Date of Award

5-2014

Document Type

Thesis open access

Abstract

Animal communication allows information to be transferred from a sender to a receiver, and can occur via visual, chemical, auditory, and tactile modalities. Communication behaviors are known to be generally associated with specific brain regions, but it is currently unknown how the cellular morphology of these regions differs in species that quantitatively differ in the use of particular communication modalities. Further, these relationships are rarely considered in an evolutionary context. In this thesis, I investigated the relationship between the use of communication modalities and neural morphologies (in particular, soma size and density) in the brains of six species of lizards: Anolis carolinensis, Aspidoscelis gularis, Hemidactylus turcicus, Leiocephalus carinatus, Sceloporus olivaceus, and Scincella lateralis. I performed behavioral observations of these species, quantifying their rates of visual and chemical communication behaviors. I then collected brains from 10 males of each species and measured soma size and density in two brain regions associated with visual behaviors (the lateral geniculate nucleus, and the optic tectum), one brain region associated with chemical behaviors (the nucleus sphericus), and one brain region generally associated with social behaviors (the preoptic area). I found that species that communicate with higher rates of visual displays had a denser lateral geniculate nucleus, and that species that communicate with a higher percentage of chemical displays had larger somas in the nucleus sphericus. These relationships between communication behaviors and neural morphologies suggest that structures within the brain have evolved convergently in species with similar communication behaviors.

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