July 2018
Volume 59, Issue 9
Open Access
ARVO Annual Meeting Abstract  |   July 2018
The lizard third eye
Author Affiliations & Notes
  • Katie Irwin
    Cellular Biology, University of Georgia, Athens, Georgia, United States
  • Ashley Margret Rasys
    Cellular Biology, University of Georgia, Athens, Georgia, United States
    College of Veterinary Medicine, University of Georgia, Athens, Georgia, United States
  • Tathiana Roldan
    Biology, University of Puerto Rico, Cayey, Puerto Rico
  • Douglas B Menke
    Genetics, University of Georgia, Athens, Georgia, United States
  • James D Lauderdale
    Cellular Biology, University of Georgia, Athens, Georgia, United States
    Neuroscience Division of Biomedical and Health Sciences Institute, University of Georgia, Athens, Georgia, United States
  • Footnotes
    Commercial Relationships   Katie Irwin, None; Ashley Rasys, None; Tathiana Roldan, None; Douglas Menke, None; James Lauderdale, None
  • Footnotes
    Support  NSF Grant #1149453
Investigative Ophthalmology & Visual Science July 2018, Vol.59, 577. doi:
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    • Get Citation

      Katie Irwin, Ashley Margret Rasys, Tathiana Roldan, Douglas B Menke, James D Lauderdale; The lizard third eye. Invest. Ophthalmol. Vis. Sci. 2018;59(9):577.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

Purpose : The third eye, commonly known as the parietal eye, is a non-visual, photosensitive parapineal organ found in most lizards, frogs, the tuatara, and some species of fish. The parietal eye of the lizard is remarkably well developed, possessing a lens, cornea, and retina, but little else is currently known about this organ. This project aims to compare the parietal to the lateral eye in the Anolis sagrei lizard, hypothesizing that parietal and lateral eye development employ similar gene networks. Because of the parietal eye’s fascinating eyelike structures, understanding its development in comparison to the lateral eye will provide a unique system, not present in humans or many other vertebrates, for gaining insight into mechanisms underlying formation of vertebrate eye structures.

Methods : A. sagrei eggs were collected from adult lizards, and embryos were removed from their shells and assigned a developmental stage based on morphological criteria. Tissue was then dissected, fixed, and processed for paraffin wax sectioning. After sectioning, tissue was stained with hematoxylin and eosin and imaged in order to construct a timeline of morphological development encompassing each embryonic stage, the hatchling, and the adult. Indirect immunofluorescence microscopy was used to assess the expression of genes associated with eye development, including Pax6.

Results : The parietal and pineal vesicle form from an evagination of the dorsal diencephalon during the period of embryo development concurrent with formation of the lens vesicle in the eye. Shortly after initial formation, the parietal (anterior) and pineal (posterior) vesicles separate. The dorsal aspect of the parietal vesicle gives rise to lens-like cells, and the ventral aspect of the vesicle gives rise to retinal-like cells. Cells in the surface ectoderm immediately adjacent to the vesicle develop into a corneal-like tissue. Pax6 is robustly expressed in the parietal lens epithelium and cornea; low levels of Pax6 are expressed in presumptive glial cells in the parietal retina.

Conclusions : The development of the parietal eye occurs in a series of morphogenic events similar to those expected of eye development. Differences in the histogenesis of the parietal eye compared to the lateral eye suggest a new pathway for lens induction. Further elucidating the specific roles of parietal eye regulatory networks could complement lateral eye studies to lead to better understanding of vertebrate eye formation.

This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.

 

A. sagrei parietal eye

A. sagrei parietal eye

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