Biology subjects

Gourgou, E.

Publications and source records attributed to Gourgou, E..

5 recordsLinked to original sources

bioRxiv2026

A dynamical circuit model for C. elegans chemotaxis with emergent sharp turns

With its rigorously characterized connectome, the nematode Caenorhabditis elegans is a powerful model organism to study the fundamental roles of neuronal circuits in behavior. However, despite the breadth of research, many questions remain unanswered regarding how these organisms are able to successfully navigate their environment. Here, we present a biologically grounded dynamical circuit model for the investigation of sensory-guided behavior during C. elegans chemotaxis. Our model consists of the chemosensory neuron AWA, interneurons RIM and RIA, motor neurons, including SMDs and RMDs, and body wall muscles that provide proprioceptive feedback through stretch receptors. The connectivity prioritizes functional and dynamical correspondence with the biological circuit over one-to-one anatomical fidelity. After optimization with an evolutionary algorithm, the model locomotes toward a chemical attractant, effectively capturing nematode chemotactic behavior. A key emergent property of the model that contributes to successful chemotaxis is the ability to make sharp turns, which resemble the omega turns of living nematodes. The direction and magnitude of these turns depend on the phase of the ongoing locomotory cycle. The sharp turning behavior is triggered by decreases in the concentration of the attractant. In the model, decreases in attractant concentration levels reduce AWA activity, which in turn triggers disinhibition of RIM activity and subsequent changes in RIA oscillatory activity. The ensuing coordinated changes in downstream motor neurons' activity patterns produce sharp turns, which correct the model worm's path to head toward the attractant source and, after reaching the concentration gradient peak, allow the model worm to remain in its proximity. The proposed framework and its emergent dynamics provide new insights into how circuit-level dynamics may generate key features of C. elegans chemotactic behavior, including omega-like turns. In parallel, it generates experimentally testable hypotheses about how the participating neuronal elements contribute to chemotactic behavior.

neuroscience↗

bioRxiv2026

Behavioural plasticity in Caenorhabditis elegans navigating dynamic granular environments

The mechanisms that steer behavioural plasticity in complex environments remain poorly understood. Here, we introduce Peb2les, a quasi-two-dimensional granular arena, for the behavioural assessment of Caenorhabditis elegans nematodes, as they interact with deformable, dynamic terrains. Using customized deep-learning-based methods, we track both nematodes and particles to characterize coupled animal-environment dynamics. We find that nematodes locomotor performance depends on particle density and surface properties, and is largely independent of mechanosensation, whereas functional touch sense is required for the initial decision to enter rough-textured arenas. In addition, we identify a previously undescribed touch-seeking behaviour that partially depends on mechanosensation, in which C. elegans actively return to the granular arena after exiting. In parallel, locomoting nematodes rearrange and stack surrounding particles, continuously modifying the granular terrain. Together, these findings establish Peb2les as a versatile platform for probing the mechanism and limits of behavioural plasticity and locomotory adaptability of nematodes in sensory-enriched, soil-like environments, while also providing insight into the potential evolutionary origins of adaptive touch-seeking behaviours in animals.

animal behavior and cognition↗

bioRxiv2021

3-dimensional arenas for the assessment of C. elegans behavior

C. elegans nematodes are a well-established model organism in numerous fields of experimental biology. In nature, C. elegans live in a rich 3-dimensional environment. However, their behavior has been assessed almost exclusively on the open, flat surface of NGM (Nematode Growth Medium) plates, the golden standard for C. elegans culture in the lab. We present two methods to build 3-dimensional behavioral arenas for C. elegans, by casting, and by directly 3D printing NGM hydrogel. The latter is achieved by using a highly customized fused deposition modeling (FDM) 3D-printer, modified to employ NGM hydrogel as ink. The result is the advancement of 3-dimensional complexity of behavioral assays. To demonstrate the potential of our method, we use the 3D-printed arenas to assess C. elegans physical barriers crossing. C. elegans decision to cross physical obstacles is affected by aging, physiological status (i.e., starvation), and prior experience. The 3D-printed structures can be used to spatially confine C. elegans behaviors, i.e., egg laying. We consider these findings a decisive step toward characterizing C. elegans 3-dimensional behavior, an area long overlooked due to technical constrains. We envision our method of 3D-printing NGM arenas as a powerful tool in behavioral neurogenetics, neuroethology, and invertebrate model organisms neurobiology.

