Visual uncertainty and task demands shape active sensing strategies in mice.

While prey capture has been extensively studied in pitcher plants, prey digestion, particularly the role of pitcher inhabitants in prey decomposition, has received little attention. We tested and compared prey decomposition among four Nepenthes species, which vary in pitcher traits and associated inquiline guilds. In a field experiment, 15 prey items were introduced into the digestive fluid of 120 newly opened pitcher tanks of four Nepenthes species and 30 water-filled artificial tanks. Half of the tanks of each type were bagged with insect-screening net and after 1 month prey count and degradation were compared between treatments. Whereas prey was recovered from all bagged tanks, a significant part was missing from the unbagged lidless artificial and N. ampullaria tanks. The probability of prey recovery also increased with tank height but did not decrease with the abundance of any inquiline guild, suggesting that missing prey was removed by external visitors. Prey degradation was greater in unbagged tanks, varied across species and increased significantly with the abundance of saprophages and plant detritus. These results highlight the involvement of inquilines and falling debris in prey breakdown in these carnivorous plants, with species-specific relative contributions, and they suggest a role of pitcher shape in protecting against kleptoparasitism. This article is part of the theme issue 'Life in natural microcosms'.

Barn owl color morphs hunt differently in moonlight.

Fatal attraction: flowers lure pollinators as prey in the carnivorous Drosera hookeri (Droseraceae).

Binocular integration is a well-established feature of neuronal processing in the primary visual cortex, where such integration is thought to first emerge. However, accumulating evidence demonstrates that subcortical retinorecipient nuclei possess sophisticated binocular processing capabilities, with important implications for cortical function, visual behavior, and non-imaging-forming physiology. This review synthesizes our current understanding of the circuit origins and functional relevance of binocular integration and modulation in the dorsal lateral geniculate nucleus, superior colliculus, and other subcortical targets. We describe how the definition of binocularity has evolved beyond simple ocular dominance to encompass diverse modes of neuronal modulation, including facilitation, summation, suppression, and emergent responses. We highlight the prevalence of multiple wiring motifs subserving binocular convergence, including direct retinal inputs, lateral circuits via local interneurons, feedback from cortical or subcortical sources, and indirect relays through intra- or interhemispheric connections. Recent anatomical and functional studies reveal substantial binocular integration despite apparent eye-specific input segregation, with region- and species-specific differences reflecting distinct ethological demands. Finally, elucidation of a critical role for subcortical binocular processing in prey capture and threat responses is expanding our cortex-centric view and revealing new complexity in the regional distribution of visual computations essential for survival behaviors.

Snake envenomation activates the immune system through permeability-increasing factors that generate an acute vascular inflammatory response by opening large inflammation-activated pores (IAPs) in the microvasculature. These events facilitate the exudation of plasma from blood into body tissues. However we show that IAPs also allow macromolecules, including venom toxins, to flood directly into the bloodstream, even against an outflow of plasma solutes. Such inflammation-facilitated macromolecular absorption (IFMA) acts together with lymphatic absorption and has a physiological role in removing interstitial molecules, as evidenced by our dextran studies. IFMA will function in vascular absorption of interstitial molecules, potentially up to the radius of IAPs, which we determined to be 21 nm (95% confidence interval (CI) 18-24 nm). This absorption depends on factors, including the interstitial-vascular concentration gradient, the reflection coefficient of each molecule and microvascular pressure. Molecules absorbed will include snake venom toxins and various cellular breakdown products that arise during processes such as the inflammatory phase of wound healing. Most, if not all, venom toxins will be absorbed, as these typically have a hydrodynamic radius (r0) of 1-6 nm, which is well below that of IAPs. Notably once in the circulation venoms cause distributed inflammation, enhancing venom toxin movement from the bloodstream into the tissues. These mechanisms markedly increase the absorption of often lethal snake toxins and ensure their dissemination throughout body tissues, facilitating prey capture and adding to make snakebite extremely dangerous to humans. These findings provide mechanistic insight into current empirical snakebite first aid and present directions that may improve these procedures. KEY POINTS: Snake venoms induce acute vascular inflammation, manifested by the opening of large pores termed inflammation-activated pores (IAPs), which we experimentally measure to have a radius of 21 nm. These pores mediate well-known exudation of plasma proteins but simultaneously provide a pathway for absorption of macromolecules, including venoms, a process that operates in parallel with the lymphatic system in clearing interstitial macromolecules. Although utilized in snakebite envenomation, such inflammation-facilitated macromolecular absorption (IFMA) is likely to have important physiological or pathophysiological roles, candidates including clearance of cellular breakdown products during the inflammatory phase of wound healing. Once in the vasculature venoms induce distributed inflammation of the IAPs, facilitating the exudation of venom toxins into tissues. The findings together with a model based on our experimental data provide new directions for improving snakebite first aid and present experimental evidence for a mechanism that operates to clear interstitial macromolecules.

