Inside the head of Crotalus durissus LINNAEUS, 1758 (Serpentes, Viperidae, Crotalinae): Macroscopic description of the brain with ontogenetic insights.

Neuroanatomy studies in vertebrates have garnered significant attention in recent years, particularly driven by advancements in computerized tomography imaging techniques. Nonetheless, these advancements remain largely constrained to specific vertebrate groups, notably mammals, birds, and fish, leaving studies in reptiles at an incipient stage. In this work, we aim to describe in detail the macroscopic morphology of the brain of Crotalus durissus based on a sample of four young and four adult individuals-three male and five female specimens, providing the first detailed description of the brain with a relatively modest sample available for reptiles. Our results show that the major macroscopic features identified in C. durissus suggest a brain structure typical of a multi-habitat and cathemeral/nocturnal alethinophidian species, thereby contributing significant data to the understanding of brain morphological evolution in snakes. Brain measurements showed distinct scaling patterns related to snout-vent length and head length, with variables such as brain length and cerebral hemisphere length decreasing with SVL, while others like olfactory bulb length and medulla oblongata width increased. Additional differences were observed comparing juveniles and adults, with adults generally exhibiting larger mean values for cerebellum and medulla oblongata measurements. However, the small sample size highlights the need for future studies with larger datasets to validate these findings and explore the developmental trajectories in greater detail.