Biology subjects

De Agro, M.

Publications and source records attributed to De Agro, M..

15 recordsLinked to original sources

bioRxiv2026

ctSpyderFields: A Python package for visual field reconstruction in spiders

1The measurement of visual fields in arachnology has a long-standing history. Given the wide variety of eye positions, orientation and structure, the topic is fundamental for studies of taxonomy, evolution, ecology and behavior. The existing methods for measuring visual fields deploy ophthalmoscopic measurements, which require custom microscopes, anatomical structures like the reflective tapetum, which may not always be present, or the capacity to detect photoreceptor autofluorescence. Here we present the ctSpyderFields python package: a tool for geometrically predicting the visual fields of arachnids from digital images of the lens and retina. The tool uses images coming from computed tomography (CT) scans of specimens, but could be applied to other 3D microscopy techniques, to virtually project the boundaries of the retina through the geometrically predicted nodal point of the lens, deriving a rough per-eye visual field both in cartesian and spherical coordinates. The extracted data can then be used to calculate likely visual field overlap between eyes and angular spans, which can be compared within or between species. We also provide a use case, reporting the visual field data extracted from a museum specimen of Philaeus crysops. We propose that the tool will allow a wider comparative analysis of visual fields across spider species, unlocking the potential for a deeper understanding of visual ecology and evolution.

bioinformatics↗

bioRxiv2026

Visual detection of cryptic displays in jumping spiders

Most animals can segment camouflaged targets via static cues, such as luminance or contrast differences against a background. However, targets can be cryptic and merge with background clutter, making static cues unavailable until the camouflaged object starts moving: the target can then be segmented by identifying spatially coherent luminance changes over time. Jumping spiders represent a unique model for the study of spatiotemporal segmentation, as they process moving signals and static figures separately through distinct pathways associated with different pairs of eyes: the secondary eyes detect moving objects and trigger full body pivot responses, bringing the target within focused view of the principal eyes for subsequent figure processing. While secondary eyes can be selective for specific stimulus characteristics that cause the animal to pivot, it remains unclear whether their selectivity requires full motion segmentation or relies on simpler stimulus characteristics. Here, we tested whether the pivoting response triggered by secondary eyes is specifically linked to motion segmentation, or whether it is also elicited by less specific stimulus characteristics. We presented jumping spiders with several moving and non-moving stimuli, including clearly delineated objects, cryptic objects visible only through motion, and non-segmentable spatio-temporal luminance patterns. Based on the measured responses, we developed a computational model that captured all salient features of the pivoting behavior produced by the animal. We found that jumping spiders do not require a discrete, segmented object to trigger a pivoting response. Instead, they attend to luminance patterns that change across both time and space, while disregarding changes that repeat over the same spatial location. This mechanism constitutes an effective solution in terms of neural simplification: it offloads the task of complex motion segmentation from the secondary eyes, thus maximizing the efficiency of visual modularity--a unique evolutionary solution to the problem of brain miniaturization.

neuroscience↗

bioRxiv2025

Antlion larvae follow optimality rules in body orientation during sand-tossing

Pit-building antlion larvae (Myrmeleon spp.) throw sand at prey that approach their pit using their head and mandibles as a backward-directed "biological catapult". This mechanism restricts effective sand-tossing to a defined angular range behind the larva. When prey-like vibrations come from outside this range, antlions are known to reorient, but the consistency and rules behind this behaviour remain unclear. We tested whether larvae follow optimal turning strategies when reorienting toward a vibrating artificial stimulus placed in disadvantageous positions along the pit. Most larvae responded and often ended in an optimal sand-throwing position. Initial orientation strongly predicted turning direction: larvae rotated along the shortest angular path to reach the optimal sand-throwing orientation. Our results show that antlion larvae do not rely on rigid reflexes during prey capture but appear to integrate vibrational cues with spatial rules to minimize angular displacement. This reveals unexpected behavioural flexibility in a sit-and-wait predator with highly limited mobility.

