Biology subjects

Couto, A.

Publications and source records attributed to Couto, A..

10 recordsLinked to original sources

bioRxiv2025

Conservation of sensory pathways implies a localised change in the mushroom bodies is associated with cognitive evolution in Heliconius butterflies

Acquisition of novel behaviour is reflected in changes in sensory investment or integration, but the exact nature of these changes is often unclear. Within the Neotropical butterfly tribe, Heliconiini, the genus Heliconius possess 4-fold larger mushroom bodies, an insect learning and memory centre, than closely related Heliconiini. Mushroom body expansion in Heliconius co-occurred with a dietary innovation, and is associated with systematic spatial foraging and extended lifespans. Heliconiini therefore offer an attractive system for studying how behavioural evolution is facilitated by changes in neural systems. Heliconius foraging relies on visual scene memories and, indeed, Heliconius have more stable visual long-term memory, and evidence of visual specialisation in the mushroom bodies. Here, we explore how vision-specific neuroanatomical and behavioural enhancement in Heliconius impacts sensory pathways upstream of the mushroom bodies by assessing investment across the eyes, sensory structures and projection pathways. Despite evidence of refinement in visually-based behaviour, we found no increased investment in visual structures, brain areas or pathways. This suggests that the rapid expansion of the Heliconius mushroom body occurred in a context of conserved detection and processing of visual cues, and that a localised shift within integrative brain centres facilitated the evolution of Heliconius novel behaviours.

evolutionary biology↗

bioRxiv2024

Ancestral complexity and constrained diversification of the ant olfactory system

Ants are a monophyletic but diverse group of social insects whose heightened olfactory ability has been crucial to their evolutionary success. Their complex olfactory system is believed to have evolved due to the expansion of a specialized olfactory subsystem and the associated clade of olfactory receptors. Specifically, ants exhibit specialized antennal hairs known as basiconic sensilla, whose neurons project to a distinctive cluster of numerous, small glomeruli in their antennal lobes. This adaptation is believed to be linked to their social lifestyle, enabling the detection of recognition cues like cuticular hydrocarbons (CHCs), which are essential for nestmate recognition and maintaining colony cohesion. However, our understanding of the ant olfactory system remains incomplete, lacking evolutionary context and phylogenetic breadth, which leaves the complexity in their most recent common ancestor uncertain. We thus conducted a comparative study of neuroanatomical traits across the phylogeny of the Formicidae. Our findings reveal a common blueprint for the ant olfactory pathway, alongside lineage-specific adaptations. This highlights a dynamic evolution, particularly for the CHC-related subsystem. Ancestral trait reconstructions indicate that olfactory sophistication predates the most recent common ancestor of ants. Additionally, we found that the chemical complexity of species-specific recognition cues is associated with neuronal investment within the olfactory system. Lastly, behavioral experiments on anatomically divergent ant species show that, despite variation in neuroanatomical traits, ants consistently discriminate nestmates from non-nestmates. This suggests that the evolution of ants olfactory system integrates sensory adaptations to diverse chemical environments, facilitating communication, a key to social behaviors.

evolutionary biology↗

bioRxiv2024

Inclusion of Salicornia ramosissima biomass in diets for juvenile whiteleg shrimp (Penaeus vannamei) induces favourable but transient effects in the immune and oxidative status

The whiteleg shrimp, Penaeus vannamei, is a highly valued and globally produced crustacean species. However, the rising cost of shrimp feed, exacerbated by increasing cereal prices, prompts the exploration of cost-effective and sustainable formulations for shrimp farming. This study investigates the potential of Salicornia ramosissima, a non-edible biomass co-product, as a substitute for wheat meal in juvenile whiteleg shrimp diets, aiming to create economically and ecologically sound formulations. The present study aimed to assess the impact of incorporating S. ramosissima into whiteleg shrimp aquafeeds on various aspects of shrimp development, including growth performance, survival, immune status, and oxidative status. A commercial-like diet was formulated and served as control, whereas four other diets contained S. ramosissima stems or a combination of leaves and seeds, both at inclusion levels of 5% and 10%, in addition to the control diet. Whiteleg shrimps were fed the experimental diets for 31 and 55 days, followed by a bacterial bath challenge to gauge their immune response to pathogens. At the end of the feeding period, whiteleg shrimps growth performance and survival rates remained consistent across all diets. However, whiteleg shrimp fed diets with S. ramosissima inclusion consumed more feed to achieve similar weights to those fed on the control diet, particularly in diets containing leaves and seeds at a 10% inclusion level, likely due to lower digestibility of dry matter, lipids, and energy. While S. ramosissima biomass inclusion did not affect shrimp weight, relative growth rate, or survival, it did lead to higher feed conversion ratios and feed intake, suggesting differences in nutrient digestibility and metabolic utilization. Additionally, S. ramosissima inclusion affected whiteleg shrimps overall body composition, particularly moisture and ash content. Dietary S. ramosissima inclusion modulated antioxidant enzyme activity in the shrimps hepatopancreas, indicating potential health improvements. The study also observed gene expression changes related to antioxidant enzymes, indicating an overall down-regulation with the inclusion of S. ramosissima. Despite challenges in feeding efficiency, the inclusion of S. ramosissima, especially stems, shows promise in reducing feed costs by utilizing a by-product. Furthermore, S. ramosissima inclusion led to subtle changes in certain plasma humoral parameters and hepatopancreas gene expression. Although some immune parameters varied, these effects appeared to diminish over time. In conclusion, this study highlights the potential of S. ramosissima as a functional feed ingredient capable of enhancing shrimps antioxidant response, aligning with global resource optimization and sustainability initiatives.

