ESRS 2026 Short-Term Research Grant Report by Gabriel Spanghero

Introduction and objectives
The evolution of sleep remains a critical question in comparative biology, particularly regarding the divergence in slow-wave sleep (SWS) and REM sleep traits in vertebrates. This research stays focused on characterising the neurophysiological and behavioural markers of sleep in snakes, a taxonomic group largely underrepresented in sleep research. The primary objective was to distinguish between states of active wakefulness, quiet wakefulness, and sleep-like states by recording brain oscillations using Morelia spilota and Boa imperator as focal species. Moreover, we aimed to characterise signatures of the electrophysiological sleep in snakes and potentially determine behavioural correlations. By comparing these findings with existing data from other reptiles and mammals, the project aims to provide insights into the ancestral origins of sleep states.

Methodology and institutional collaboration
The experimental phase was conducted at the Centre de Recherche en Neurosciences de Lyon (CRNL) in collaboration with the ACSED animal facility of the Université de Lyon. Lyon was selected as the host site due to its specialised technical infrastructure for sleep research and the expertise of Dr. Christelle Peyron’s team in neurobiology and surgical procedures. Before surgery, high-resolution volumetric imaging (CT-scan and MRI) was performed in a specialised laboratory in Lyon to create 3D skull models and determine precise electrode coordinates for each of the 5 individuals. Neuro-electrophysiological data were captured using advanced wireless bio-loggers (Figure 1). These included bio-loggers for cerebral signals, muscular activity, heart rate, and body acceleration through a tri-axial accelerometer and gyroscope. During experimental trials, we also set up continuous video recording using a wide-angle camera. Because terrarium was constructed with an infra-red lighting roof, and the camera had an infra-red filtering, we were able to record the animal behaviour during 24-h cycle continuously (Figure 2). The study involved baseline recordings at 25ºC, followed by neurophysiological assessments under varying conditions, including post-prandial states and thermal variations (ranging from ≤ 20ºC to ≥ 30ºC). Additionally, specialised treatments such as 6-hour sleep deprivation and constant darkness were implemented to assess homeostatic and circadian influences.

Preliminary findings and technical observations
Throughout my stay in Lyon, we encountered significant technical and biological hurdles, including individual variability in anesthesia susceptibility and unpredictable consequences from surgery outcome. The variability in anaesthesia resulted in the changing of sample size from the proposed five to the final of two Morelia spilota and one Boa imperator specimens, which were successfully obtained. The use of 3D-printed custom casings successfully protected the bio-loggers from physical and chemical damage during the recording sessions (Figure 3). All the data were safely stored in different databases to protect them from causalities that could cause data loss. Currently, the data are being processed and analysed.

Best Regards,

Gabriel Spanghero
PhD student at Universidade Estadual de Campinas
São Paulo, Brazil