Journal of Comparative Physiology A

OverviewThis dataset originates from a preliminary respirometry study on carabid beetles from the Elbe Estuary (Northern Germany), encompassing species from freshwater and saltmarsh habitats along a salinity gradient. The study was designed to establish and validate a workflow for measuring oxygen consumption, including chamber setup, sensor recording, drift correction, and calculation of absolute and mass-specific metabolic rates. Oxygen consumption was measured for five species (Carabus auratus, Carabus granulatus, Limodromus assimilis, Poecilus versicolor and Pterostichus niger) using sealed glass vials connected to an optical oxygen system. The dataset provides individual-level measurements and serves primarily as a methodological reference for future respirometry studies on ground-dwelling arthropods. The O2 consumption rates of carabid beetles showed interspecific differences and followed metabolic scaling theory, revealing an inverse relationship between body mass and mass-specific metabolic rates across species (Figure 3). O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=127 SRC="FIGDIR/small/720111v1_fig3.gif" ALT="Figure 3"> View larger version (17K): org.highwire.dtl.DTLVardef@f41f27org.highwire.dtl.DTLVardef@12939eeorg.highwire.dtl.DTLVardef@19a4630org.highwire.dtl.DTLVardef@17611ba_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 3:C_FLOATNO Oxygen consumption rates of Carabid species per (a) animal in [ml O2 h-1] and as (b) mass-specific consumption rate [ml O2 h-1 g-1]. Points represent mean oxygen consumption per individual (C. auratus: n = 2; L. assimilis: n = 6; P. versicolor: n = 7; P. niger: n = 6). C_FIG

Vestibular neurons are core elements of the pathways involved in vestibulo-motor functions, such as vestibulo-spinal and vestibulo-ocular reflexes. To meet behavioral needs, electrophysiological neuronal properties are adequately adapted to the sensory-motor computation sustaining these distinct vestibular reflexes. During frog metamorphosis, there is a complete reorganization of the posturo-locomotor system while the oculomotor system remains minimally changed, probably associated to so far unknown changes in vestibular neuronal properties. We used this unique model to investigate the central developmental mechanisms underlying such a reconfiguration of vestibular-associated behaviors. Central vestibular neurons exhibit two types of electrophysiological phenotypes: tonic neurons with a continuous discharge and phasic neurons with a transitory discharge mainly due to the activation of Kv1.1 channel. Electrophysiological recordings and Kv1.1 immunolabeling of vestibulospinal (VS) and vestibulo-ocular (VO) neurons at both larval and juvenile stages revealed that the majority of VS neurons exhibited a tonic discharge in larvae but a phasic discharge in juvenile, while VO neurons remained mainly tonic throughout development. Changes in phasic and tonic neurons proportions in VS population are partly explained by neurogenesis. But we provide evidences that an electrophysiological phenotype switch is a concomitant developmental mechanism participating in the maturation of these central vestibular neurons. All together our results showed that the maturation process in central vestibular neuronal groups is highly related to the metamorphosis-induced remodeling of vestibulo-motor functions they are involved in, with the ultimate purpose of ensuring an adequate adaptation of neuronal elements properties to the developmental changes of behavioral constrains.

