Brain morphology and encephalization quotient in sigmodontine rodents (Rodentia: Cricetidae): a comparative study based on 3D reconstructions

Abstract

Sigmodontine rodents (Cricetidae, Sigmodontinae) represent one of the most diverse groups of cricetids, exhibiting remarkable ecological and morphological variation. However, their neuroanatomical study has been limited. This paper presents a preliminary exploration of the variation in encephalization quotient (EC) and brain morphology in 21 species belonging to 9 tribes, considering their different locomotor habits (i.e., terrestrial, arboreal, semi-aquatic, fossorial, and wading). The results obtained show that semi-aquatic and arboreal species have relatively higher EC values, perhaps associated with a greater sensory and be-havioral demand in complex three-dimensional environments. In contrast, fossorial species exhibit lower EC values, an aspect that could be linked to less behavioral complexity and a greater investment in muscle mass. Judged in general, the brain morphology of the sigmo-dontines is conservative, with the most evident variations being in the relative size of the olfactory bulbs.