Biology subjects

Sayre, M. E.

Publications and source records attributed to Sayre, M. E..

7 recordsLinked to original sources

bioRxiv2026

Deep conservation of head direction circuits in bees, ants and flies

To navigate, animal brains must continuously estimate the bodys heading in space and compare it with internal goals to guide movement. In the fruit fly Drosophila melanogaster a neural circuit in the central complex of the brain serves as an internal compass, exploiting a network architecture called a ring attractor1, 2. While this region is highly conserved and involved in navigation in many insects3, 4, it remains unclear whether the fly circuit represents a general blueprint for head direction computation, or whether different ecologies have driven distinct circuit solutions. Using synaptic-resolution circuit mapping, we identified homologous head direction networks in bees and ants and compared them to the fly circuit. We show that the insect head direction network is conserved across at least 300 million years of evolution. At the level of cell types and projection patterns, all studied species share a nearly identical neural layout, both qualitatively and quantitatively. At the synaptic level, however, the fly and bee circuits differed fundamentally. The distinct wiring principles of homologous neurons expose highly evolvable elements within this otherwise stable circuit. Using these differences in circuit architecture to constrain computational models, we show that both the bee and fly circuits can effectively function as ring attractors with similar, yet distinct, properties. These results demonstrate that complex neural circuits can remain stable over many hundreds of millions of years, while still offering access points for evolution to flexibly adjust neural computations to changing ecological demands, illustrating how evolution balances stability and flexibility in brain circuits.

neuroscience↗

bioRxiv2026

A multi-resolution imaging and analysis pipeline for comparative circuit reconstruction in insects

Connectomics has become essential for the study of brain function, yet for most research groups it remains prohibitively costly in imaging time, data storage, and analysis. Here, we present an imaging, processing, and analysis pipeline for multi-resolution image acquisition and circuit reconstruction. Applied to the central complex of six insect species, we were able to obtain global projectomes at cellular resolution (40-50 nm) with embedded local connectomes describing key computational compartments at synaptic resolution (8-12 nm). We provide standardized protocols for volume EM sample preparation, image acquisition and image alignment, combined with existing methods for {micro}CT block trimming, automatic segmentation, synapse detection, collaborative skeleton tracing with CATMAID, and segmentation proofreading via CAVE. We validated our workflow by reconstructing head direction cells across all six insect species, which revealed deep conservation at the level of cell types, cell numbers and projection patterns, while also revealing circuit level specializations. Overall, our pipeline democratizes comparative connectomics by making this method accessible for small research groups with modest resources.

neuroscience↗

bioRxiv2025

Caste- and Sex-Specific Differential Investment in Brain Regions of Australian Ants

Even within a single species, closely related individuals exhibit distinct lifestyles that demand different information processing requirements. Worker ants are ambulatory and handle tasks like colony maintenance and foraging, while winged reproductive castes focus on mating and colony founding. Here, we compare the volumes of functionally distinct brain regions across alate males, alate females, and workers in two species of ants native to Australia, Myrmecia midas and Rhytidoponera metallica, to assess adaptations to behavioural, ecological, and locomotor demands. Female castes in both species had larger brains with pronounced mushroom bodies, supporting their broader behavioural repertoire and navigational tasks. In comparison, males exhibited smaller brains but enlarged optic lobes and central complexes, highlighting the significance of vision and orientation in mate searching. Species-specific patterns were also noted: R. metallica individuals consistently had larger antennal lobes and smaller optic lobes across castes, indicating a reliance on olfactory cues. However, the mushroom bodies remained comparatively similar. These findings demonstrate how caste- and species-specific sensory demands shape neural architecture and serve as a basis for understanding the interplay between brain structure and function.

zoology↗

bioRxiv2022

Neuroanatomy of stomatopod central complexes offers putative neural substrate for oriented behaviors in crustaceans

All insects studied to date possess a centrally located group of neuropils, known collectively as the central complex, that has been implicated in sensory integration and motor action selection. Among the functions prescribed to the central complex, none is perhaps as intriguing as its role in orientation and navigation. Neurobiological correlates of both current and desired headings have been described in insect CXs. Despite the diversity of arthropods, understanding of the CX as a navigational center originates entirely from terrestrial insects. Stomatopod crustaceans, commonly referred to as mantis shrimps, form an order of predatory marine crustaceans with intricate and diverse visual systems that maintain the distinction of being the only fully aquatic animal known to utilize the navigational strategy of path integration. They utilize idiothetic, celestial, and landmark cues to orient in the benthos. Here, we investigate the neuroanatomy of adult and developing mantis shrimp central complexes and associated neuropils to begin understanding this brain region in a sensorially and behaviorally complex crustacean.

neuroscience↗

bioRxiv2021

A projectome of the bumblebee central complex

Insects have evolved diverse and remarkable strategies for navigating in various ecologies all over the world. Regardless of species, insects share the presence of a group of morphologically conserved neuropils known collectively as the central complex (CX). The CX is a navigational hub, involved in sensory integration and coordinated motor activity. Despite the fact that our understanding of navigational behavior comes predominantly from ants and bees, most of what we know about the underlying neural circuitry of such behavior comes from work in fruit flies. Here we aim to close this gap, by providing the first comprehensive map of all major columnar neurons and their projection patterns in the CX of a bee. We find numerous components of the circuit that appear to be highly conserved between the fly and the bee, but also highlight several key differences which are likely to have important functional ramifications.

neuroscience↗

bioRxiv2020

Evolution of mushroom body inversion and associated gyriform neuropils parallel the evolved transposition of the mammalian hippocampus

Neural organization of mushroom bodies is largely consistent across insects, whereas the ancestral ground pattern diverges broadly across crustacean lineages, resulting in successive loss of columns and the acquisition of domed centers retaining ancestral Hebbian-like networks and aminergic connections. We demonstrate here a major departure from this evolutionary trend in Brachyura, the most recent malacostracan lineage. Instead of occupying the rostral surface of the lateral protocerebrum, mushroom body calyces are buried deep within it, with their columns extending outwards to an expansive system of gyri on the brains surface. The organization amongst mushroom body neurons reaches extreme elaboration throughout its constituent neuropils. The calyces, columns, and especially the gyri show DC0 immunoreactivity, an indicator of extensive circuits involved in learning and memory.

evolutionary biology↗

bioRxiv2019

Mushroom Body Homology and Divergence across Pancrustacea

Descriptions of crustacean brains have mainly focused on three highly derived lineages: the reptantian infraorders represented by spiny lobsters, lobsters, and crayfish. Those descriptions advocate the view that dome- or cap-like neuropils, referred to as "hemiellipsoid bodies," are the ground pattern organization of centers that are comparable to insect mushroom bodies in processing olfactory information. Here we challenge the doctrine that hemiellipsoid bodies are a derived trait of crustaceans, whereas mushroom bodies are a derived trait of hexapods. We demonstrate that mushroom bodies typify lineages that arose before Reptantia and exist in Reptantia. We show that evolved variations of the mushroom body ground pattern are, in some lineages, defined by extreme diminution or loss and, in others, by the incorporation of mushroom body circuits into lobeless centers. Such transformations are ascribed to modifications of the columnar organization of mushroom body lobes that, as shown in Drosophila and other hexapods, contain networks essential for learning and memory. We propose that lobed mushroom bodies distinguish crustaceans that negotiate the multidimensionality of complex ecologies, where continuous updating of multistimulus valence and memory is paramount.

neuroscience↗