The electrophysiological process of auditory transduction in insects remains largely conjecture due to the unknown role of ion channels localised to the cilia, but experimental evidence supports either NompC or Nan-Iav as the auditory mechanotransduction ion channel. Here, we knocked down two key genes that code for the two candidate sound-activated ion channels using dsRNA-mediated RNA interference. We measured sound-evoked activity of the auditory nerve and intracellular electrical currents from the ciliated ending of individual auditory receptors. We found that the sound-evoked nerve activity was reduced in nompC, nan and ift88 knockdown. Using whole-cell patch clamp recordings we found that nompC and nan knockdown resulted in reduced sound-evoked transduction current. Stochastic depolarisations hypothesised to be mediated from one of the candidate mechanotransduction ion channels, either NompC or Nan-Iav, where not affected by knockdown of either channel. The discrete depolarisations are therefore mediated through another unidentified ion channel. We test the hypothesis that discrete depolarisations are graded action potentials that travel toward the soma through noise analysis of the transduction current and analysis of discrete depolarisations to voltage-steps. As a positive control we also knocked down ift88, a protein essential for transporting proteins, including ion channels, along the cilium and found both the transduction current and the discrete depolarisations decreased. Key pointsO_LIInjection of dsRNA decreased RNA of nompC and nan C_LIO_LISound-evoked nerve activity is reduced for RNAi-mediated knockdown of nompC and nan C_LIO_LINompC and Nan both contribute to the transduction current C_LIO_LIThe stochastic discrete depolarisations are not due to NompC or Nan-Iav ion channel but to a third unidentified ion channel. C_LIO_LINoise analysis of the transduction current and the discrete depolarisations suggests they are graded action potentials that travel in the direction of the soma. C_LIO_LIKnockdown of ift88 reduced both the transduction current and discrete depolarisations. C_LI Significance StatementInsects are important to understand, economically, agriculturally and medically. However, we still do not understand fundamental aspects of how insects detect their own body movements, vibrations and sound. These senses are detected by insect chordotonal organs, specialised miniaturised mechanoreceptors that convert movements into electrical signals through specialised ion channels. Previous experimental work has advocated either NompC or Nan-Iav as the mechanosensitive ion channel. Here, for the first time, we reduced the expression of both nompC and nan and measured the sound-evoked transduction current directly from neurons in a specialised auditory chordotonal organ. In contradiction to previous studies, we show that both ion channels contribute to the transduction current and find that electrical signals termed "discrete depolarisations" travel toward the soma.

Animals rely on a wide range of environmental signals, including celestial and terrestrial cues for navigation. While celestial cues, such as the sun, play a major role in maintaining a constant heading during long-distance migration and dispersal, terrestrial cues provide an animal with a short-range navigation system, ideal to pinpoint highly specific locations. In Monarch butterflies, the simulation of a terrestrial landmark, i.e. a vertical stripe, induces an attraction behavior (all animals head toward the stimulus) while a small green light spot, simulating the sun, elicits menotactic orientation (animals adopt individual-specific headings relative to the stimulus). However, the mechanisms underlying how the animal distinguishes between a stimulus as a terrestrial landmark versus a celestial cue remains unclear. To explore this, we tested non-migratory Monarch butterflies (Danaus plexippus) in a flight simulator. The inner surface of simulator was equipped with an area of LEDs, allowing to present different visual stimuli to the butterflies during tethered flight. By systematically manipulating the stimulus width, height, brightness, and elevation we found that Monarch butterflies exhibited attraction behavior to high contrast areas, like stripe edges. Menotactic behavior was not achieved by solely decreasing the stimulus to a small light spot but also required for the stimulus to be presented at higher elevation to be interpreted as a sun stimulus. These findings suggest that multiple parameters, inherently set by the butterflys navigation system, are critical to interpret a visual stimulus as celestial cue or terrestrial landmark, producing dynamic switches between different orientation strategies during navigation.

The energetic demands of courtship are central to sexual selection, but their magnitude and temporal variation remain poorly quantified in many signalling systems. We used closed-chamber respirometry and low-light video analysis to estimate courtship-associated metabolic rates in males of the bioluminescent ostracod Photeros sp. EGD. Low-activity metabolic rate varied strongly across the diel cycle: in small vessels that constrained movement, individually measured males consumed significantly more oxygen at night than during the day. We then compared oxygen consumption across vessels that differed in opportunities for movement and courtship. Metabolic rates were highest in large vessels that permitted bioluminescent courtship displays, intermediate in medium vessels that allowed swimming but not full displays, and lowest in small vessels that constrained movement. Oxygen consumption in large vessels at night was approximately 500% of small-vessel daytime rates, 280% of small-vessel nighttime rates, and 160% of medium-vessel nighttime rates. Because measurements integrated oxygen use over multi-hour intervals, these values represent time-averaged metabolic demand rather than instantaneous costs of individual light pulses or display trains. Video analyses suggested a positive association between signalling rate and oxygen consumption, although this relationship was not statistically supported in our large-vessel dataset, which had low statistical power. Together, these results show that male Photeros undergo strong diel shifts in metabolic state and that the whole-animal performance required to construct bioluminescent courtship displays may often impose substantial energetic demands.

