Effects of social and ecological complexity on the brain of octodontid rodents

RAUL SOBRERO; ALVARO LY PRIETO; PEDRO FERNANDEZ ABURTO; JORGE MPODOZIS; LUIS EBENSPERGER

Congreso; 1er Congreso Argentino de Biología del Comportamiento; 2013

Our research is aimed to determine the extent to which ecological and social environments have influenced brain evolution. In particular, this work focuses on the effects of physical and social group complexity on hippocampal cytoarchitecture in two species of Chilean endemic rodents. Thus, we studied three natural populations of Octodon degus and O. lunatus, two species that differ in the extent of sociality, and with contrasting conditions of physical complexity. We quantified physical complexity in terms of plant cover, relevant for navigation. The extent of social complexity was inferred from nesting associations and home range overlap through telemetry. Upon quantifying these field measures, a number of male and female radio-collared subjects were recaptured, and euthanized. The brains were fixed, cryoprotected, serially sectioned, mounted and nissl stained. A stereological workstation was used to determine the volume and cell number at the dentate gyrus (DG). Current results indicate increased DG cell number with greater sociality in these Octodontid rodents. Additionally large home range are not apparent association with an increased number of neurons. Also these data revealed asymmetries between brain hemispheres. Octodon brain size scales with body mass, O. lunatus is the brainy rodent. Plant cover is higher in habitats used by O. lunatus.