nils-herrmann/clean_scirepeval huggingface dataset:
Differential effects of sound level and temporal structure of calls on phonotaxis by female gray treefrogs, Hyla versicolor
Venue: Journal of Comparative Physiology A

We investigated how communication distance influenced the efficacy of communication by studying the effects of two attributes of male chorus sounds, namely, reduction in sound level and degradation of temporal sound structure, on attraction and accuracy of female phonotaxis in gray treefrogs, Hyla versicolor. For this, we conducted acoustic playback experiments, using synthetic calls and natural calls recorded at increasing distances from a focal male as stimuli. We found that the degradation of temporal structure had a greater effect on signal attractiveness than did the reduction in sound level, and that increasing sound level preferentially affected the attractiveness of proximally recorded calls, with less temporal degradation. Unlike signal attraction, accuracy of female localization increased systematically with the sound level. These results suggest that the degradation of temporal fine structure from both the chorus and signal-environmental effects imposes a limit for effective communication distances for female treefrogs in nature.
From ice to ocean: changes in the thermal function of harp seal pelt with ontogeny
Venue: Journal of Comparative Physiology B

Many animals exhibit ontogenetic changes associated with adaptations for survival. Harp seals (Pagophilus groenlandicus) live in the Arctic and rely on thick insulation to maintain thermal homeostasis. Adult harp seals primarily use blubber for insulation, but newborn harp seals rely on a lanugo pelt while nursing, as their blubber layer develops and their first-year pelage grows. This study compared ontogenetic changes in the thermal properties of harp seal pelts in water and in air. Thermal conductivity, pelt thickness, and thermal resistance were measured in water for pelts of harp seal neonates (1 day old), thin whitecoats (4 day old), fat whitecoats (9 day old), ragged jackets (2 week old), beaters (3 week old), and adults and compared to previously published measurements made on the same pelts in air. Pelt conductivity was significantly higher in water than air for pre-molt and molting pups (P ≤ 0.031). Unlike adult pelage, which flattened underwater, lanugo hairs lifted underwater, a phenomenon that has not been reported previously. Thermal resistance of the pelt was significantly reduced in water compared to air for neonates and thin whitecoats (P ≤ 0.0001). A mathematical model of conductive heat transfer for an ellipsoid body showed volume-specific heat loss in water decreased and then stabilized as harp seals aged (P = 0.0321) and was significantly higher for neonates, thin whitecoats, and ragged jackets in water than in air (P ≤ 0.0089). Overall, pelt function is reduced in water for harp seal pups with lanugo, and this renders neonates and thin whitecoats particularly vulnerable to heat loss if submerged.
Motor control pathways in the nervous system of Octopus vulgaris arm
Venue: Journal of Comparative Physiology A

The octopus’s arms have virtually infinite degrees of freedom, providing a unique opportunity for studying movement control in a redundant motor system. Here, we investigated the organization of the connections between the brain and arms through the cerebrobrachial tracts (CBT). To do this, we analyzed the neuronal activity associated with the contraction of a small muscle strand left connected at the middle of a long isolated CBT. Both electrical activity in the CBT and muscle contraction could be induced at low threshold values irrespective of stimulus direction and distance from the muscle strand. This suggests that axons associated with transmitting motor commands run along the CBT and innervate a large pool of motor neurons en passant. This type of innervation implies that central and peripheral motor commands involve the simultaneous recruitment of large groups of motor neurons along the arm as required, for example, in arm stiffening, and that the site of movement initiation along the arm may be determined through a unique interplay between global central commands and local sensory signals.
Stingless bees and their adaptations to extreme environments
Venue: Journal of Comparative Physiology A

