Conflicts of interest: None.
Reduced effects of thyroid hormone on gene expression and metamorphosis in a paedomorphic plethodontid salamander
Article first published online: 1 JUN 2014
© 2014 Wiley Periodicals, Inc.
Journal of Experimental Zoology Part B: Molecular and Developmental Evolution
Volume 322, Issue 5, pages 294–303, July 2014
How to Cite
2014. Reduced effects of thyroid hormone on gene expression and metamorphosis in a paedomorphic plethodontid salamander. J. Exp. Zool. (Mol. Dev. Evol.) 322B:294–303., , , , .
- Issue published online: 9 JUN 2014
- Article first published online: 1 JUN 2014
- Manuscript Accepted: 8 MAY 2014
- Manuscript Received: 3 MAR 2014
- University of Tulsa
- National Science Foundation. Grant Number: DEB 1050322
It has been over a century since Gudernatsch (1912, Wilhelm Roux Arch Entwickl Mech Org 35:457–483) demonstrated that mammalian thyroid gland extracts can stimulate tadpole metamorphosis. Despite the tremendous developmental diversity of amphibians, mechanisms of metamorphosis have mostly been studied in a few model systems. This limits our understanding of the processes that influence the evolution of developmental aberrations. Here we isolated thyroid hormone receptors alpha (TRα) and beta (TRβ) from Oklahoma salamanders (Eurycea tynerensis), which exhibit permanently aquatic (paedomorphic) or biphasic (metamorphic) developmental modes in different populations. We found that TRα and TRβ were upregulated by thyroid hormone (T3) in tail tissues of larvae from metamorphic populations, but basal levels of TR expression and T3 responsiveness were reduced in larvae from paedomorphic populations. Likewise, we found that T3 treatment resulted in complete loss of larval epibranchials in larvae from metamorphic populations, but little to no epibranchial remodeling occurred in larvae from paedomorphic populations over the same duration. This is the first study to directly demonstrate reduced gene expression and metamorphic responses to T3 in a paedomorphic plethodontid compared to metamorphic conspecifics, and the first salamander system to show differential expression of thyroid hormone receptors associated with alternative developmental patterns. J. Exp. Zool. (Mol. Dev. Evol.) 322B: 294–303, 2014. © 2014 Wiley Periodicals, Inc.