Physiological responses of Mediterranean octocorals to prolonged exposure to ecologically relevant microplastic concentrations.

Serine proteases and serine protease inhibitors identified from the venom gland transcriptome of Rhitymna verruca.

While ecotoxicology has traditionally focused on impacts to reproduction and mortality, sublethal effects on behavior can also have important consequences that affect toxicity risk. Mercury is a potent neurotoxicant with well-documented effects on vertebrate behavior, although behavioral toxicity to invertebrates is understudied. Over a series of experiments, we assessed how a gradient of dietary methylmercury exposure influenced behavioral and physiological endpoints in dragonfly larvae, a widely used mercury biosentinel. Mercury exposure induced suboptimal behaviors in an artificially ideal trophic environment, suggesting potentially important impairments to prey detection and predator avoidance in larval dragonflies. For each doubling of dragonfly total mercury concentration, we estimated that dragonflies took 32 to 508 s longer to initiate foraging behavior and were 3% to 18% more active when exposed to a predation cue (95% confidence intervals). Other behavioral endpoints were unaffected by mercury exposure, including prey capture rates, foraging efficiency, and refuge use under predatory threat. Physiological endpoints, including growth, body condition, molting, wingpad symmetry, and immune response, were similarly insensitive to mercury toxicity. These results help support the utility of dragonfly larvae to monitor mercury in freshwater food webs and confirm that quantifying behavioral toxicity is important to fully characterize and mitigate exposure risk.

Comparative proteomic characterization of web silk toxins between two species of orb-weaving spiders Trichonephila clavipes and Nephilingis cruentata.

Efficient information acquisition is essential for survival, and the adaptive adjustment of self-generated signals in active sensing species offers profound insights into how animals solve sensory challenges. Horseshoe bats lower the frequency of their echolocation calls during flight so that echoes remain stable at a reference frequency (fref) despite Doppler shifts. Here we reveal a previously unrecognized function: it not only aligns echoes with the most sensitive frequency range but also suppresses background clutter noise to enhance prey detection. Using phantom echo playbacks and on-board recordings, we show that bats compensate for the highest-frequency echoes rather than the strongest ones. This shifts clutter echoes below fref, leaving a “silent spectral window” above it. Furthermore, recordings during prey capture and noise playback experiments show that spectral glints from fluttering moth wings appear in this window and are exploited for prey detection, illustrating how sensory systems are shaped for reliable information extraction in cluttered environments.

Charles Darwin was profoundly fascinated by Drosera (sundew plants), which have evolved as flesh-eaters with modified leaves, called traps, to catch small animals yet do not respond to transient mechanical stimuli. Despite Darwin's early insights, and recent advances in characterizing these mechanisms, our knowledge of the signaling molecules underlying prey capture responses remains limited. Here, we identify glutathione (GSH) as an important mediator within the signaling cascade of sundew carnivory, implicated in trap closure in a calcium-dependent manner. We show that prey capture promotes GSH accumulation in sundew leaves, while GSH depletion inhibits the movement. Furthermore, application of GSH is sufficient to induce trap closure across the Droseraceae family, including both the snap traps of Venus flytrap and the adhesive traps of sundew species. These findings advance our understanding of the enigmatic mechanisms of plant carnivory, a phenomenon that has intrigued scientists since Darwin's era.