Nearly half of all terrestrial tropical ecosystems around the globe comprise dry forests, characterised through elevated temperatures all year round, and short rainy seasons at irregular intervals. The consequent water deficit over several consecutive months limits the availability of floral resources to often very brief and unpredictable periods, which poses a challenge to the maintenance of perennial colonies in highly eusocial bees. Thus, only few highly eusocial bees occur permanently in tropical dry forests, among them some highly adapted species of stingless bees (Apidae, Meliponini). In the present review, we discuss the current knowledge on the adaptations to such extreme environments in Melipona subnitida, a stingless bee native to the Brazilian tropical dry forest. Key to the success of this species is not so much heat resistance of foragers, as it is the ability to maintain perennial colonies despite extended dearth periods. After several months of drought, M. subnitida colonies are capable of re-establishing fully functional colonies from nests containing only few dozens of workers. This surprising resilience is based on a quick reaction to precipitation-driven increase in floral resource availability, mainly owing to selective foraging at high-profit resources and an immediate up-regulation of brood production once food storage conditions improve.
Evoked potential study of the inferior collicular response to constant frequency-frequency modulation (CF-FM) sounds in FM and CF-FM bats
Venue: Journal of Comparative Physiology A

The auditory system of echolocating bats is adapted for processing species-specific ultrasonic signals. While FM (frequency modulation) bats are strictly sensitive to the frequency ranges of their orientation signals or prey-generated noise, CF-FM (constant frequency-FM) bats have a disproportionate number of neurons tuned to frequencies near the CF component of their orientation sounds, and most of them are on–off responders. Furthermore, the inferior collicular neurons of the CF-FM bats discharged as single-on or double-on responders to CF-FM stimuli. To further study the differences in auditory signal processing of these two types of bats, as the first step we conducted an evoked potential response study in the inferior colliculus of the CF-FM bat, Hipposideros pratti and the FM bat, Pipistrellus abramus using CF, FM and CF-FM stimuli. The results showed that the CF sounds always evoked collicular on- and off-responses in CF-FM bats, but the FM bats only had on-responses to both CF and FM sounds, indicting species-specific neural circuits. However, when stimulated with CF-FM sounds, collicular responses were evoked by both the CF and FM components from both FM and CF-FM bats, suggesting they have some generic neural circuit.
Fuelling on the wing: sensory ecology of hawkmoth foraging
Venue: Journal of Comparative Physiology A

Hawkmoths (Lepidoptera, Sphingidae) comprise around 1500 species, most of which forage on nectar from flowers in their adult stage, usually while hovering in front of the flower. The majority of species have a nocturnal lifestyle and are important nocturnal pollinators, but some species have turned to a diurnal lifestyle. Hawkmoths use visual and olfactory cues including CO2 and humidity to detect and recognise rewarding flowers; they find the nectary in the flowers by means of mechanoreceptors on the proboscis and vision, evaluate it with gustatory receptors on the proboscis, and control their hovering flight position using antennal mechanoreception and vision. Here, we review what is presently known about the sensory organs and sensory-guided behaviour that control feeding behaviour of this fascinating pollinator taxon. We also suggest that more experiments on hawkmoth behaviour in natural settings are needed to fully appreciate their sensory capabilities.
An intertidal fish shows thermal acclimation despite living in a rapidly fluctuating environment
Venue: Journal of Comparative Physiology B

The co-evolution of acclimation capacity and thermal performance breadth has been a contentious issue for decades, and little is known regarding the extent to which acclimation alters the shape of acute thermal performance curves. Current acclimation theory suggests that when daily variation is large and unpredictable ectotherms should not acclimate but should evolve wide performance breadths, allowing maintenance of performance across a wide thermal range. The subtropical intertidal zone, however, experiences a large amount of daily thermal variation, but daily means and ranges shift in predictable ways with season, where daily and seasonal variation is roughly equal. We predicted that animals in this habitat would maintain their capacity to acclimate and that performance breadth would not be altered by acclimation to maintain function with rapidly fluctuating daily temperatures. We tested our prediction using a subtropical goby, Bathygobius cocosensis, which lives in tide pools that vary widely, over days and seasons. We exposed B. cocosensis to winter (12−17 °C) and summer (30−35 °C) thermal conditions for six weeks and then measured the thermal dependence of burst swimming speed, routine and maximum metabolic rate, and ventilation rate between 12 and 36 °C. B. cocosensis exhibited an acclimation response for burst swimming speed, maximum metabolic rate and metabolic scope, but acclimation did not alter the shape of acute thermal performance curves. These results indicate that thermal acclimation can occur when short-term thermal variability is large and equal to seasonal variation, and wide performance breadths can be maintained with acclimation in heterogeneous environments.
Moult-related reduction of aerobic scope in passerine birds
Venue: Journal of Comparative Physiology B

