June 2020
Volume 61, Issue 7
Open Access
ARVO Annual Meeting Abstract  |   June 2020
A comparative study of the distribution and density of retinal ganglion cells and visual acuity in Bothrops snakes with differences in the habitat use
Author Affiliations & Notes
  • Christinia Patel
    University of Tennessee Health Science Center, Memphis, Tennessee, United States
    Minority Health International Research Training, Rhodes College, Memphis, Tennessee, United States
  • Juliana Tashiro
    Psychology Institute, University of Sao Paulo, Brazil
  • Einat Hauzman
    Psychology Institute, University of Sao Paulo, Brazil
  • Karina Banci
    Psychology Institute, University of Sao Paulo, Brazil
  • Malinda EC Fitzgerald
    Minority Health International Research Training, Rhodes College, Memphis, Tennessee, United States
  • Dora Fix Ventura
    Psychology Institute, University of Sao Paulo, Brazil
  • Footnotes
    Commercial Relationships   Christinia Patel, None; Juliana Tashiro, None; Einat Hauzman, None; Karina Banci, None; Malinda Fitzgerald, None; Dora Fix Ventura, None
  • Footnotes
    Support  Minority Health International Research Training grant
Investigative Ophthalmology & Visual Science June 2020, Vol.61, 4517. doi:
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      Christinia Patel, Juliana Tashiro, Einat Hauzman, Karina Banci, Malinda EC Fitzgerald, Dora Fix Ventura; A comparative study of the distribution and density of retinal ganglion cells and visual acuity in Bothrops snakes with differences in the habitat use. Invest. Ophthalmol. Vis. Sci. 2020;61(7):4517.

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

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Abstract

Purpose : The density and distribution of neurons in retinas of vertebrates are associated with specific behaviors and species ecology. The visual system of snakes has adaptations to the species’ habitats, circadian rhythm, and foraging strategies. A previous study revealed a ventral area centralis in a terrestrial snake and a visual streak in a close related arboreal species. In this study, we compared the distribution of ganglion cell layer (GCL) cells in retinas of Viperidae snakes from the genus Bothrops, with differences in the habitat use, namely the arboreal B. insularis, and the semi-arboreal species B. jararaca and B. sazimai.

Methods : Three individuals of each species were euthanized with Thionembutal (100 mg/kg). The eyes were enucleated and retinas were dissected and fixed in 4% paraformaldehyde. Retinas were wholemounted and Nissl stained. The density of GCL cells was estimated using a stereological approach with the Stereo Investigator software (MicroBrightField), and isodensity maps were obtained using OriginPro 8.5.1. Visual acuity values were estimated based on the peak density of GCL cells and the eyes focal length.

Results : We observed a poorly defined horizontal streak in retinas of the arboreal B. insularis, with higher density in the central retina, while in the semi-arboreal B. jararaca and B. sazimai there were no defined retinal specializations, and the peak cell densities were located in the temporal region. The mean cell density was 4,405 ± 735 cells/mm2 in B. insularis, 4,606 ± 335 cells/mm2 in B. sazimai, and 4,881 ± 746 cells/mm2 in B. jararaca. The estimated spatial resolutions were similar among the species and varied from 2.0 to 2.2 cycles per degree.

Conclusions : These findings reinforce the hypothesis that retinal specializations are associated with habitat use in snakes. A visual streak may assist in locomotion and hunting among branches, as indicated by the distribution of cells in B. insularis. On the other hand, peak GCL cell density in the temporal retina may facilitate striking behavior in the species that forage on the ground.

This is a 2020 ARVO Annual Meeting abstract.

 

Fig. 1. Distribution of GCL cells in Bothrops snakes. The isodensity values in cells/mm2 are represented by the grayscale. The white circles indicate the optic nerves. D, dorsal; T, temporal. Scale bars: 4 mm.

Fig. 1. Distribution of GCL cells in Bothrops snakes. The isodensity values in cells/mm2 are represented by the grayscale. The white circles indicate the optic nerves. D, dorsal; T, temporal. Scale bars: 4 mm.

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