animal behavior and cognition↗

bioRxiv2025

Biological point-light displays scanning by the principal eyes of a jumping spider

The semi-rigid structure of bodies forces mobile animals to move in rhythmic patterns shared by all creatures with skeletons, exoskeletons, or limb connections. This pattern, known as biological motion, is instantly recognizable and conveys "animacy," even when body shape is removed and only a cloud of moving dots is shown. Indeed, motion alone is so informative that some animals can infer the original shape based on the dots concurrent activity. Jumping spiders, highly visual arthropods, divide motion detection and shape recognition between their four pairs of eyes. Previous studies found that they can distinguish biological from non-biological motion using only their motion-detecting anterior lateral eyes yet seemed unable to extract shape from motion. In this study, we examined how the anterior medial eyes of jumping spiders--which are used for shape recognition--respond to dot clouds depicting biological or non-biological motion. Using a custom eye tracker, we monitored retinal movements during presentation of static and moving stimuli. We found spiders change their retinal shifting pattern based on both the targets motion (biological or not) and implied structure (i.e., whether dots suggest a coherent shape). These results reveal that jumping spiders analyze motion with more complexity than previously thought, suggesting a deeper integration of motion and form processing within their minuscule, modular brains.

animal behavior and cognition↗

bioRxiv2024

Jumping spiders are not fooled by the peripheral drift illusion

In the peripheral drift illusion, a static circular sawtooth pattern is perceived as if it were rotating. It is believed that this effect is a byproduct of how the neural substrate responsible for motion perception is organized. The structure of the motion perception circuitry is widespread across the animal kingdom, vertebrates and invertebrates alike, which in turn causes the illusion effect to be experienced by virtually all animals. Among invertebrates, jumping spiders possess a unique visual system. For them, the tasks of visual computation are split across 4 pairs of eyes, with motion detection, target recognition, and shape discrimination computed in completely segregated brain areas and visual field sections. In such an organization, it is unlikely that the circuitry for motion perception common to other animals is shared by jumping spiders. Consequently, jumping spiders should be immune to the peripheral drift illusion. To test this hypothesis, we placed jumping spiders on top of an omnidirectional treadmill and presented them with circular visual stimuli in their visual periphery. These were either composed of a sawtooth pattern, and therefore inducing the illusion, or of a sine-wave pattern of equal luminance and spatial frequency but not illusion-inducing. The stimuli could either be static or rotate around their center, either clockwise or counterclockwise. As jumping spiders perform distinctive full-body pivots when detecting a moving object in their visual periphery, we registered the frequency of this behavior to assess the illusory percept. We found that the spiders responded consistently to all moving stimuli, but did not react to the static illusion, therefore it was not perceived as in motion. The absence of the illusory percept in spiders opens many questions about the nature of their motion perception circuitry and casts doubts on how the illusion is widespread in the animal kingdom outside the common model species usually inquired about.

animal behavior and cognition↗

bioRxiv2024

Three-dimensional body reconstruction enables quantification of liquid consumption in small invertebrates

Quantifying feeding patterns provides valuable insights into animal behaviour. However, small invertebrates often consume incredibly small amounts of food. This renders traditional methods, such as weighing individuals before and after food acquisition, either inaccurate or prohibitively expensive. Here, we present a non-invasive method to quantify food consumption of small invertebrates whose body expands during feeding. Using the markerless pose estimation software DeepLabCut, we three-dimensionally track the body of Argentine ants, Linepithema humile. Using these extracted markers, we developed an algorithm which computationally reconstructs the ants body, directly measuring volumetric change over time. Moreover, we provide measures of accuracy and quantify the ants feeding response to a range of sucrose concentrations, as well as a gradient of caffeine-laced sucrose solutions. Small invertebrates are often prolific invasive species and disease vectors, causing significant ecological and economical damage. Understanding their feeding behaviour could be an important step towards effective control strategies.