It is well established that the nutrient and energy requirements of birds increase substantially during moult, but it is not known if these increased demands affect their aerobic capacity. We quantified the absolute aerobic scope of house and Spanish sparrows, Passer domesticus and P. hispaniolensis, respectively, before and during sequential stages of their moult period. The absolute aerobic scope (AAS) is the difference between maximum metabolic rate (MMR) during peak locomotor activities and minimum resting metabolic rate (RMRmin), thus representing the amount of aerobic power above that committed to maintenance needs available for other activities. As expected, RMRmin increased over the moult period by up to 40 and 63% in house and Spanish sparrows, respectively. Surprisingly, the maximum metabolic rates also decreased during moult in both species, declining as much as 25 and 38% compared with pre-moult values of house and Spanish sparrows, respectively. The concurrent changes in RMRmin and MMR during moult resulted in significant decreases in AAS, being up to 32 and 47% lower than pre-moult levels of house and Spanish sparrows, respectively, during moult stages having substantial feather replacement. We argue that the combination of reduced flight efficiency due to loss of wing feathers and reduced aerobic capacity places moulting birds at greater risk of predation. Such performance constraints likely contribute to most birds temporally separating moult from annual events requiring peak physiological capacity such as breeding and migration.
Bumblebees are able to perceive amino acids via chemotactile antennal stimulation
Venue: Journal of Comparative Physiology A

Like all animals, bees need to consume essential amino acids to maintain their body’s protein synthesis. Perception and discrimination of amino acids are, however, still poorly understood in bees (and insects in general). We used chemotactile conditioning of the proboscis extension response (PER) to examine (1) whether Bombus terrestris workers are able to perceive amino acids by means of their antennae and (if so) which ones, (2) whether they are able to differentiate between different amino acids, and (3) whether they are able to differentiate between different concentrations of the same amino acid. We found that workers perceived asparagine, cysteine, hydroxyproline, glutamic acid, lysine, phenylalanine, and serine, but not alanine, leucine, proline, or valine by means of their antennae. Surprisingly, they were unable to differentiate between different (perceivable) amino acids, but they distinguished between different concentrations of lysine. Consequently, bumblebees seem to possess amino acid receptors at the tip of their antennae, which enable a general perception of those solute amino acids that have an additional functional group (besides the common amino and carboxylic groups). They may thus have the ability to assess the overall amino acid content of pollen and nectar prior to ingestion.
Flower scent of Ceropegia stenantha: electrophysiological activity and synthesis of novel components
Venue: Journal of Comparative Physiology A

In specialized pollination systems, floral scents are crucial for flower–pollinator communication, but key volatiles that attract pollinators are unknown for most systems. Deceptive Ceropegia trap flowers are famous for their elaborate mechanisms to trap flies. Recent studies revealed species-specific floral chemistry suggesting highly specialized mimicry strategies. However, volatiles involved in fly attraction were until now identified in C. dolichophylla and C. sandersonii, only. We here present data on C. stenantha for which flower scent and pollinators were recently described, but volatiles involved in flower–fly communication stayed unknown. We performed electrophysiological measurements with scatopsid fly pollinators (Coboldia fuscipes) and identified 12 out of 13 biologically active floral components. Among these volatiles some were never described from any organism but C. stenantha. We synthesized these components, tested them on antennae of male and female flies, and confirmed their biological activity. Overall, our data show that half of the volatiles emitted from C. stenantha flowers are perceived by male and female fly pollinators and are potentially important for flower–fly communication in this pollination system. Further studies are needed to clarify the role of the electrophysiologically active components in the life of scatopsid fly pollinators, and to fully understand the pollination strategy of C. stenantha.
Cross-modal transfer in visual and nonvisual cues in bumblebees
Venue: Journal of Comparative Physiology A