immunology↗

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↗

bioRxiv2023

Enhanced long-term memory and increased mushroom body plasticity in Heliconius butterflies

As highly labile structures on both individual and evolutionary time-scales, the mushroom bodies, a key site of learning and memory in insects, are an excellent model for investigating the evolution of cognitive variation. We explored the behavioural consequences of mushroom body expansion in Heliconius butterflies, which possess greatly expanded mushroom bodies relative to their closest outgroups. We conducted long-term visual memory assays across three Heliconius and three other Heliconiini species using trained food-colour associations. We confirm robust differences between clades, with Heliconius exhibiting greater fidelity to the trained colour after 8 days without reinforcement compared to other Heliconiini, with further evidence of stable preferences at 13 days. We extended this analysis to consider the plastic response of the mushroom body calyces over this time period, measuring the volume of the mushroom body calyx, and the number of neurons and synapses it contains. We find substantial post-eclosion expansion and synaptic pruning in calyx of Heliconius erato, but not in Dryas iulia. In Heliconius erato, visual associative learning experience specifically is associated with a greater retention of calyceal synapses. At an individual level, fidelity to the trained colour in Heliconius erato was also positively correlated with synapse number. These results point to an enhanced visual long-term memory across Heliconius, facilitated not only by phylogenetic expansion of the mushroom body, but also changes in its developmental response to learning experience. The co-evolution of mushroom body expansion, plasticity and specific behaviours provides an important case study in the evolution of cognition. Significance StatementHow are cognitive differences between species supported by evolutionary changes in the brain? We investigated this question using Heliconius butterflies which have expanded mushroom bodies, a region of the insect brain involved in learning and memory. We show that Heliconius have more stable visual long-term memories and exhibit more substantial age- and experience-related plasticity than a closely related genus with smaller mushroom bodies. Recall accuracy was also predicted by synapse number in Heliconius erato, but not Dryas iulia, suggesting functional importance. These results suggest that increases in the size of specific brain regions and changes in their plastic response to experience may co-evolve to shape the evolution of cognition.

animal behavior and cognition↗

bioRxiv2022

Rapid expansion and visual specialization of learning and memory centers in Heliconiini butterflies

How do neural systems evolve to support new behaviors? Changes in the abundance and diversity of neural cell types, and their connectivity, shape brain composition and provide the substrate for behavioral variation. We describe a striking example of neural elaboration in an ecologically diverse tribe of Heliconiini butterflies. By building extensive new datasets of neural traits across the tribe, we identify major bursts in the size and cellular composition of the mushroom bodies, central brain structures essential for learning and memory. These expansion events are associated with increased innervation form visual centers and coincide with enhanced performance in multiple cognitive assays. This suite of neural and cognitive changes is likely tied to the emergence of derived foraging behaviors, facilitated by localized specialization of neural networks. One-Sentence SummaryMajor shifts in brain composition and behavior in butterflies with unique foraging and dietary behaviors.

evolutionary biology↗

bioRxiv2022

Efficient generation of lower induced Motor Neurons by coupling Ngn2 expression with developmental cues

Human pluripotent stem cells (hPSCs) are a powerful tool for disease modelling and drug discovery, especially when access to primary tissue is limited, such as in the brain. Current neuronal differentiation approaches use either small molecules for directed differentiation or transcription-factor-mediated programming. In this study we coupled the overexpression of the neuralising transcription factor Neurogenin2 (Ngn2) with small molecule patterning to differentiate hPSCs into lower induced Motor Neurons (liMoNes). We showed that this approach induced activation of the motor neuron (MN) specific transcription factor Hb9/MNX1, using anHb9::GFP-reporter line, with up to 95% of cells becoming Hb9::GFP+. These cells acquired and maintained expression of canonical early and mature MN markers. Molecular and functional profiling revealed that liMoNes resembled bona fide hPSC-derived MN differentiated by conventional small molecule patterning. liMoNes exhibited spontaneous electrical activity, expressed synaptic markers and formed contacts with muscle cells in vitro. Pooled, multiplex single-cell RNA sequencing on 50 cell lines revealed multiple anatomically distinct MN subtypes of cervical and brachial, limb-innervating MNs in reproducible quantities. We conclude that combining small molecule patterning with Ngn2 can facilitate the high-yield, robust and reproducible production of multiple disease-relevant MN subtypes, which is fundamental in the path to propel forward our knowledge of motoneuron biology and its disruption in disease.

