Year of Publication
Master of Science (MS)
Arts and Sciences
Dr. S. Randal Voss
Ambystoma tigrinum undergoes an obligatory metamorphosis while A. mexicanum fails to metamorphose and exhibits paedomorphosis. While it is clear that salamander paedomorphosis is associated with genetic changes that delay developmental timing, it is not clear when and how these changes manifest during development. It is possible that paedomorphic and metamorphic larvae show equivalent patterns of developmental until late in the larval period, when brain regions become competent to stimulate the release of metamorphic hormones. To test this hypothesis, I compared gene expression patterns between the brains of A. mexicanum and A. t. tigrinum larvae. In support of the developmental equivalence hypothesis, 114 differentially expressed genes (DEGs) were identified in common between the species and all but 2 showed the same temporal pattern of expression. However, more DEGs were identified uniquely from each species. In particular, several genes that are associated with the hypothalamus-pituitaryinterrenal axis, which is implicated in metamorphic regulation in amphibians, exhibited significant expression differences between A. mexicanum and A. t. tigrinum larvae. The results show that metamorphic and paedomorphic modes of development are associated with different transcriptional programs in the brain and these programs diverge during early larval development.
Boley, Meredith A., "A COMPARATIVE STUDY OF LARVAL GENE EXPRESSION BETWEEN A PAEDOMORPHIC AND METAMORPHIC SPECIES OF AMBYSTOMATID SALAMANDER" (2009). University of Kentucky Master's Theses. 585.