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Einat Hauzman, Daniela Maria Oliveira Bonci, Dora Fix Ventura; Visual ecology of snakes: comparative study of the density and distribution of retinal neurons in diurnal and nocturnal species.. Invest. Ophthalmol. Vis. Sci. 2016;57(12):4667. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
This study aimed to compare the density and distribution of photoreceptors and ganglion cell layer (GCL) cells in retinas of 20 species of snakes, from the Colubridae and Dipsadidae families and correlate the results with the activity pattern of the species.
The snakes were collected at Butantan Institute and euthanized with a lethal dose of thiopental. The eyes were enucleated and the retinas dissected (n=86). We used immunohistochemistry and Nissl staining techniques in wholemount retinas to quantify the density of photoreceptor and GCL cells. The spatial resolving power was estimated based on the peak density of GCL cells and posterior nodal distance of the eyes. We compared the average density of cell of diurnal and nocturnal snakes and applied t tests for independent samples.
Diurnal snakes had lower density of photoreceptors compared to nocturnal (t = 6,18, p < 0,0001), but higher density of GCL cells (t = 2,88, p = 0,007) and spatial resolving power (t = -4,484, p < 0,0001) (Table; Figure). The distribution of cells had differences among diurnal and nocturnal species: diurnal snakes had a horizontal streak and nocturnal had an area centralis. The location of the area centralis varied according to the species habitat: in the dorsal retina for fossorial snakes (Atractus sp), in the ventral region for arboreal (Dipsas sp) and in the central region for terrestrial (O. guibei).
The results of this study point to the strong influence of the circadian rhythm of snakes in the density and distribution of retinal neurons. The region of peak density is associated with the species habitat and ecology.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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