Biology subjects

Candelier, R.

Publications and source records attributed to Candelier, R..

6 recordsLinked to original sources

bioRxiv2022

A scalable assay for chemical preference of small freshwater fish

Sensing the chemical world is of primary importance for aquatic organisms, and small freshwater fish are increasingly used in toxicology, ethology, and neuroscience by virtue of their ease of manipulation, tissue imaging amenability, and genetic tractability. However, precise behavioral analyses are generally challenging to perform due to the lack of knowledge of what chemical the fish are exposed to at any given moment. Here we developed a behavioral assay and a specific infrared dye to probe the preference of young zebrafish for virtually any compound. We found that the innate aversion of zebrafish to citric acid is not mediated by modulation of the swim but rather by immediate avoidance reactions when the product is sensed and that the preference of juvenile zebrafish for ATP changes from repulsion to attraction during successive exposures. We propose an information-based behavioral model for which an exploration index emerges as a relevant behavioral descriptor, complementary to the standard preference index. Our setup features a high versatility in protocols and is automatic and scalable, which paves the way for high-throughput preference compound screening at different ages.

animal behavior and cognition↗

bioRxiv2021

Variability and thermal modulation of locomotor statistics in zebrafish

BackgroundVariability is a hallmark of animal behavior. It contributes to survival by endowing individuals and populations with the capacity to adapt to ever-changing environmental conditions. Intra-individual variability is thought to reflect both endogenous and exogenous modulations of the neural dynamics of the central nervous system. However, how variability is internally regulated and modulated by external cues remains elusive. Here we address this question by analyzing the statistics of spontaneous exploration of freely swimming zebrafish larvae, and by probing how these locomotor patterns are impacted when changing the water temperatures within an ethologically relevant range. ResultsWe show that, for this simple animal model, five short-term kinematic parameters - interbout interval, turn amplitude, travelled distance, turn probability and orientational flipping rate - together control the long-term exploratory dynamics. We establish that the bath temperature consistently impacts the means of these parameters, but leave their pairwise covariance unchanged. These results indicate that the temperature merely controls the sampling statistics within a well-defined kinematic space delineated by this robust statistical structure. At a given temperature, individual animals explore the behavioral space over a timescale of tens of minutes, suggestive of a slow internal state modulation that could be externally biased through the bath temperature. By combining these various observations into a minimal stochastic model of navigation, we show that this thermal modulation of locomotor kinematics results in a thermophobic behavior, complementing direct gradient-sensing mechanisms. ConclusionsThis study establishes the existence of a well-defined locomotor space accessible to zebrafish larvae during spontaneous exploration, and quantifies self-generated modulation of locomotor patterns. Intra-individual variability reflects a slow diffusive-like probing of this space by the animal. The bath temperature in turn restricts the sampling statistics to sub-regions, endowing the animal with basic thermophobicity. This study suggests that in Zebrafish, as well as in other ectothermic animals, ambient temperature could be used to efficiently manipulate internal states in a simple and ethological way.

animal behavior and cognition↗

bioRxiv2021

Evolutionary divergence of locomotion in two related vertebrate species

Locomotion exists in diverse forms in nature and is adapted to the environmental constraints of each species1. However, little is known about how closely related species with similar neuronal circuitry can evolve different navigational strategies to explore their environments. We established a powerful approach in comparative neuroethology to investigate evolution of neuronal circuits in vertebrates by comparing divergent swimming pattern of two closely related larval fish species, Danionella translucida (DT) and Danio rerio or zebrafish (ZF)2,3. During swimming, we demonstrate that DT utilizes lower half tail-beat frequency and amplitude to generate a slower and continuous swimming pattern when compared to the burst-and-glide swimming pattern in ZF. We found a high degree of conservation in the brain anatomy between the two species. However, we revealed that the activity of a higher motor region, referred here as the Mesencephalic Locomotion Maintenance Neurons (MLMN) correlates with the duration of swim events and differs strikingly between DT and ZF. Using holographic stimulation, we show that the activation of the MLMN is sufficient to increase the frequency and duration of swim events in ZF. Moreover, we propose two characteristics, availability of dissolved oxygen and timing of swim bladder inflation, which drive the observed differences in the swim pattern. Our findings uncover the neuronal circuit substrate underlying the evolutionary divergence of navigational strategies and how they are adapted to their respective environmental constraints.

neuroscience↗

bioRxiv2019

From behavior to circuit modeling of light-seeking navigation in zebrafish larvae

Bridging brain-scale circuit dynamics and organism-scale behavior is a central challenge in neuroscience. It requires the concurrent development of minimal behavioral and neural circuit models that can quantitatively capture basic sensorimotor operations. Here we focus on light-seeking navigation in zebrafish larvae. Using a virtual reality assay, we first characterize how motor and visual stimulation sequences govern the selection of discrete swim-bout events that subserve the fish navigation in the presence of a distant light source. These mechanisms are combined into a comprehensive Markov-chain model of navigation that quantitatively predict the stationary distribution of the fishs body orientation under any given illumination profile. We then map this behavioral description onto a neuronal model of the ARTR, a small neural circuit involved in the orientation-selection of swim bouts. We demonstrate that this visually-biased decision-making circuit can similarly capture the statistics of both spontaneous and contrast-driven navigation.

animal behavior and cognition↗

bioRxiv2019

A semi-automatic dispenser for solid and liquid food in aquatic facilities

We present a novel, low-footprint and low-cost semi-automatic system for delivering solid and liquid food to zebrafish, and more generally to aquatic animals raised in racks of tanks. It is composed of a portable main module equipped with a contactless reader that adjusts the quantity to deliver for each tank, and either a solid food module or a liquid food module. Solid food comprises virtually any kind of dry powder or grains below two millimeters in diameter, and, for liquid-mediated food, brine shrimps (Artemia salina) and rotifers (Rotifera) have been successfully tested. Real-world testing, feedback and validation have been performed in a zebrafish facility for several months. In comparison with manual feeding this system mitigates the appearance of musculoskeletal disorders among regularly-feeding staff, and let operators observe the animals behavior instead of being focused on quantities to deliver. We also tested the accuracy of both humans and our dispenser and found that the semi-automatic system is much more reliable, with respectively 7-fold and 84-fold drops in standard deviation for solid and liquid food.

biophysics↗

bioRxiv2018

Whole-brain calcium imaging during physiological vestibular stimulation in larval zebrafish

During in vivo functional imaging, animals are head-fixed and thus deprived from vestibular inputs, which severely hampers the design of naturalistic virtual environments. To overcome this limitation, we developed a miniaturized ultra-stable light-sheet microscope that can be dynamically rotated during imaging along with a head-restrained zebrafish larva. We demonstrate that this system enables whole-brain functional imaging at single-cell resolution under controlled vestibular stimulation. We recorded for the first time the dynamic whole-brain response of a vertebrate to physiological vestibular stimulation. This development largely expands the potential of virtual-reality systems to explore complex multisensory-motor integration in 3D.

neuroscience↗