Bumblebees Bombus terrestris are good at learning to distinguish between patterned flowers. They can differentiate between flowers that differ only in their patterning of scent, surface texture, temperature, or electrostatic charge, in addition to visual patterns. As recently shown, bumblebees trained to discriminate between nonvisual scent patterns can transfer this learning to visually patterned flowers that show similar spatial patterning to the learnt scent patterns. Bumblebees can, therefore, transfer learnt patterns between different sensory modalities, without needing to relearn them. We used differential conditioning techniques to explore whether cross-modal transfer of learnt patterns also occurred between visual and temperature patterns. Bumblebees that successfully learnt to distinguish rewarding and unrewarding temperature patterns did not show any preferences for the corresponding unlearnt visual pattern. Similarly, bumblebees that learnt visual patterns did not transfer these to temperature patterns, suggesting that they are unable to transfer learning of temperature and visual patterns. We discuss how cross-modality pattern learning may be limited to modalities that have potentially strong neurological links, such as the previously demonstrated transfer between scent and visual patterns.
Effect of the algal alkaloid caulerpin on neuropeptide Y (NPY) expression in the central nervous system (CNS) of Diplodus sargus
Venue: Journal of Comparative Physiology A

Recent studies have suggested that Mediterranean indigenous fish species are affected by bioactive metabolites coming from marine invasive species via food web interactions. In particular, both physiological and behavioural changes in the white sea bream Diplodus sargus were related to caulerpin (CAU), a bisindolic alkaloid particularly abundant in the invasive alga Caulerpa cylindracea, on which the fish actively feed. Dietary administration of CAU decreased aggressiveness in D. sargus, suggesting an anxiolytic-like effect of CAU possibly mediated by endogenous anxiolytic agents. This hypothesis is supported here by the finding of a significant increase of NPY transcriptional expression in the brain of fish fed with CAU enriched food, shedding more light on the neural mechanisms behind the altered behaviour of D. sargus.
Antioxidant capacity is repeatable across years but does not consistently correlate with a marker of peroxidation in a free-living passerine bird
Venue: Journal of Comparative Physiology B

Oxidative stress occurs when reactive oxygen species (ROS) exceed antioxidant defences, which can have deleterious effects on cell function, health and survival. Therefore, organisms are expected to finely regulate pro-oxidant and antioxidant processes. ROS are mainly produced through aerobic metabolism and vary in response to changes in energetic requirements, whereas antioxidants may be enhanced, depleted or show no changes in response to changes in ROS levels. We investigated the repeatability, within-individual variation and correlation across different conditions of two plasmatic markers of the oxidative balance in 1108 samples from 635 free-living adult collared flycatchers (Ficedula albicollis). We sought to manipulate energy constraints by increasing wing load in 2012 and 2013 and by providing additional food in 2014. We then tested the relative importance of within- and between-individual variation on reactive oxygen metabolites (ROMs), a marker of lipid and protein peroxidation, and on non-enzymatic antioxidant defences (OXY test). We also investigated whether the experimental treatments modified the correlation between markers. Antioxidant defences were repeatable (range of repeatability estimates = 0.128–0.581), whereas ROMs were not (0–0.061). Antioxidants varied neither between incubation and nestling feeding nor between sexes. ROMs increased from incubation to nestling feeding in females and were higher in females than males. Antioxidant defences and ROM concentration were globally positively correlated, but the correlation varied between experimental conditions and between years. Hence, the management of oxidative balance in wild animals appears flexible under variable environmental conditions, an observation which should be confirmed over a wider range of markers.
Foraging strategies and physiological adaptations in large carpenter bees
Venue: Journal of Comparative Physiology A

