Effects of Habitat and Social Complexity on Brain Size, Brain Asymmetry and Dentate Gyrus Morphology in Two Octodontid Rodents

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

BRAIN BEHAVIOR AND EVOLUTION

KARGER

Lugar: Basel; Año: 2016

0006-8977

Navigational and social challenges due to habitat conditionsand sociality are known to influence dentate gyrus (DG) morphology,yet the relative importance of these factors remainsunclear. Thus, we studied three natural populations of O. lunatus(Los Molles) and Octodon degus (El Salitre and Rinconada),two caviomorph species that differ in the extent ofsociality and with contrasting vegetation cover of habitatused. The brains and DG of male and female breeding deguswith simultaneous information on their physical and socialenvironments were examined. The extent of sociality wasquantified from total group size and range area overlap. O.degus at El Salitre was more social than at Rinconada andthan O. lunatus from Los Molles. The use of transects to quantifycover of vegetation (and other physical objects in thehabitat) and measures of the spatial behavior of animals indicatedanimal navigation based on unique cues or globallandmarks is more cognitively challenging to O. lunatus.During lactation, female O. lunatus had larger brains than males.Relative DG volume was similar across sexes and populations.The right hemisphere of male and female O. lunatushad more cells than the left hemisphere, with DG directionalasymmetry not found in O. degus . Degu population differencesin brain size and DG cell number seemed more responsiveto differences in habitat than to differences in sociality.Yet, large-sized O. degus (but not O. lunatus ) that ranged overlarger areas and were members of larger social groups hadmore DG cells per hemisphere. Thus, within-population variationin DG cell number by hemisphere was consistent witha joint influence of habitat and sociality in O. degus at ElSalitre.