Meeting Abstract
51.6 Sunday, Jan. 5 11:30 Ocular histology of three south central Texas Eurycea, a novel system for the study of evolutionary developmental biology TOVAR, R.U.*; FREMAUX, B.P.; GARCIA, D.M.; Texas State University; Texas State University ; Texas State University r_t63@txstate.edu
The south central Texas Eurycea clade presents a continuum of morphologies unique to the tetrapod lineage. The Texas blind salamander (Eurycea rathbuni) with its reduced eyes and skin pigmentation exemplifies subterranean phenotypes. The San Marcos salamander (Eurycea nana) and the Barton Springs salamander (Eurycea sosorum) are epigean species, and exhibit well-developed eyes and full pigmentation. While external morphology suggests differing ocular anatomy and functionality between epigean and subterranean species, ocular histological descriptions have yet to be accomplished for E. nana and E. sosorum. The paucity of ocular histology warrants a holistic review of this novel clade and its potential as a new tetrapod model system for ocular studies. Herein we present the first ocular histological description of E. nana and E. sosorum with E. rathbuni for a comparative review. Adult specimen heads were donated by the San Marcos National Fish Hatchery Aquatic Research Center and preserved for cryosectioning. The sections were mounted and imaged using confocal microscopy via auto-fluorescence of the specimen. We observed well-developed retinal layers, cornea, iris, and lens in E. nana and E. sosorum. These results suggest the epigean species have the histological structures necessary for visual function. Reciprocally, E. rathbuni has vestigial eyes, including an undifferentiated cell mass covered by pigment epithelium suggesting non-functioning eyes. Interestingly, a prominent optic nerve was noted in the vestigial eye of E. rathbuni. Further research is needed to understand the functions of these structures. Knowledge of adult ocular histology is critical for future investigation of this novel system, with particular regard to their evolutionary developmental biology.