Climate change is increasingly disrupting freshwater ecosystems in sub-Saharan Africa, posing severe threats to the reproductive success and population viability of key fish species. This study investigated the mechanistic effects of elevated temperature across a gradient and the combined impact of elevated temperature, acidification and hypoxia under a simulated future climate scenario (IPCC SSP5-8.5) on the reproductive physiology and early life stages of Clarias gariepinus in the Cross River Estuary. Single-stressor trials examined the effect of temperature (28-38°C) on oestrogen synthesis, cortisol levels and gonadosomatic index (GSI). A combined-stressor scenario (35°C, pH 6.2, dissolved oxygen 2 mg/L) was used to simulate predicted climate conditions. Each treatment was replicated across triplicate tanks, with 10 broodstock per tank, over an 8-week period. Environmental parameters were tightly controlled using aquarium heaters, aerators and pH regulators. Combined stressors markedly disrupted reproductive function. Oestrogen synthesis ceased at 34°C, coinciding with a sharp decline in GSI (r2 = 0.81, p < 0.001). Cortisol concentrations increased fourfold under concurrent heat and hypoxia. Cortisol concentrations increased fourfold under heat and hypoxia co-stress. Larval performance also declined sharply, with prey capture efficiency reduced by 33% at pH 6.0 and cumulative mortality reaching 82% by day 5 under combined-stressor conditions. Habitat suitability models projected a 71% reduction in spawning habitat availability in the estuary by 2070 under the SSP5-8.5 scenario. Genetic screening revealed a significant correlation (r2 = 0.63, p = 0.004) between heat shock protein 70 (HSP70) allele frequency and larval survival, indicating potential for adaptive resilience. These findings suggest a compounded vulnerability of C. gariepinus to climate-related stressors and highlight the potential need for targeted conservation efforts. Recommended interventions include habitat restoration, enhancement of dissolved oxygen regimes and selective breeding programmes to support thermal and hypoxic tolerance in vulnerable populations.

Giant suspension feeders have evolved repeatedly across vertebrates, but the relative roles of deterministic factors and phylogenetic contingency remain unclear. To test this, we integrate new selachian data with published pachycormiform and cetacean datasets to reconstruct phylomorphospaces from standardized cranial, dental, and jaw metrics (gape, orbit size, mechanical advantage, mandibular aspect ratio), evaluate convergence using quantitative metrics, and fit alternative multivariate evolutionary models. Independent lineages evolve from distinct macrophagous ancestors but follow roughly parallel trajectories into a shared morphospace region linked to efficient capture of small planktonic prey. Overlap is limited: pachycormiforms and filter-feeding selachians occupy adjoining areas, while mysticetes extend to a distinct endpoint along the same functional continuum. Convergence is strongest across clades, particularly between pachycormiforms and selachians, and comparatively weak within clades. Evolutionary modeling favors multiregime Ornstein-Uhlenbeck processes over Brownian or single-regime alternatives, identifying either three clade-specific optima or a shared optimum for pachycormiforms and selachians distinct from cetaceans. These results reveal repeated convergence on analogous functional designs stabilized around lineage-specific adaptive peaks. Giant filter-feeders thus illustrate how selective pressures can guide evolutionary direction, while historical constraints shape trajectories-showing determinism and contingency as complementary forces.

