The effects of habitat complexity and social behaviour on some brain structures in South American, Octodontid rodents

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

Encuentro; 2012 Association for the Study of Animal Behaviour Winter Meeting: Cognition in the Wild; 2012

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 complexity on brain 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 habitat complexity. We quantified habitat complexity in terms of plant cover and other habitat features likely to act as obstacles or landmarks during movement in these animals. The extent of sociality was inferred from nesting associations through telemetry. Upon completing these field measures, a percentage of male and female subjects were recaptured, and transported to the laboratory where they were euthanized. Then, brains were fixed, cryoprotected, serially sectioned, mounted and stained. During neuroanatomy quantitative analysis we used a stereological workstation to determine volume and cell number at the dentate gyrus. Preliminary results indicate that rodents from more open habitats, with little or low plant cover and greater sociality exhibit fewer hippocampal cells compared to subjects from habitats with relatively high plant cover and reduced sociality.