animal behavior and cognition↗

bioRxiv2023

Acute exposure to caffeine improves navigation in an invasive ant

Invasive alien species are a major and growing problem, devastating ecosystems and costing billions of euros in damage and control efforts. Argentine ants, Linepithema humile, are particularly concerning, with control efforts often falling short likely due to a lack of sufficient bait consumption. Using neuroactives to manipulate ant navigation and learning could increase recruitment and consumption, ultimately leading to more efficient control strategies. Caffeine is naturally occurring, cheap, and has been found to cause motivational and cognitive improvements in bees. Here, we subject L. humile to a wide range of caffeine concentrations and a complex but ecologically relevant task: an open landscape foraging experiment. Without caffeine, we find no effect of consecutive foraging visits on the time the ants take to reach a reward, suggesting a failure to learn the rewards location. However, low (25ppm) to intermediate (250ppm) concentrations of caffeine lead to a decrease of up to 38% in the time taken to find the reward during each consecutive visit, implying that caffeine boosts learning. Interestingly, such improvements are lost at high (2000ppm) doses. In contrast, caffeine appears to have no impact on the ants homing behaviour, as the time required to reach the nest was similar across treatments. The effect of caffeine is thus not only dose-dependent, but also differentially targets neurologically distinct navigational mechanisms. Adding moderate levels of caffeine to baits could be a simple way to improve ants ability to learn its location, potentially leading to increased recruitment to, and consumption of, the toxicant.

animal behavior and cognition↗

bioRxiv2023

Eye-specific detection and a multi-eye integration model of biological motion perception

The term biological motion refers to the peculiar kinematics of living organisms. Their interconnected joints move at a fixed distance from each other, a pattern that is common among all locomotive, rigid animals. Across the animal kingdom, many species have developed specialized circuitry to visually recognize biologically moving stimuli and discriminate them from other patterns. Recently, this skill has also been observed in the distributed visual system of jumping spiders. These eight-eyed animals use three of their eye pairs to perceive motion. Then, the gaze of the remaining pair is shifted towards the detected object for further inspection. When presented with a biologically moving stimulus and a random one, jumping spiders turn to face the latter, demonstrating discrimination. In the current paper, we systematically tested the ability of jumping spiders to discriminate biological from random displays using every single eye-pair, by blocking the others with paint. The animals were able to discriminate the stimuli only when the anterior-lateral eyes were unblocked, performing at chance level with the other pairs. Crucially, the spiders preferred the biological stimulus, not the random one. To explain this preference reversal we hypothesized a model, describing how the anterior-lateral eyes specialization in detecting biological motion feeds into a multi-eye integration system, generating more complex behavior from the combination of the simple, single-eye responses. We propose that this in-built modularity may be a solution to the limited resources of these invertebrates brains, constituting a novel approach to visual processing.

animal behavior and cognition↗

bioRxiv2023

Habituation to visual stimuli is personality-independent in a jumping spider

1Jumping spiders display some of the richest visually-mediated behaviors in nature. Vision is indeed the most important sensory modality in these spiders where motion detection and response to visual stimuli allow key behaviors such as hunting, escaping from predators, and mating. These spiders have been used in various experiments demonstrating the existence of good associative learning and memory abilities, whose mechanism parallels that found in vertebrates. Here we focused on the habituation and dis-habituation (H/DH) paradigm, indicating either a gradual decrease in responsiveness to repeated visual stimuli (H), or a recovery of the habituated stimulus (DH). H is an elementary form of non-associative learning and memory, which is expected to vary from individual to individual. The link between personality and H/DH has been shown in many vertebrates, but rarely in invertebrates. To tackle this question we tested whether personality affects H/DH in the jumping spider Menemerus semilimbatus. In our protocol, habituation was assessed by presenting repeatedly a visual stimulus on a screen to spiders tethered on a locomotor compensator. In the same individuals, personality (namely boldness) was assessed in a walking arena equipped with a shelter. We found that M. semilimbatus habituated and dishabituated to our visual stimulus and that they differed in personality along a shy-bold axis. However, contrary to our expectations, personality was not related to learning. We discussed the results and speculated that the nature (neutral value) of the stimulus might have played a role in making learning independent from personality.