Skylight polarisation patterns provide a critical navigational cue for many insects. Bees perceive these patterns through specialised ommatidia in the dorsal rim area of their compound eyes, enabling them to estimate the suns direction and navigate between food sources and the hive. Although polarisation-based navigation has been extensively studied behaviourally, computational models that link DRA anatomy with navigational performance are lacking. Here, we simulate polarisation vision in honeybees (Apis mellifera) and bumblebees (Bombus terrestris) using real sky polarisation images to capture biologically relevant skylight properties. Our biologically grounded simulation incorporates species-specific DRA anatomy, including ommatidial optical axis directions, photoreceptor receptive fields, and microvillar orientations. We evaluate navigational accuracy and consistency across sun elevations under two distinct, potentially complementary navigational models: the matched filter, which requires scanning across body orientations to identify the solar axis, and the vector-sum model, which generates instantaneous sun azimuth estimates from a single body orientation, making it independent of active scanning. Matched filter errors in estimating solar axis are below 5{degrees} across most sun elevations and in both species. Absolute errors in the vector-sum model are lower for honeybees than bumblebees (median [~]10{degrees} and [~]30{degrees}, respectively), reflecting differences in DRA anatomy, particularly viewing direction and microvillar arrangement. Both models allow stable course control across most sun elevations in both species, yet the matched filter, being limited to solar axis alignment, only enables positive or negative phototaxis. Overall, this work provides a mechanistic and comparative framework based on realistic DRA anatomy to study polarisation-based navigation, generating testable predictions for insect navigation under natural sky conditions. Author SummaryMany insects, including bees, navigate with the help of skylight polarisation patterns which hold information about the suns position even when it is not visible. Bees detect these patterns through the dorsal rim area (DRA) of their complex eyes. How differences in DRA anatomy between bee species translate into differences in navigational ability has remained unclear. Here, we built a biologically realistic simulation of polarisation vision in honeybees and bumblebees. We used real sky images to examine what polarisation information is available to each species. We then tested two models of sun position estimation based on the polarisation pattern: one that requires the bee to actively scan the sky, and one that generates an instantaneous estimate from a single body orientation. In both species, both models show that accurate sun position estimation and stable navigation are possible using just polarisation information under a wide range of sun elevations. Differences in navigational performance between honeybees and bumblebees arise because the two DRAs look at different parts of the sky. Our results provide a robust framework for understanding how DRA anatomy shapes polarisation-based navigation in bees.

Superposition compound eyes improve sensitivity by pooling light from multiple facets and are widespread among nocturnal insects, including moths and beetles. Optical theory predicts that superposition eyes must be nearly spherical to form coherent images and therefore lack highly pronounced acute zones with high spatial resolution. To examine this, we imaged eyes of six hawkmoths (Sphingidae) spanning diurnal and nocturnal activity with high-resolution microcomputed tomography. Our automated pipeline created detailed eye maps quantifying morphological parameters. We measured local eye curvature (radial distance), interommatidial angle ({Delta}{varphi}), facet size and crystalline cone skewness (tilt of cone axes relative to the local surface normal). All species show more curvature in the dorso-ventral plane with flattening in the antero-posterior plane. However, their eyes still retain near-spherical curvature globally, with diurnal species showing greater distortion. For facet parameters, spatial acuity is generally highest (lowest {Delta}{varphi}) near the eye center and decreases gradually toward the periphery. However, overall variation in spatial acuity is low and these eyes lack distinct acute zones. Facet size gradually changes from center to periphery, increasing in some species and decreasing in the others. Cone skewness is present in all six species (0{degrees}-10{degrees}), but in two diurnal species of hummingbird hawkmoths it increases markedly in the posterior region (15{degrees}-30{degrees}) possibly compensating for regional eye flatness. This paper provides foundational data of ommatidial and eye shape measurements and advances our assumptions about how superposition eyes function.

