Divergent patterns of ocular development and gene expression in the evolution of a subterranean salamander
- Published
- Accepted
- Subject Areas
- Developmental Biology, Evolutionary Studies
- Keywords
- Ocular development, divergent evolution, evolution and development, subterranean salamander
- Copyright
- © 2018 Tovar et al.
- Licence
- This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, reproduction and adaptation in any medium and for any purpose provided that it is properly attributed. For attribution, the original author(s), title, publication source (PeerJ Preprints) and either DOI or URL of the article must be cited.
- Cite this article
- 2018. Divergent patterns of ocular development and gene expression in the evolution of a subterranean salamander. PeerJ Preprints 6:e27301v1 https://doi.org/10.7287/peerj.preprints.27301v1
Abstract
Relatively few studies have focused on the evolution and development of divergent nervous systems. The salamander clade (Eurycea) from the karst regions of central Texas provide an ideal platform for comparing divergent nervous and sensory systems, since some species exhibit extreme phenotypes thought to be associated with inhabiting a subterranean environment, including highly reduced eyes. We describe ocular development and examine early ocular protein expression (Pax6 and Shh), comparing between two salamander species representing two phenotypes: the surface dwelling Barton Springs salamander (E. sosorum) and the obligate subterranean Texas blind salamander (E. rathbuni). Between the two species, similarities during the development of ocular tissue (e.g. optic cup and lens vesicle) were observed during embryogenesis. However, during late stage embryogenesis the two species display markedly different patterns of Pax6 localization, which parallel patterns previously reported in a cavefish. A lens vesicle was observed in E. rathbuniembryos at stage 40, yet the lens is absent in adults, suggesting the regression of the lens during ontogeny. We also include adult histology of the surface dwelling San Marcos salamander (E. nana) and note similarities to E. sosorum. Adult E. rathbunilack major histological features associated with vision; however, eye morphology did not differ significantly between E. rathbuniand E. sosorumin early developmental stages, suggesting a combination of underdevelopment and degeneration contribute to the reduced eyes of adult E. rathbuni.
Author Comment
This is a submission to PeerJ for review.
Supplemental Information
E. rathbuni Pax6 and Shh expression at stage 37 and 40
Dorsal view of eye development in E. rathbuni. Pax6 and Shh expression at stage 37 (A&B), and 40 (C&D).
E. rathbuni Pax6 and Shh expression at stage 37 and 40
Dorsal view of eye development in E. sosorum. Pax6 and Shh expression at stage 37 (A&B), and 40 (C&D).
Eye measurements
Each data point represents the average of the right and left eye standardized by head length for each species and respective stage, early development and adult.