animal behavior and cognition↗

bioRxiv2023

Study replication: Shape discrimination in a conditioning procedure on the jumping spider Phidippus regius

Jumping spiders possess a unique visual system, split into 8 different eyes and divided into two fully independent visual pathways. This peculiar organization begs the question of how visual information is processed, and whether the classically recognized gestalt rules of perception hold true. In a previous experiment, we tested the ability of jumping spiders to associate a geometrical shape with a reward (sucrose solution), and then to generalize the learned association to a partially occluded version of it. The occluded shape was presented together with a broken version of the same shape. The former should be perceived as a whole shape only in the case the animals, like humans, are able of amodally complete an object partly hidden by an occluder; otherwise, the two shapes would be perceived as identical. There, the spiders learned the association but failed to generalize. Here, we present a replication of the experiment, with an increased number of subjects, a DeepLabCut-based scoring procedure, and an improved statistical analysis. The results of the experiment follow closely the direction of the effects observed in the previous work but fail to raise to significance. We discuss the importance of study replication, and we especially highlight the use of automated scoring procedures to maximize objectivity in behavioural studies.

animal behavior and cognition↗

bioRxiv2023

Separate attentional processes in the two visual systems of jumping spiders

1By selectively focusing on a specific portion of the environment, animals can solve the problem of information overload, toning down irrelevant inputs and concentrate only on the relevant ones. This may be of particular relevance for animals such as the jumping spider, which possess a wide visual field of almost 360{degrees} and thus could benefit from a low-cost system for sharpening attention. Jumping spiders have a modular visual system composed of four pairs of eyes, of which only the two frontal eyes (i.e., AMEs) are motile, whereas the other secondary pairs remain immobile. We hypothesized that jumping spiders can exploit both primary and secondary eyes for stimulus detection and attentional shift, with the two systems working synergistically. In Experiment 1 we investigated AMEs attentional responses following a spatial cue presented to the secondary eyes. In Experiment 2, we tested for enhanced attention in the secondary eyes visual field congruent with the direction of the AMEs focus. In both experiments, we observed that animals were faster and more accurate in detecting a target when it appeared in a direction opposite to that of the initial cue. In contrast with our initial hypothesis, these results would suggest that attention is segregated across eyes, while each system works to compensate the other by attending to different spatial locations, rather than sharing a common attentional focus.

animal behavior and cognition↗

bioRxiv2022

Bundling and segregation affects "liking", but not "wanting", in an insect

Behavioural economists have identified many psychological manipulations which affect perceived value, although value in humans is not a unitary experience, with "liking" and "wanting" being neurologically separate processes. A prominent example of this is bundling, in which several small gains (or costs) are experienced as more valuable (or costly) than if the same total amount is presented together. While extensively demonstrated in humans, to our knowledge this effect has never been investigated in an animal, let alone an invertebrate. We trained individual Lasius niger workers to two of three conditions in which either costs (travel distance), gains (sucrose reward), or both were either bundled or segregated: A) both costs and gains bundled, B) both segregated, and C) only gains segregated. We recorded pheromone deposition on the ants return trips to the nest as measure of "liking". After training, we offer the ants a binary choice between odours associated with the treatments, as a measure of "wanting". While bundling treatment did not affect choice, i.e. "wanting", it strongly influenced pheromone deposition, i.e. "liking". Ants deposited c. 80% more pheromone when rewards were segregated but costs bundled as compared with both costs and rewards being bundled. This pattern is further complicated by the pairwise experience each animal made, and which of the treatments it experiences first during training. The current study is the first to demonstrate a bundling effect in an animal, and the first to report a dichotomy between "liking" and "wanting" in an insect. We propose that the deviation between "wanting" and "liking" in this case is due to the unique nature of distance perception in ants, which is recorded linearly, while almost all other sensory perception in animals is logarithmic.