Environmental warming is generally expected to increase metabolic demand in ectotherms. However, facultatively endothermic insects such as bumblebees regulate body temperature and may reduce thermogenic investment under warm conditions, potentially altering physiological performance and responses to climate change. We combined flow-through respirometry and infrared thermography to test how elevated ambient temperature (25 vs 35{degrees}C) affects feeding energetics and postprandial metabolism in the bumblebee Bombus terrestris. Bees maintained substantially lower thoracic temperature excess at 35{degrees}C than at 25{degrees}C, both before and during feeding. Feeding metabolic rate was also lower at 35{degrees}C and was strongly positively associated with thoracic temperature excess, indicating that feeding energetics were primarily explained by thermoregulatory state rather than ambient temperature alone. Elevated temperature reduced both the probability and energetic magnitude of specific dynamic action (SDA), including total SDA expenditure, early postprandial metabolism, and peak metabolic amplitude. In contrast, SDA duration and time to peak response showed little temperature dependence. Our results demonstrate that warming can suppress energetic expenditure in facultatively endothermic pollinators by limiting thermogenic investment and postprandial metabolic responses, potentially constraining the energetic flexibility underpinning foraging performance under climate warming.

The shift to terrestrial environments in ancestrally aquatic animals is often associated with key physiological and physical changes, including shifts in respiratory physiology and in some cases, even the evolution of completely novel respiratory structures. Examining how respiration operates across a gradient of submersion states in ancestrally aquatic terrestrial animals may shed light on how complex biological traits shift under different selective regimes. In this work, we begin exploring respiration in terrestrially-adapted land crabs that still use their gills to respire while underwater. We tested the relationship between aquatic respiratory rates, body size, and sex in red devil vampire crabs (Geosesarma hagen) at two ecologically-relevant temperatures. We found small females respire more than small males at 28{degrees}C, while large females respire more than large males at 21{degrees}C. Additionally, body size is a significant factor affecting respiratory rates of both sexes at 21{degrees}C and warmer temperatures significantly increase respiration in small crabs of both sexes. Interactions between these factors also led to emerging trends that can be explained by both physiological rules, such as reproductive investment and surface-to-volume ratios and heat transfer. We also report a temperature coefficient (Q10) of 1.52 for this species, showing an expected 52% change in respiratory and metabolic rate for every 10{degrees}C increase. This work also demonstrates the importance of understanding how and to what extent biological variables like sex and body size interact with abiotic environmental factors when measuring physiological traits in ectothermic invertebrate animals.

Hypoxia (low oxygen availability) is a common environmental stressor in estuarine ecosystems that negatively affects fish survival as well as physiological and behavioral responses. However, the effects of hypoxia on the brain remains poorly understood, particularly in non-model species. Here, we investigated how prolonged hypoxia influences neural, vascular, and molecular responses in the brain of the speckled sanddab (Citharichthys stigmaeus), an ecologically relevant estuarine flatfish. Fish were exposed to normoxic or hypoxic conditions for seven days, and responses were assessed using histological analyses of neural proliferation and vascular structure, alongside transcriptomic and proteomic profiling. Hypoxia increased neural cell proliferation and progenitor activation in the hypothalamic nucleus recessus lateralis (NRL) and optic tectum, while reducing survival of newly generated cells. At the tissue level, hypoxia induced region-specific vascular remodeling, characterized by increased vessel area and vessel number without evidence of widespread endothelial proliferation. At the molecular level, transcriptomic and proteomic analyses revealed consistent enrichment of biological processes related to stress responses, development, metabolism, and cellular homeostasis, despite limited overlap between individual genes and proteins. Gene- and protein-level analyses further indicated activation of hypoxia-responsive pathways, including HIF signaling and oxidative stress protection, alongside selective metabolic reprogramming. Together, these findings demonstrate that hypoxia induces multi-level changes in the brain, linking neural plasticity, vascular remodeling, and molecular responses. This integrated response likely supports brain function under reduced oxygen availability in dynamic estuarine environments and highlights the role of the brain in regulating responses to environmental stress.