Large carpenter bees are charismatic and ubiquitous flower visitors in the tropics and sub-tropics. Unlike honeybees and bumblebees that have been popular subjects of extensive studies on their neuroethology, behaviour and ecology, carpenter bees have received little attention. This review integrates what is known about their foraging behaviour as well as sensory, physiological and cognitive adaptations and is motivated by their versatility as flower visitors and pollinators. This is evident from their extremely generalist foraging and adeptness at handling diverse flower types as legitimate pollinators and as illegitimate nectar robbers. They purportedly use traplining to forage between isolated patches and are long-distance flyers over several kilometres suggesting well-developed spatial learning, route memory and navigational capabilities. They have a broad range of temperature tolerance and thermoregulatory capabilities which are likely employed in their forays into crepuscular and nocturnal time periods. Such temporal extensions into dim-light periods invoke a suite of visual adaptations in their apposition optics. Thus, we propose that carpenter bees are an excellent though understudied group for exploring the complex nature of plant-pollinator mutualisms from ecological and mechanistic perspectives.
Eye and wing structure closely reflects the visual ecology of dung beetles
Venue: Journal of Comparative Physiology A

An important resource partitioning strategy allowing dung beetles to coexist in the same habitat, while utilising the same food, is species’ separation of activity times. After establishing the diel activity period of three closely related, co-occurring dung beetles, we examined their eye and wing morphology. Absolute and relative eye size, and facet size were greater in the nocturnal Escarabaeus satyrus, followed by the crepuscular Scarabaeus zambesianus and then the diurnal Kheper lamarcki. The diurnal K. lamarcki had the highest wing aspect ratio (long, narrow wings), followed by the crepuscular S. zambesianus and the nocturnal E. satyrus (short, broad wings), suggesting that dim-light active species fly slower than diurnal species. In addition, the two species active in dim light had a lower wing loading than the diurnal species, indicating the need for greater manoeuvrability in the dark. Analyses of wing shape revealed that the diurnal K. lamarcki wing had a proportionally larger jugal and anal region than both dim light species. Our results show that different species of dung beetles have a combination of optical and morphological wing adaptations to support their foraging activities in diverse light conditions.
A high-fat diet impacts memory and gene expression of the head in mated female Drosophila melanogaster
Venue: Journal of Comparative Physiology B

Obesity predisposes humans to a range of life-threatening comorbidities, including type 2 diabetes and cardiovascular disease. Obesity also aggravates neural pathologies, such as Alzheimer’s disease, but this class of comorbidity is less understood. When Drosophila melanogaster (flies) are exposed to high-fat diet (HFD) by supplementing a standard medium with coconut oil, they adopt an obese phenotype of decreased lifespan, increased triglyceride storage, and hindered climbing ability. The latter development has been previously regarded as a potential indicator of neurological decline in fly models of neurodegenerative disease. Our objective was to establish the obesity phenotype in Drosophila and identify a potential correlation, if any, between obesity and neurological decline through behavioral assays and gene expression microarray. We found that mated female w1118 flies exposed to HFD maintained an obese phenotype throughout adult life starting at 7 days, evidenced by increased triglyceride stores, diminished life span, and impeded climbing ability. While climbing ability worsened cumulatively between 7 and 14 days of exposure to HFD, there was no corresponding alteration in triglyceride content. Microarray analysis of the mated female w1118 fly head revealed HFD-induced changes in expression of genes with functions in memory, metabolism, olfaction, mitosis, cell signaling, and motor function. Meanwhile, an Aversive Phototaxis Suppression assay in mated female flies indicated reduced ability to recall an entrained memory 6 h after training. Overall, our results support the suitability of mated female flies for examining connections between diet-induced obesity and nervous or neurobehavioral pathology, and provide many directions for further investigation.