ecology↗

bioRxiv2022

Bees differentiate sucrose solution from water at a distance

Bees are perhaps the most important model for studying complex cognition in invertebrates, showing a variety of impressive abilities. Many experiments employ a training procedure in which the animal associates a characteristic of a "flower" (neutral stimulus) to sucrose solution (positive stimulus) over multiple foraging bouts. We hypothesized that sucrose solution might appear different from water to the bee sensorium, rendering it superfluous for the animal to learn the intended experimental cues. To test this hypothesis, we presented bumblebees simultaneously with 1.6M sucrose and water on artificial flowers. We presented the solutions in three conditions, to identify the most likely recognition mechanism: in drop form, inside cotton-plugged centrifuge tubes, and soaked into raised cigarette filters. The bumblebees chose to contact the sucrose solution significantly more often in all three conditions, confirming their ability to discriminate sucrose from water at a distance, with spectral differences being the most likely mechanism for this differentiation. These results have large implications for the design of training procedures, as the presence of an alternative cue may mask the learning of challenging tasks. This may force us to re-examine much of the literature and unpublished negative results on bee cognition: weakening some claims, but strengthening others.

animal behavior and cognition↗

bioRxiv2021

Young chicks rely on perceptual grouping to discriminate prime numbers

Grouping sets of elements into smaller, equal-sized, subsets constitutes a perceptual strategy employed by humans and other animals to enhance cognitive performance. We hypothesized that asymmetrical grouping, a characteristic of prime numbers, could provide visual cues enabling discrimination of prime from non-prime numerosities. Newborn chicks were habituated to even numerosities (as sets of elements presented on a screen), and then tested for their spontaneous choice among a prime and a non-prime odd numerosity. Chicks discriminated and preferred the prime over the composite set of elements. We discuss this result in terms of novelty preference. By employing different contrasts (i.e., 7vs.9, 11vs.9, and 13vs.15) we investigated the limits of such mechanism showing that induced grouping positively affects chicks performance.

animal behavior and cognition↗

bioRxiv2019

Irrational risk aversion in ants is driven by perceptual mechanisms

Animals must often decide between exploiting safe options or risky options with a chance for large gains. While traditional optimal foraging theories assume rational energy maximisation, they fail to fully describe animal behaviour. A logarithmic rather than linear perception of stimuli may shape preference, causing animals to make suboptimal choices. Budget-based rules have also been used to explain risk-preference, and the relative importance of these theories is debated. Eusocial insects represent a special case of risk sensitivity, as they must often make collective decisions based on resource evaluations from many individuals. Previously, colonies of the ant Lasius niger were found to be risk-neutral, but the risk preference of individual foragers was unknown. Here, we tested individual L. niger in a risk sensitivity paradigm. Ants were trained to associate a scent with 0.55M sucrose solution and another scent with an equal chance of either 0.1 and 1.0M sucrose. Preference was tested in a Y-maze. Ants were extremely risk averse, with 91% choosing the safe option. Even when the risky option offered on average more sucrose (0.8M) than the fixed option, 75% preferred the latter. Based on the psychophysical Weber-Fechner law, we predicted that logarithmically balanced alternatives (0.3M vs 0.1M/0.9M) would be perceived as having equal value. Our prediction was supported, with ants having no preference for either feeder (53% chose the fixed option). Our results thus strongly support perceptual mechanisms driving risk-aversion in ants, and demonstrate that the behaviour of individual foragers can be a very poor predictor of colony-level behaviour.

animal behavior and cognition↗