bioengineering↗

bioRxiv2018

Caenorhabditis elegans locomotion dynamics is affected by internally localized magnetic fields

C. elegans nematodes are a model organism used broadly to investigate the impact of environmental factors on physiology and behavior. Here, C. elegans with internalized paramagnetic nanoparticles were placed inside magnetic field to explore effects on locomotion. We hypothesize that internalized paramagnetic nanoparticles combined with external magnetic field affect C. elegans locomotion machinery. To test our hypothesis, we used young adult C. elegans fed on bacteria mixed with paramagnetic nanoparticles of 1 m, 100 nm and 40 nm diameter. The presence of nanoparticles inside the worms body (alimentary canal, body muscle) was verified by fluorescent and electron microscopy. A custom-made software was used to track freely moving C. elegans in the absence or presence of magnetic field sequentially for 200+200 sec. We used established metrics to quantify locomotion-related parameters, including posture, motion and path features. Key features of C. elegans locomotion (increased body bends and stay ratio, decreased range, forward movement, and speed along the magnetic field) were affected in worms with internalized nanoparticles of 100 nm and 1 m in the presence of magnetic field, in contrast to untreated worms. Our work contributes on clarifying the effect of internalized paramagnetic nanoparticles, combined with magnetic field, on C. elegans locomotion. Summary StatementC. elegans with internalized paramagnetic nanoparticles are placed inside magnetic field to explore effects on locomotion. Results support the potential of C. elegans to investigate the impact of the above environmental factors on behavior.

biophysics↗

bioRxiv2017

A mathematical and computational model of the calcium dynamics in Caenorhabditis elegans ASH sensory neuron

We propose a mathematical and computational model that captures the stimulus-generated Ca2+ transients in the C. elegans ASH sensory neuron. The model is built based on biophysical events and molecular cascades known to unfold as part of neurons Ca2+ homeostasis mechanism, as well as on Ca2+ signaling events. The state of ion channels is described by their probability of being activated or inactivated, and the remaining molecular states are based on biochemically defined kinetic equations with phenomenological adjustments. We estimate the parameters of the model using experimental data of hyperosmotic stimulus-evoked Ca2+ transients detected with a FRET sensor in young and aged worms, unstressed and exposed to oxidative stress. We use a hybrid optimization method composed of a multi-objective genetic algorithm and nonlinear least-squares to estimate the model parameters. We first obtain the model parameters for young unstressed worms. Next, we use these values of the parameters as a starting point to identify the model parameters for stressed and aged worms. We show that the model, in combination with experimental data, corroborates literature results. In addition, we demonstrate that our model can be used to predict ASH response to complex combinations of stimulation pulses. The proposed model includes for the first time the ASH Ca2+ dynamics observed during both \"on\" and \"off\" responses. This mathematical and computational effort is the first to propose a dynamic model of the Ca2+ transients mechanism in C. elegans neurons, based on biochemical pathways of the cells Ca2+ homeostasis machinery.\n\nSignificance StatementC. elegans is widely used as a model system for monitoring neuronal Ca2+ transients. The ASH neuron is the subject of several such studies, primarily due to its key importance as a polymodal nociceptor. However, despite its pivotal role in C. elegans biology, and the special characteristics of its stimulus-evoked Ca2+ transients (e.g., the \"off\" response), no mathematical or computational model has been developed to include special features of ASH Ca2+ dynamics, i.e. the \"off\" response. The model includes for the first time the ASH Ca2+ dynamics observed during both \"on\" and \"off\" responses, and is the first to propose a dynamical model of the C. elegans Ca2+ transients mechanism based on biochemical pathways of the cells Ca2+ homeostasis machinery.\n\nAbbreviations

neuroscience↗