Many insects enter diapause, a programmed state of developmental arrest that enables survival under adverse environmental conditions. In Drosophila melanogaster Meigen, 1830, diapause is characterized by reproductive arrest and reduced intestinal growth, accompanied by suppressed intestinal stem cell (ISC) activity. Juvenile Hormone (JH) promotes ISC proliferation under favorable conditions, but its capacity to modulate stem cell dynamics during cold-induced diapause remains unclear. Here, we investigated whether JH signaling can reactivate midgut remodeling in adult females maintained at 11. At this temperature, flies exhibited pronounced gut atrophy and elevated Phospho-histone H3 (PH3+) cell abundance, consistent with temperature-dependent G2/M phase arrest JH treatment significantly increased the proportion of Delta-positive progenitor cells in the anterior (R2) and posterior (R5) midgut regions at both 11 and 25, demonstrating that JH acts as a conserved mitogen for the ISC pool irrespective of thermal environment. A trend toward reduced PH3+ accumulation in the posterior midgut following JH treatment (p = 0.061) suggests possible facilitation of mitotic exit, though this effect did not reach statistical significance. Despite cellular-level changes, JH treatment did not restore overall gut size, indicating that the 72-84 hour exposure window was insufficient for subsequent tissue hypertrophy. Additionally, we identified a recurrent cold-induced pathology of gut distension, provisionally termed Lumen Obstruction Syndrome (LOS), which was independent of JH signaling. These findings reveal an uncoupling of JH-driven stem cell expansion from gross organ growth under diapause conditions, highlighting the selective sensitivity of the ISC compartment to endocrine signaling during environmental stress.

1Endogenous circadian clocks control circadian rhythms in physiology and behavior. The predominant hypothesis of biological timing suggests that the responsible master clock for all endogenous circadian rhythms is constituted by an evolutionary conserved transcriptional-translational feedback loop (TTFL) clock consisting of positive feedforward and negative feedback elements. Unexpectedly, in contrast to the evolutionary derived insect Drosophila, RNAi-dependent knockdown of any of the negative feedback elements of the core TTFL clock in the basal Madeira cockroach Rhyparobia maderae does not delete circadian rhythms in locomotor activity. Shown here, neither RNAi-dependent triple knockdowns of all three negative feedback elements Period, Timeless 1, and Cryptochrome 2, nor single and double knockdown of the positive elements Clock and Cycle did directly delete circadian locomotor rhythms as mRNA levels declined. Thus, our experimental data do not support the predominant hierarchical hypothesis of circadian timing. To explore alternative mechanisms, we constructed a computational model of a neuronal circadian pacemaker network using planar switching affine systems (PSAS). The PSAS model comprises plasma membrane-associated posttranslational feedback loop (PTFL) clocks that are coupled to the TTFL nuclear clocks. Modeling results aligned with our experimental results. Therefore, both our experimental and modeling data support a systemic hypothesis of biological timing. 3 Significance statementBased mostly upon genetic studies in derived taxa like Drosophila it is hypothesized that circadian timing of behavior is strictly controlled by specific circadian clock neurons in the brain, realized through a transcriptional-translational feedback loop (TTFL) clock. In contrast to this common hierarchical model that requires transcription, we provide evidence in a basal taxon - the Madeira cockroach - for a systemic explanation of circadian timing of behavior that is based on coupled TTFL and posttranslational feedback loop (PTFL) clocks in adaptive neuronal networks.