In adult spiders, leg lengths vary within and between species and is associated with functions in web construction, sensory activities, and prey capture. However, little is known about how leg proportions change during ontogeny. Here we investigate whether leg length relative to body size is maintained throughout development in three cobweb spiders (Latrodectus geometricus, L. mactans, and Steatoda grossa). Because spiderlings of these species build webs and capture prey from the first instar, we predicted proportional growth across instars. We also evaluate which model (linear, quadratic, or Gompertz) best describes femur and tibia growth, and estimated growth rates (first derivative) and accelerations (second derivative) for each sex and species. Legs were proportionally shorter in early than in later instars in L. geometricus and S. grossa, whereas proportions remained similar across development in L. mactans. Femur and tibia growth was best described by a quadratic model in both sexes of L. geometricus and L. mactans, and in males of S. grossa. In contrast, females of S. grossa followed a Gompertz trajectory; with high early growth rates that declined toward maturity. Despite these differences in trajectories, leg segments showed similar magnitudes of acceleration within species. Across the three theridiid species, females showed two distinct ontogenetic patterns-steady increases in growth rate (quadratic) or rapid early growth followed by deceleration (Gompertz)-whereas males consistently followed quadratic trajectories. Conserved acceleration among leg segments may reflect developmental canalization that preserves functional proportionality during growth.

Echolocating bats operate within a closed sensorimotor loop in which call emission, echo reception, sensory processing, and motor response are linked by finite propagation delays and bounded response times. Although synchrony between wingbeats and call timing is frequently observed, it remains unclear when such coordination is temporally feasible and when it must necessarily break down. Here, I develop a constraint-based framework formalising how temporal feasibility limits shape wingbeat-call coordination during active echolocation. Building on the responsivity framework, the analysis derives explicit conditions under which call emission remains phase-locked to a cyclic motor rhythm, and identifies regimes in which phase locking becomes progressively infeasible as acoustic delay shrinks and call rate rises during prey approach. Simulations across three motor-control configurations-fixed wingbeat frequency and excursion, dynamically adjusted frequency, and dynamically adjusted frequency and excursion-show that transitions from synchrony to asynchrony arise as necessary consequences of delayed feedback and bounded motor dynamics, rather than discrete changes in behavioural strategy. Increasing motor flexibility extends the synchrony-permissive range of call rates but does not eliminate the feasibility boundary. Simulation ensembles spanning biologically plausible parameter combinations confirm that regime transitions are robust and that asynchronous call phases exhibit structured clustering near the feasibility boundary. Empirical observations of transient decoupling during prey pursuit and the terminal buzz are consistent with these predicted transitions. The results identify temporal feasibility as a governing constraint on echolocation behaviour, clarify how apparent closed-loop coordination can arise without tight motor coupling, and generate testable predictions for when and why wingbeat-call synchrony must fail during prey capture.

Aerial-hawking bats adjust their biosonar in the search, approach and capture phases of echolocation to guide aerial prey interception. Some bat species have secondarily evolved a gleaning strategy that relies on passive acoustic cues to detect and capture prey on vegetation. Here, we tested the hypothesis that such a gleaning specialist, the fringe-lipped bat, Trachops cirrhosus, must use stereotyped aerial-hunting echolocation phases, including a buzz when opportunistically capturing aerial prey. Using data from sound-recording tags on 8 individuals, we reject this hypothesis by showing that fringe-lipped bats can detect and intercept aerial prey by echolocation but do so with modest biosonar adjustments and without producing a high-resolution buzz. These findings challenge the notion that the stereotyped echolocation phases of hawking bats are required for aerial prey capture and show that echolocation is an extremely versatile sensory system that can be employed across otherwise specialized foraging niches.

