Galizia, C. G. | bioRxiv Science

bioRxiv2026

From eye anatomy to navigation: a biologically accurate model of bees polarisation vision

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.

neuroscience↗

bioRxiv2024

Collective flow of circadian clock information in honeybee colonies

Honeybee colonies exhibit a collective circadian rhythm reflecting the periodic dynamics of the environment. Thousands of workers, including those engaged in in-hive tasks, must synchronize in various processes that may be rhythmic, such as nectar inflows, or non-rhythmic, such as brood care but it remains unknown how those different rhythms are integrated into a colony-level circadian rhythm. Using an AI-driven automated tracking system, we obtained uninterrupted long-term tracking of all individuals in two honeybee colonies. We demonstrate that circadian rhythmicity is present across all age groups and that this rhythm is entrained into all individuals, however, with peak activity shifting by up to 2 hours in workers furthest from the entrance. Extensive data analysis and an agent-based model suggest that mechanical interactions between individuals facilitate the transfer of movement speed, and hence Zeitgeber information. Finally, we show that this speed transfer leads to a collective slow wave of activity that initiates at the nest entrance, spreading throughout the nest. This simple mechanism, workers bumping into each other, enables colonies to entrain their rhythm to the daily cycle of the external environment and, because of the spatial organization of the nest, activates different groups of workers sequentially. The speed transfer interactions demonstrate a tightly-tuned mechanism that underlines the elegant self-organization of the superorganism.

animal behavior and cognition↗

bioRxiv2023

Ephaptic coupling between olfactory receptor neurons is sensitive to relative stimulus timing: Implications for odour source discrimination

Insect olfactory receptor neurons (ORNs) are often co-localized within sensilla and exhibit non-synaptic reciprocal inhibition through ephaptic coupling. It has been postulated that this inhibition aids odour source discrimination, as synchronous arrival of different odour molecules (odorants) from a single source should increase ephaptic inhibition, whereas asynchronous arrival of odorants from different sources should decrease ephaptic inhibition. However, it was as yet unknown whether temporal arrival patterns of different odorants indeed modulate ephaptic inhibition, since past studies have focused on ephaptic inhibition of sustained ORN responses to prolonged and constant odour stimuli. However, most natural odour stimuli are not constant but rather transient and fluctuate as a result of dispersion in turbulent plumes in the air. To investigate the role of ephaptic inhibition in olfaction within turbulent environments, we recorded co-localized ORNs in the fruit fly Drosophila melanogaster exposed to dynamic odorant mixtures. We found that ephaptic inhibition does modulate transient ORN responses, and the strength of ephaptic inhibition decreases as the synchrony between arriving odorants decreases. These results support the hypothesis that ephaptic inhibition aids odour source discrimination.

neuroscience↗