Bdelloid rotifers are known to survive desiccation and high doses of ionizing radiation. This extreme resistance is notably due to their capacity to cope with numerous DNA double-strand breaks (DSBs). Genes encoding key components of the non-homologous end joining (NHEJ) DNA repair pathway are strongly upregulated in the bdelloid rotifer Adineta vaga following exposure to ionizing radiation. Considering the notably high doses tolerated by these organisms, their capacity to efficiently restore genome integrity is particularly striking. Although NHEJ is generally regarded as less accurate than homologous recombination (HR), the absence of major genomic rearrangements in the descendants of irradiated rotifers suggests that DNA repair occurs with high fidelity. Terwagne et al. recently reported a delayed repair in germline nuclei, occurring during oocyte development when homologous chromosomes pair, thereby enabling template-based repair through HR. In this study, we established an in situ hybridization approach on A. vaga cryosections to investigate the spatial and temporal expression of key actors involved in NHEJ, HR, and Base excision repair (BER) pathways in somatic and germline tissues. We show that NHEJ (KU80) and BER-related genes (PARPs) as well as A. vaga Ligase E (putatively involved in DNA repair) are expressed early after radiation exposure in the somatic syncytium. In contrast, HR-related genes (Rad51: two paralogs, Rad54), as well as PCNA (involved in DNA replication, NER, BER, HR) are expressed later in maturing oocytes, indicating the activation of a delayed homologous recombination repair pathway in germline nuclei. Nurse cells, which express genes associated with both HR and NHEJ pathways, may rely on both mechanisms for their own DNA repair while also supplying mRNAs to the maturing oocyte. Our results provide new evidence for a differential regulation of DNA DSB repair pathways between soma and germline in bdelloids, with NHEJ predominating in somatic tissues and HR in the germline of A. vaga. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=200 SRC="FIGDIR/small/722046v1_ufig1.gif" ALT="Figure 1"> View larger version (35K): org.highwire.dtl.DTLVardef@3b1f3borg.highwire.dtl.DTLVardef@17f5eb5org.highwire.dtl.DTLVardef@122ef14org.highwire.dtl.DTLVardef@7e4413_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOAbstract Figure:C_FLOATNO Summary of in situ hybridization results: genes coding for actors of NHEJ are expressed in the somatic nuclei and in the nurse nuclei of Adineta vaga individuals 2.5 hours post X-rays radiation, while genes coding for HR actors and PCNA (involved in multiple pathways including DNA replication and DNA repair: NER, BER, MR, HR) are expressed in the nurse nuclei 2.5 hours post radiation, and later in the maturing oocyte during oogenesis and in the laid eggs. Genes coding for actors highly expressed post-radiation, involved in the BER pathway appear to be only expressed in the somatic syncytium 2.5 hours post radiation, as well as the gene coding for the Ligase E, likely involved in DNA repair. C_FIG

Most flowering plant species rely on insect pollinators for successful cross-pollination. While floral color, scent, and morphology help attract visitors, the primary motivation for visiting a flower is the nutritional reward - nectar and, especially, pollen. Pollen provides a complete set of macro- and micronutrients essential for adult and larval provisioning in many insect flower visitors. However, pollen nutrient composition (i.e., quality) varies widely among plant species, and different visitors may have distinct nutritional requirements. Whether these differences are linked to the selection of plants visited remains poorly understood. In this study, we investigated whether the nutrient composition of pollen is linked to the visitation patterns of two main alpine pollinator groups: bumblebees and hoverflies. We observed flower visits in the field and identified the origin of pollen collected by bumblebees and hoverflies via metabarcoding. In addition, we analyzed the nutrient profiles of alpine flowering plants from the same habitat, including amino acids, fatty acids, and sterols. We hypothesized that both bumblebees and hoverflies (i) differ in the plant spectrum they were observed on/collected from and visited for pollen collection, (ii) and that preferred nutrient profiles differ between the two pollinator groups. We additionally expected (iii) that, in the studied alpine plant communities, the nutrient composition of pollen of plant species collected by flower visitors is more strongly associated with pollinator identity than with plant phylogeny due to competition for pollinators. Our results revealed that alpine bumblebees and hoverflies were more similar in their pollen hosts and nutritional preferences than expected, but, for both groups, the network based on observed flower visits differed significantly from that based on pollen collection. Pollen fatty acids and amino acids content was positively correlated, and both bumblebees and hoverflies preferred pollen with low fatty and amino acid content. Pollen sterols did not differ between plants collected by pollinators and non-collected plants. Neither fatty acid, amino acid, nor sterol composition was linked to plant phylogeny. Our findings suggest that not only amino acid content, but also fatty acid content, plays a key role in shaping pollen-collection patterns of flower visitors in alpine ecosystems.