neuroscience↗

bioRxiv2021

Single-nucleus sequencing reveals enriched expression of genetic risk factors sensitises Motor Neurons to degeneration in ALS

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disorder characterised by a progressive loss of motor function. The eponymous spinal sclerosis observed at autopsy is the result of the degeneration of extratelencephalic neurons, Betz cells (ETNs, Cortico-Spinal Motor Neuron). It remains unclear why this neuronal subtype is selectively affected. To understand the unique molecular properties that sensitise these cells to ALS, we performed RNA sequencing of 79,169 single nuclei from cortices of patients and controls. In unaffected individuals, we found that expression of ALS risk genes was significantly enriched in THY1+-ETNs and not in other cell types. In patients, these genetic risk factors, as well as genes involved in protein homeostasis and stress responses, were significantly induced in a wide collection of ETNs, but not in neurons with more superficial identities. Examination of oligodendroglial and microglial nuclei revealed patient-specific changes that were at least in part a response to alterations in neurons: downregulation of myelinating genes in oligodendrocytes and upregulation of a reactive state connected to endo-lysosomal pathways in microglia. Our findings suggest that the selective vulnerability of extratelencephalic neurons is partly connected to their intrinsic molecular properties sensitising them to genetics and mechanisms of degeneration. Graphical abstract and working model O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/452054v2_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@11237fdorg.highwire.dtl.DTLVardef@119f3ceorg.highwire.dtl.DTLVardef@d56c69org.highwire.dtl.DTLVardef@1c087e1_HPS_FORMAT_FIGEXP M_FIG Our study highlights cell type specific changes in premotor/motor cortex of sporadic ALS patients. Specifically, we identify upregulation of synaptic molecules in excitatory neurons of upper cortical layers, interestingly correlating to hyperexcitability phenotypes seen in patients. Moreover, excitatory neurons of the deeper layers of the cortex, that project to the spinal cord and are most affected by the disease, show higher levels of cellular stresses than other neuronal types. Correspondently, oligodendrocytes transition from a highly myelinating state to a more neuronally engaged state, probably to counteract stressed phenotypes seen in excitatory neurons. At the same time, microglia show a reactive state with specific upregulation of endo-lysosomal pathways. C_FIG

neuroscience↗

bioRxiv2020

Re-emergence and diversification of a specialised antennal lobe morphology in ithomiine butterflies

How an organisms sensory system functions is central to how it navigates its environment and meets the behavioural challenges associated with survival and reproduction. Comparing sensory systems across species can reveal how facets of behaviour and ecology promote adaptive shifts in the relative importance of certain environmental cues. The insect olfactory system is prominent model for investigating how ecological factors impact sensory reception and processing. Notably work in Lepidoptera led to the discovery of vastly expanded structures, termed a macroglomerular complex (MGC), within the primary olfactory processing centre. These structures typically process pheromonal cues and provide a classic example of how variation in size can influence the functional processing of sensory cues. Though prevalent across moths, the MGC was lost during the early evolution of butterflies, consistent with evidence that courtship initiation in butterflies is primarily reliant upon visual cues, rather than long distance olfactory signals like pheromones. However, a MGC has recently been reported to be present in a species of ithomiine, Godryis zavaleta, suggesting this once lost neural adaptation has re-emerged in this clade. Here, we show that MGCs, or MGC-like morphologies, are indeed widely distributed across the ithomiine tribe, and vary in both structure and the prevalence of sexual dimorphism. Based on patterns of variation across species with different chemical ecologies, we suggest that this structure is involved in the processing of both plant and pheromonal cues, of interlinked chemical constitution, and has evolved in conjunction with the increased importance and diversification of plant derived chemicals cues in ithomiines.

evolutionary biology↗

bioRxiv2018

Heat-stress triggers MAPK crosstalk to turn on the hyper-osmotic response pathway

Cells make decisions based on a combination of external and internal signals. In yeast, the high osmolarity response (HOG) is a mitogen-activated protein kinase (MAPK) pathway that responds to a variety of stimuli, and it is central to the general stress response. Here we studied the effect of heat-stress (HS) on HOG. Using live-cell reporters and genetics, we show that HS promotes Hog1 phosphorylation and gene expression, exclusively via the Sln1 phosphorelay branch, and that the strength of the activation is larger in yeast adapted to high external osmolarity. HS stimulation of HOG is indirect. First, we found that it depends on the operation of a second MAPK pathway, the cell-wall integrity (CWI), a well-known mediator of HS. Second, we show that HS causes glycerol loss via the channel Fps1, and that strictly requires the CWI MAPK Slt2. Third, blocking glycerol efflux also blocks HOG activation, strongly suggesting that it is the resulting loss of turgor by the loss of the accompanying water what causes HOG stimulation. Thus, taken together, our findings highlight a central role for Fps1, and the metabolism of glycerol, in the communication between the yeast MAPK pathways, essential for survival and reproduction in changing environments.

cell biology↗