Morphology and evolution of the snake cornea

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DOI

  • Mari-Ann Otkjaer Da Silva, Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 38, DK-2000, Frederiksberg, Denmark.
  • ,
  • Jacob Thorup Gade, Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 38, DK-2000, Frederiksberg, Denmark.
  • ,
  • Christian Damsgaard
  • Tobias Wang
  • Steffen Heegaard, Eye Pathology Section, Department of Pathology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark., Department of Ophthalmology, Rigshospitalet, University of Copenhagen, Glostrup, Denmark.
  • ,
  • Mads Frost Bertelsen, Center for Zoo and Wild Animal Health, Copenhagen Zoo, Roskildevej 38, DK-2000, Frederiksberg, Denmark.

To investigate whether the thickness of the cornea in snakes correlates with overall anatomy, habitat or daily activity pattern, we measured corneal thickness using optical coherence tomography scanning in 44 species from 14 families (214 specimens) in the collection at the Natural History Museum (Denmark). Specifically, we analyzed whether the thickness of the cornea varies among species in absolute terms and relative to morphometrics, such as body length, spectacle diameter, and spectacle thickness. Furthermore, we examined whether corneal thickness reflects adaptation to different habitats and/or daily activity patterns. The snakes were defined as arboreal (n = 8), terrestrial (n = 22), fossorial (n = 7), and aquatic (n = 7); 14 species were classified as diurnal and 30 as nocturnal. We reveal that the interspecific variation in corneal thickness is largely explained by differences in body size, but find a tendency towards thicker corneas in diurnal (313 ± 227 μm) compared to nocturnal species (205 ± 169 μm). Furthermore, arboreal snakes had the thickest corneas and fossorial snakes the thinnest. Our study shows that body length, habitat, and daily activity pattern could explain the interspecific variation in corneal morphology among snakes. This study provides a quantitative analysis of the evolution of the corneal morphology in snakes, and it presents baseline values of corneal thickness of multiple snake species. We speculate that the cornea likely plays a role in snake vision, despite the fact that results from previous studies suggest that the cornea in snakes is not relevant for vision (Sivak, Vision Research, 1977, 17, 293-298).

Original languageEnglish
JournalJournal of Morphology
Volume281
Issue2
Pages (from-to)240-249
Number of pages10
ISSN0362-2525
DOIs
Publication statusPublished - Feb 2020
Externally publishedYes

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