Fat accumulation and use is critical for sustaining life. Most insects show a typical response to feeding where fat is accumulated when sufficient sugars and other carbohydrates are consumed. Parasitoid insects are an exception, because most species do not accumulate fat when feeding on a sugar-rich diet. Studies on fat metabolism generally measure fat content early in life without considering lipid metabolism as a dynamic process that is expected to change as life progresses. In this paper, we compared fat accumulation and use throughout the lives of adult female Drosophila melanogaster and females of 5 inbred lines of the parasitoid wasp Leptopilina heterotoma. We expected that fat accumulation would take place irrespective of teneral fat content in D. melanogaster. We found that fat D. melanogaster initially used fat reserves, while lean flies economized on fat stores. Both lean and fat flies started accumulating fat after 7 days of life, indeed showing a typical response for insects. Unlike other parasitoids, L. heterotoma populations differs in fat accumulation patterns that we expected to observe also between inbred lines. In none of the inbred lines, however, did fat accumulation take place. Our results did reveal that inbred lines differed in the rate at which fat was used mainly later during life. We further confirmed that D. melanogaster pupal size was highly correlated with adult female size for both D. melanogaster and L. heterotoma. Overall, our findings for L. heterotoma provide strong evidence that genetic background has a major impact on the rate at which fat is used over a lifetime.

The queen bee is the central individual responsible for colony establishment, growth, and survival. Reliable confirmation of successful mating, continued queen presence, and normal reproductive performance is essential for effective colony management. We present a queen bee detection system based on an array of Hall-effect sensors and a miniature magnetic tag attached to the queen. The system is designed for continuous operation and real-time monitoring. A prototype was developed, constructed, and evaluated under both laboratory and field conditions. Field experiments conducted in an apiary demonstrated that the system can reliably detect queen bee passages through the hive entrance, enabling the identification of activities associated with mating flights. The results confirm the feasibility of Hall-effect sensing for automated, non-invasive queen bee monitoring and establish magnetic sensing as a promising new measurement modality for precision apiculture.

Predator-prey interactions shape the evolution of escape behavior in prey, including different combinations of evasive movements, that may enhance unpredictability in fleeing directions and trajectories. So-called protean motion can enhance survival of flying prey in the wild, but quantifying such behaviors under natural conditions remains challenging. Here we used stereoscopic high-speed videography to record the escape flight behavior of wild males of the butterfly species Morpho menelaus in the Amazonian rainforest, and reconstructed 3D flight trajectories using artificial-neural-network-based tracking. During the experiments, we used a lure to attract freely patrolling male butterflies and elicited escape flights by intercepting their trajectory with a looming insect net swing. We then compared the escape flight kinematics to the pre-attack patrolling behavior. Attacks first induced a rapid upward maneuvering, directly followed by an unpredictable horizontal turn. The following escape flight trajectories showed increased horizontal erraticity and greater intra-individual heading variability, as compared to the pre-attack flight. Surprisingly, the mean speed decreased in the escape phase, notably in the horizontal plane. A significant negative association between horizontal trajectory complexity and flight speed was detected, indicating a speed-erraticity trade-off. These results show that wild Morpho butterflies respond to attacks by combining a climbing maneuver with an unpredictable heading change, followed by a protean escape flight; this increased escape erraticity comes at the expense of reduced escape flight speed. Because these large and relatively slow-flying butterflies display bright iridescent blue coloration on their dorsal wing side, erraticity during flight might enhance the dynamic flash coloration, likely limiting accurate targeting by predators.

