Biology subjects

Loupasaki, T.

Publications and source records attributed to Loupasaki, T..

3 recordsLinked to original sources

bioRxiv2025

Distinct evolutionary trajectories of two integration centres, the central complex and mushroom bodies, across Heliconiini butterflies

Neural circuits have evolved to produce cognitive processes that facilitate a species variable behavioural repertoire. Underlying this variation are evolutionary forces, such as selection, that operate on changes to circuitry against a background of constraints. The interplay between selection and potentially limiting constraints determine how circuits evolve. Understanding how this process operates requires an evolutionary framework that facilitates comparative analysis of neural traits, within a clear behavioural and functional context. We leverage a large radiation of Heliconiini butterflies to examine how selection shapes the evolution of the central complex and the mushroom bodies, two integration centres in the insect brain involved in spatial navigation. Within the Heliconiini, one genus, Heliconius, performs systematic spatial foraging and navigation to exploit specific plants as a source of pollen, a novel dietary resource. Closely related genera within Heliconiini lack this dietary adaptation, and are more vagrant foragers. The evolution of increased spatial fidelity in Heliconius has led to changes in brain morphology, and in specific learning and memory profiles, over a relatively short evolutionary time scale. Here, using a dataset of 41 species, we show that in contrast to a massive expansion of the mushroom bodies, the central complex and associated visual processing areas are strongly conserved in size and general architecture. We corroborate this by characterising patterns of fine anatomical conservation, including conserved patterns in dopamine and serotonin expression. However, we also identify a divergence in the expression of a neuropeptide, Allatostatin A, in the noduli, and in the numbers of GABA-ergic ellipsoid body ring neurons and their branching in the fan-shaped body, which are essential members of the anterior compass pathway. These differences match expectations of where evolutionary adaptability might occur inside the central complex network and provide rare examples of divergence of these circuits in a shallow phylogenetic context. We conclude that due to the contrasting volumetric conservation of the central complex and the massive volumetric differences in the mushroom bodies, their circuit logics must determine distinct responses to selection associated with divergent foraging behaviours.

neuroscience↗

bioRxiv2024

Mutualisms within light microhabitats drive sensory convergence in a mimetic butterfly community

Niche partitioning within variable habitats can expose species to distinct sensory information. Vision is the primary sensory modality used by many animals to interact with their habitat. However, within diurnal terrestrial ecosystems, little is known if, and how, variation in light environments impact species assemblages and visual system evolution. By studying a diverse, sympatric community of mimetic butterflies, we demonstrate that forest architecture creates a mosaic of light microhabitats that drive adaptive sensory convergence and divergence in both peripheral and central sensory systems. Our study provides insights into the dynamic response of visual systems when confronted with similar ecological challenges, and illustrates the wide-reaching consequences of interspecific mutualisms, such as mimicry, on organismal evolution.

evolutionary biology↗

bioRxiv2024

Mosaic evolution of a learning and memory circuit in Heliconiini butterflies

A critical function of central neural circuits is to integrate sensory and internal information to cause a behavioural output. Evolution modifies such circuits to generate adaptive change in sensory detection and behaviour, but it remains unclear how selection does so in the context of existing functional and developmental constraints. Here, we explore this question by analysing the evolutionary dynamics of insect mushroom body circuits. Mushroom bodies are constructed from a conserved wiring logic, mainly consisting of Kenyon cells, dopaminergic neurons and mushroom body output neurons. Kenyon cells carry sensory identity signals, which are modified in strength by dopaminergic neurons and carried forward into other brain areas by mushroom body output neurons. Despite the conserved makeup of this circuit, there is huge diversity in mushroom body size and shape across insects. However, an empirical framework of how evolution modifies the function and architecture of this circuit is largely lacking. To address this, we leverage the recent radiation of a Neotropical tribe of butterflies, the Heliconiini (Nymphalidae), which show extensive variation in mushroom body size over comparatively short phylogenetic timescales, linked to specific changes in foraging ecology, life history and cognition. To understand the mechanism by which such an extensive increase in size is accommodated through changes in lobe circuit architecture, we first combined immunostainings of structural markers, neurotransmitters and neural injections to generate, to our knowledge, the most detailed description of a Papilionoidea butterfly mushroom body lobe. We then provide a comparative, quantitative dataset which shows that some Kenyon cell populations expanded with a higher rate than others in Heliconius, providing an anatomical parallel to specific shifts in behaviour. Finally, we identified an increase in GABA-ergic feedback neurons essential for non-elemental learning and sparse coding, but conservation in dopaminergic neuron number. Taken together, our results demonstrate mosaic evolution of functionally related neural systems and cell types and identify that evolutionary malleability in an architecturally conserved parallel circuit guides adaptation in cognitive ability.

evolutionary biology↗