Current Research in Evo-Devo

My masters work can be sub-divided into three sections with the prominent research theme being Evo-Devo/modularity.

1) EMBRYOGENESIS, AND REGULATROY GENE EXPRESSION; PAX6 AND SONIC HEDGE HOG

2) HORMONE INDUCED OVULATION

3) COMPARATIVE OCULAR HISTOLOGY OF THREE ENDEMIC PAEDOMORPHIC SALAMANDER SPECIES (EURYCEA NANA, E. SOSORUM, AND E. RATHBUNI) Evolutionary Developmental Biology 

Esosorum late5-1

Eurycea sosorum embryo (late stage, note the amount of pigmentation in the eye and throughout the head)

I am broadly interested in the study of herpetology, my question of interest resides largely in the fairly new integrative discipline of evolutionary developmental biology. I am interested in the evolution of genes conserved across taxa and the molecular mechanisms underlying deviations observed during embryogenesis, ultimately leading to the variation seen among organisms. I am specifically interested in the genes (e.g. Pax6 and shh) that regulate ocular development between two morphologically different salamander sister species (Eurycea nana and Eurycea rathbuni). While extensive work has been accomplished with a cavefish species (Astyanax mexicanus), salamanders, the only other aquatic cave vertebrate and the only stygobitic tetrapod, have yet to be explored. Phylogenetic analyses indicate close relationships between the 13 recognized species of south central Texas Eurycea, and several invasions of karst habitat. E rathbuni embryo2Thus, the south central Texas Eurycea clade is composed of species with structural variations resulting in a unique continuum of karst morphologies. The variation exhibited by the clade suggests differential gene expression and regulation, rather than different genes, is responsible for the development of drastically different morphologies, particularly since some of the variation occurs within single species. Therefore, these salamanders present an ideal system in which to address the question “What are the underlying differences in regulation of developmental genes responsible for differing morphologies?” I plan to gather data using the Texas State University Department of Biology microscopy facility to uncover the respective gene expression at different embryo stages.

Eurycea sosorum showing the developing brain and eyes. Pax6 (red), Shh (green), and Hoechst a nuclear stain (blue)

Eurycea sosorum showing the developing brain and eyes. Pax6 (red), Shh (green), and Hoechst a nuclear stain (blue).

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Eurycea rathbuni, showing the development of a lens placode. Pax6(red) and Hoechst (blue).

Given Pax6’s involvement in ocular development, in the future I plan to extend the investigation to encompass species representing intermediate phenotypes of the south central Texas Eurycea salamander continuum and sequence divergence between and among species. My key objectives are to explore the molecular and developmental mechanisms underlying the evolution of phenotypes to karst environments by comparing the Texas blind salamander (E.rathbuni) and San Marcos salamander (E. nana), a study never before addressed in a cave-dwelling salamander species nor within such a morphologically unique clade.