The Dasyurid species Sarcophilus harrisii, Dasyurus maculatus, and Dasyurus viverrinus, occupying diverse ecological niches and forming a guild structure in Tasmania, provide a basis for examining the roles of various forelimb muscle groups in prey capture and locomotion. Muscle fiber architecture is a key contributor to muscle force and can indicate specialized, repeated forelimb engagement. We performed wet dissections and virtual dissections via computed tomography to provide the first modern descriptions for the three species. We also quantified intrinsic forelimb muscles and compared normalized physiological cross-sectional area (PCSA) across species for individual and grouped muscles. The topology and muscle PCSAs are similar across species with select functional groups showing slight deviations. Overall proportions and ratios between antagonistic muscle groups reveal that D. viverrinus shows an overall reduction in muscle PCSA, whereas S. harrisii and D. maculatus appear to show an emphasis on muscle groups engaging in specialized behaviors for prey processing and arboreal locomotion, respectively. The results support the known trend of conserved forelimb musculature in marsupials. Nevertheless, muscle PCSA remains an important biomechanical indicator for specialized forelimb use in dasyurids.

Cnidocytes (stinging cells), unique to cnidarians (corals, anemones, jellyfish), have diversified into distinct types with variable forms and functions. Nematocytes, cnidocytes found in all cnidarians, are used for prey capture and defense. When triggered, a pressurized capsule inside the nematocyte releases a harpoon-like structure attached to a hollow tubule that pierces prey and delivers venom. Ptychocytes, a cnidocyte unique to tube anemones (sister to corals and sea anemones) discharge a long spineless tubule used exclusively to build the tube in which the animal lives. Given that nematocytes and ptychocytes are specialized for different functions, we hypothesized that they might respond to firing cues in different ways. To test this, we examined the morphology, function, and distribution of nematocytes and ptychocytes in the North American Tube Anemone, Ceriantheopsis americana. We determined that ptychocytes have apical sensory structures like the cones previously described on nematocytes. Surprisingly, the body wall has a dense population of multiciliated cells that appear to function in tube formation. To determine how divergent selection pressures may have affected firing dynamics, we compared the discharge kinematics of cnidocytes from C. americana and the model sea anemone, Nematostella vectensis. Both nematocytes and ptychocytes from C. americana fired slower than nematocytes from N. vectensis, suggesting the rapid discharge speed of sea anemone nematocytes resulted from modification to these cells after sea anemones and tube anemones diverged from their common ancestor. By comparing the morphology and function of different cnidocytes, we can reconstruct the steps that gave rise to cnidocyte diversity.

The insecticidal molecules of spiders persistently evolve to ensure rapid paralysis of their prey, and the best molecules are transmitted to their progeny. Here, we cloned two insecticidal peptides, Bs2 and Bs3, from the venom glands of the theraphosid Brachypelma smithi. Bs2 and Bs3 are 90.2% identical, but they exhibit interesting structural differences at their C-termini, including a connecting disulfide bond (residues Cys15-Cys36 for Bs2 and Cys15-Cys30 for Bs3). The genomic origin of Bs2 and Bs3 may be a cause for gene duplication events. Moreover, Bs2 differs in two residues from Tal1 (95.1% identical), an insecticidal peptide, from the tarantula Tliltocatl albopilosus. Likewise, Bs3 is similar to Asp3a from Aphonopelma sp., a peptide that targets mammalian Cav (voltage-dependent Ca2 + channel), but it has not been tested in insects. Bs2 and Bs3 were cloned and recombinantly expressed in bacterial cells, and their paralytic effects were tested on three species of insects. The insecticidal peptide rBs2 with the connecting loop Cys15-Cys36 was significantly more insecticidal than that of rBs3 when affecting Galleria mellonella larvae (Lepidoptera). Yet, the insecticidal peptide rBs3 with the connecting loop Cys15-Cys30 was significantly more insecticidal than that of rBs2 when affecting Acheta domesticus nymph crickets (Orthoptera), and Gromphadorhina portentosa cockroaches (Blattodea). rBs2 and rBs3 structural models show a low-structured C-terminal in rBs3, which correlates with a more flexible amino acid sequence of such C-terminal from residues Tyr30 to Leu42. Since insecticidal spider peptides are constantly evolving for prey capture, they are valuable ion channel antagonists for understanding insect cell receptors, and they are also promising leads for insect control.