Biology subjects

Currea, J. P.

Publications and source records attributed to Currea, J. P..

6 recordsLinked to original sources

bioRxiv2026

Superposition eyes of diurnal and nocturnal hawkmoths are imperfect spheres and lack acute zones.

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.

animal behavior and cognition↗

bioRxiv2026

Odor tracking in flying Drosophila requires visual reafference and compass neurons

Flying Drosophila critically depend on high-contrast visual surroundings to localize odor sources in still air, yet the neural mechanisms of visual integration for active odor tracking are unknown. We demonstrate that E-PG neurons--head direction cells in the central complex--work in concert with self-generated visual motion signals to maintain a stable heading metric during olfactory navigation in flight. Using a magnetic tether system and a digital "visual clamp", we show that removing the visual feedback generated by a flys own turns (reafference) causes the animal to lose its heading within an odor plume. Thus, olfactory and mechanosensory signals alone are insufficient for plume stabilization. E-PG neurons have been shown to store visual changes in heading during flight. Genetically hyperpolarizing E-PG neurons significantly compromised the flies ability to both acquire and maintain heading toward a food odor. Notably, silencing these neurons did not disrupt basic visual reflexes, such as optomotor gaze stabilization or object tracking, indicating a specific role in odor-directed visual navigation rather than basic visual flight control. While odor was found to modulate the frequency and amplitude of turns independently, E-PG neurons are essential for directing the orientation of corrective saccades toward the plume center. These results establish that visual reafference engages the internal visual compass to sustain a spatial working memory of heading changes between saccades, allowing flies to maintain a straight course and navigate effectively toward an invisible odor source in flight. Significance StatementA crucial brain function that remains largely mysterious is building robust working memory by integrating stimuli across sensory modalities. For flying Drosophila, visual feedback is required to localize an odor source. Recently, a group of cells residing in the navigation center of the fly brain (E-PG neurons) have been shown to function like an internal compass, providing a dynamic working memory of heading changes akin to mammalian head-direction cells. Here, we show that self-generated visual motion signals work with E-PG compass neurons so that the direction of exploratory turns can be stored and recalled to maintain the animals heading within an odor plume during flight.

neuroscience↗

bioRxiv2024

Body size and light environment modulate flight speed and saccadic behavior in free flying Drosophila melanogaster

For flying insects, visual control relies on acquiring adequate light, but many circumstances limit this, such as dim environments, high image speeds, or eyes of modest light gathering power. To determine these effects on vinegar flies, we limited light by either placing them in dim conditions, or generating individuals with developmentally smaller eyes, then examined activity levels and three-dimensional flight paths. When simulating dawn and dusk light periods, walking flies increase activity, reflecting their crepuscular nature, and this is stronger for flies with larger eyes. When light switches abruptly, similar to many lab settings, activity associated with crepuscular periods diminishes, as does activity associated with greater facet size. During free flight, we find flight speed decreases similarly in both dim light and small eye conditions, but excess light induces smaller individuals to restore their flight speed. Through a machine learning approach, we confirmed that two features, translational speed and saccade distance, are sufficient to classify treatment groups by light niche, size, and age. Together, these imply that flight changes in smaller individuals result from visual deficits, rather than other elements of body structure.

animal behavior and cognition↗

bioRxiv2023

Evolution of compound eye morphology underlies differences in vision between closely related Drosophila species

Insects have evolved complex visual systems and display an astonishing range of adaptations for diverse ecological niches. Differences in eye size within and between Drosophila species provide the opportunity to study the impact of eye structure on vision. Here we further explored differences in D. mauritiana and its sibling species D. simulans and confirmed that D. mauritiana have rapidly evolved larger eyes as a result of more and wider ommatidia than D. simulans since their recent common ancestor. The functional impact of eye size, and specifically ommatidia size, is often only estimated based on the rigid surface morphology of the compound eye. Therefore, we used 3D synchrotron radiation tomography to measure optical parameters in 3D, predict optical capacity, and compare the modelled vision to in vivo optomotor responses. Our optical models predicted higher contrast sensitivity for D. mauritiana, which we verified by presenting sinusoidal gratings to tethered flies in a flight arena. Similarly, we confirmed the higher spatial acuity predicted for Drosophila simulans with smaller ommatidia and found evidence for higher temporal resolution.

evolutionary biology↗

bioRxiv2021

An inexpensive setup for robust activity tracking in small animals: Portable Locomotion Activity Monitor (pLAM)

O_LIAdvances in computer vision and deep learning have automated animal behaviour studies that previously required tedious manual input. However, tracking activity of small and fast flying animals remains a hurdle, especially in a field setting with variable light conditions. Commercial locomotor activity monitors (LAMs) can be expensive, closed source, and generally limited to laboratory settings. C_LIO_LIHere, we present a portable locomotion activity monitor (pLAM), a mobile activity detector to quantify small animal circadian activity. Our setup uses inexpensive components, is based on open-source motion tracking software, and is easy to assemble and use in the field. It runs off-grid, supports low-light tracking with infrared lights, and can implement arbitrary light cycle colours and brightnesses with programmable LEDs. We provide a user-friendly guide to assembling pLAM hardware and accessing its pre-configured software and guidelines for using it in other systems. C_LIO_LIWe benchmarked pLAM for insects under various lab and field conditions, then compared results to a commercial activity detector. They offer broadly similar activity measures, but our setup captures flight and bouts of motion that are often missed by beam-breaking activity detection. C_LIO_LIpLAM will enable high-throughput quantification of small animal location and activity in a low-cost and accessible manner, crucial to studying behaviour that can help inform conservation and management decisions. C_LI

animal behavior and cognition↗

bioRxiv2020

Measuring Compound Eye Optics with Microscope and MicroCT Images

With a great variety of shapes and sizes, compound eye morphologies give insight into visual ecology, development, and evolution, and inspire novel engineering. In contrast to our own camera-type eyes, compound eyes reveal their resolution, sensitivity, and field of view externally, provided they have spherical curvature and orthogonal ommatidia. Non-spherical compound eyes with skewed ommatidia require measuring internal structures, such as with MicroCT (CT). Thus far, there is no efficient tool to characterize compound eye optics, from either 2D or 3D data, automatically. Here we present two open-source programs: (1) the ommatidia detecting algorithm (ODA), which measures ommatidia count and diameter in 2D images, and (2) a CT pipeline (ODA-3D), which calculates anatomical acuity, sensitivity, and field of view across the eye by applying the ODA to 3D data. We validate these algorithms on images, images of replicas, and CT eye scans from ants, fruit flies, moths, and a bee.

neuroscience↗