Adaptation to local environments enables species to thrive in diverse and challenging habitats. Steep elevational gradients provide a compelling natural adaptation laboratory, because abiotic conditions change progressively over short geographical differences. Given that elevation can strongly reshape physiology and behavior of insects, neuromodulatory systems offer a promising lens through which to examine elevation-specific adaptation. We challenged the hypothesis that adaptation to elevation involves octopaminergic signaling in honey bees (Apis mellifera), an important pollinator species occupying different elevations along East African mountains. We collected foragers from two distinct elevations at Mount Kenya (1,150 m and 1,900 m above sea level) and analyzed elevation-dependent changes in octopaminergic signaling. Tissue-specific analysis revealed a striking upregulation of all three octopamine {beta} receptor genes in the thoracic flight muscles and elevated octopamine brain concentrations at high elevation. Expression differences in the brain and fat body were rather modest. We subjected CRISPR/Cas9-mediated octopamine {beta}2 receptor knockouts to cold stress to study the function of octopaminergic signaling in thermoregulation. Loss of AmOAR{beta}2 reduced both the slope and amplitude of heating phases, indicating altered thermogenic dynamics. Together, these results identify the octopaminergic system as a central neuromodulatory regulator of thermogenic performance across elevations in honey bees. More broadly, our study highlights how modulation of conserved aminergic signaling pathways can shape physiological resilience to environmental gradients, pointing to a general mechanism by which insects adapt to changing thermal landscapes. Highlights- Bees from high and low elevation differ in expression of octopamine {beta} receptor genes and octopamine brain concentrations - CRISPR/Cas9-mediated octopamine receptor knockout alters thermogenic behavior - Octopaminergic signaling emerges as a key neuromodulator in thermal adaptation to elevation in honey bees Significance statementAnimals living along mountain gradients must cope with rapidly changing temperatures, yet the mechanisms enabling this adaptation remain poorly understood. We show that honey bees from higher elevations have increased brain octopamine levels and enhanced expression of octopamine receptors in heat-producing flight muscles. Using gene editing, we demonstrate that disrupting one key receptor alters how bees generate heat under cold stress. These findings identify octopamine signaling as a central regulator of thermogenesis and reveal a mechanism by which insects adjust to colder environments. More broadly, our results highlight how conserved neuromodulatory systems can fine-tune physiological performance, offering insight into how insects may respond to changing climates and expanding environmental extremes.

Many arthropods (insects and crustaceans) rely on their antennular chemosensory system to detect key environmental resources like food. While odor mediated food search is well studied in insects, characterization of crustacean chemosensory behavior has been limited by the long lifespans and large size of traditional crustacean model species. Here, we report the first characterizations of the food search behaviors of the genetically tractable amphipod crustacean, Parhyale hawaiensis. We find that Parhyale can locate an odorous food pellet, and predominantly approach food using direct, targeted swims from the arena walls. Removal of both first and second antennae dramatically reduced foraging success and impaired Parhyales ability to control take-off angle and maintain a stable heading during swims. Removal of the first or second antenna alone did not significantly disrupt foraging, and resulted in mild disruption of orientation phenotypes. Intact animals performed sharp turns near the location of the food pellet, which were observed when either first or second antenna were present, but not when all antennae were removed. Turns were longer and had higher average angular velocities following removal of either set of antennae, with full antenna removals representing the most extreme phenotype. In contrast with the long-held theory that the crustacean second antennae exclusively mediate contact chemosensation, we report that first- and second- antennae both contribute similarly to food localization and stabilization of locomotion in Parhyale in our behavioral paradigm. This work establishes Parhyale as an accessible model for studying olfactory behaviors in an aquatic arthropod.

Gills are multifunctional organs that integrate respiration with homeostasis, including energy demanding processes such as osmoregulation and excretion. In osmoregulating decapod crustaceans, two spatially segregated gill types differ in function, ultrastructure and membrane composition, as well as in their responses to environmental change. Yet mitochondrial function in crab gills remains poorly characterized. Here, for the first time, we used high-resolution respirometry with a substrate-uncoupler-inhibitor titration (SUIT) protocol to characterize the mitochondrial phenotypes in anterior (respiratory) and posterior (osmoregulatory) gills. For this, gill filaments of the shore crab Carcinus maenas were permeabilized for 30 min in a saponin solution (optimized for each tissue at 25 {micro}g or 5 {micro}g saponin {middle dot} mg-1 gill fresh weight for anterior and posterior gills, respectively). Anterior gills exhibited higher leak control ratios (L/P, L/E), consistent with a leak-dominated mitochondrial phenotype that may contribute to redox balance at expense of maximal ATP yield. In contrast, posterior gills, displayed a higher phosphorylation control ratio and tighter coupling (higher Net P), reflecting a tightly-coupled, ATP-producing mitochondrial phenotype, in line with their role in sustaining ATP-intensive activities such as osmoregulation and excretion. Our results revealed that anterior and posterior gills operate as "two engines in one organ": by quantifying how each gill type partitions respiratory capacity between phosphorylation and leak pathways, this study provides a mechanistic framework for understanding how mitochondrial specialization supports functional division of labour within a single organ and contributes to physiological adaptation to dynamically fluctuating marine environments.