plasticity in host heat tolerance. Our results indicate that gut microbes may play a role in the ability of ectotherms to mount plastic responses to rapidly changing thermal environments.

Object motion is a fundamental visual cue for many animals, yet its role in modulating visual perception is not fully understood. The majority of previous studies have used stationary stimuli to investigate the visual acuity of insects like honeybees. Here we use a behavioural assay to investigate whether object motion influences the known bounds of bees' visual acuity. Using a Y-maze, we conducted binary choice experiments where honeybees (Apis mellifera) were trained to a stimulus and then tested with pairs of stimuli varying in shape (disc vs. diamond), size, and motion (stationary vs. moving). When stimuli were stationary, bees perceived the change in shape only for targets that subtended visual angles >1.9°. However, when presented with a stationary and a moving stimulus, they consistently preferred the moving stimulus, even when both stimuli subtended angles as small as 0.44°. Furthermore, motion cues were found to override a learned preference for a familiar stationary shape. Most notably, bees successfully discriminated shapes at the smallest tested size of 0.44° when both targets were in motion, but not when they were stationary. These findings provide behavioural evidence that object motion can be a salient cue that not only drives choice but also enhances visual acuity in honeybees beyond previously established limits. This suggests that motion may facilitate the perception of fine spatial details and underscores the importance of incorporating dynamic cues when studying the sensory limits of animal vision.

The ability to prioritize relevant stimuli over distracting ones is essential for adaptive behavior, particularly in species with limited sensory systems. In the mudflat crab Neohelice granulata, a moving object on the ground (dummy) can elicit either avoidance or pursuit, indicating that the same stimulus may be interpreted as predator or prey. Previous studies have shown that the probability of these opposite responses depends on both stimulus features (e.g., size, speed) and intrinsic animal attributes (e.g., sex, hunger level). Here, we investigated how social context-a factor independent of both stimulus properties and individual traits-affects responses to the dummy. Using a controlled experimental design, we tested whether the presence, proximity, and behavior of a conspecific of the same or opposite sex modulate individual responses. We found that, irrespective of sex, crabs tested in pairs showed significantly reduced exploratory activity and a lower probability of responding to the dummy compared to solitary crabs. Notably, this reduction occurred only when individuals were within 15 cm of each other. Furthermore, in the presence of a conspecific, crabs-initiated avoidance or predatory responses at shorter distances to the dummy, suggesting delayed decision-making due to divided attention. In contrast, freezing distance remained unchanged across social conditions, indicating that active responses such as escape or predation are selectively modulated by social proximity. Overall, our results reveal a complex interplay between social context, attention, and decision-making. Crabs adjust their perceptual and behavioral strategies according to social cues, highlighting the influence of social factors on survival in fluctuating environments.

Division of labour in honey bees is based on a process of behavioural development where the worker bee successively performs different tasks at different ages. Workers start with tasks within the nest and move on to become foragers. In Apis mellifera, juvenile hormone and vitellogenin are major drivers of this behavioural maturation, which is accompanied by changes in brain physiology including changes in neuronal gene expression and synaptic connections. Based on this detailed knowledge we asked whether and how major characteristics of the behavioural maturation process vary among two tropical Asian honey bee species, the phylogenetically ancestral open-nesting A. florea and the cavity-nesting A. cerana, a sister species to A. mellifera. Our behavioural studies show that workers of A. florea exhibit a slower pace of behavioural maturation compared to A. cerana, with greater individual variation in the age at onset of foraging. In both species the expression pattern of JH and foraging associated transcription factors broadly mirrored those reported for A. mellifera. In contrast, expression dynamics of vitellogenin and nurse-associated transcription factors in both species did not show the clear age- or task-related pattern as reported for A. mellifera. Notably, workers of A. florea consistently exhibited substantially higher vitellogenin expression levels than A. cerana workers. Based on our findings, we propose that evolution of accelerated behavioural maturation in cavity-nesting species is primarily attributed to changes in the temporal dynamics of juvenile hormone signalling, whereas vitellogenin levels might vary according to different social functions.

The black soldier fly Hermetia illucens (BSF) is increasingly studied for its ability to convert organic waste into protein, offering solutions for waste valorisation and livestock feeding. Adult performance is critical for egg production, yet the behavioural and molecular bases of sugar feeding in adult BSF remain poorly understood. To fill this gap, we combined behavioural assays, morphological analyses, electrophysiological recordings, and gustatory receptor (GR) repertoires and expression. All the experimental tests conducted in this study converge to show that the adults can detect and consume sucrose, with females responding more strongly than males. Genome analysis identified 28 GRs, a surprisingly small number for a generalist fly, including only three putative sugar-specific GRs homologous to those of the eight known sugar GRs in Drosophila. Moreover, one of these GRs show a general high level of expression including in the head and in the antennae whereas the two others display tissue-specific patterns of expression. We also identify a high number of GR pseudogenes, including four putative sugar receptor pseudogenes, indicating multiple gene loss events of GRs compared to other dipterans sharing a similar ecological niche. Despite this reduced GR repertoire, adult BSF retain strong behavioural and physiological sensitivity to sugars in their environment. The set of behavioural, morphological, and electrophysiological tools developed here provides a foundation for deeper investigations into feeding behaviour in this species of growing agroecological importance.