Ocular ultrasonography of sea turtles
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Acta Veterinaria Scandinavica Open Access
RESEARCH
Ocular ultrasonography of sea turtles Caterina Muramoto1, Vinícius Cardoso‑Brito1, Ana Cláudia Raposo1, Thais Torres Pires2 and Arianne Pontes Oriá1*
Abstract Background: Environmental changes contribute to the development of ophthalmic diseases in sea turtles, but information on their eye biometrics is scarce. The aim of this study was to describe ophthalmic ultrasonographic features of four different sea turtle species; Caretta caretta (Loggerhead turtle; n = 10), Chelonia mydas (Green turtle; n = 8), Eretmochelys imbricata (Hawksbill turtle; n = 8) and Lepidochelys olivacea (Olive ridley; n = 6) under human care. Corneal thickness, scleral ossicle width and thickness, anterior chamber depth, axial length of the lens, vitreous cham‑ ber depth and axial globe length were measured by B-mode sonography with a linear transducer. Carapace size and animal weight were recorded. A sonographic description of the eye structures was established. Results: The four species presented an ovate eyeball, a relatively thin cornea, and a small-sized lens positioned ros‑ trally in the eye bulb, near the cornea, resulting in a shallow anterior chamber. The scleral ossicles did not prevent the evaluation of intraocular structures, even with a rotated eye or closed eyelids; image formation beyond the ossicles and measurements of all proposed structures were possible. B-mode sonography was easily performed in all animals studied. The sonographic characteristics of the eye were similar among the four species. Since there was a correlation between the size of the eye structures and the size of the individual, especially its carapace size, the differences found between E. imbricata and Caretta caretta are believed to be due to their overall difference in size. Conclusions: Sonography is a valuable tool in ophthalmic evaluation of these species. Only minor differences were found between the species in this study, reinforcing their phylogenetic proximity and their similar functions and habitats. Keywords: Caretta caretta, Chelonia mydas, Eretmochelys imbricate, Eye, Lepidochelys olivacea, Ultrasound Background Sea turtles have different methods for orientation and spatial localization [1], and vision is one of the main senses involved in environmental interactions, hunting and defence against predators [2–6]. The retina of these species changes throughout their lives to adapt to different visual stimuli, resulting from the various environments with which they are in contact, both terrestrial and pelagic, during the migration process [7]. Sea turtles can *Correspondence: [email protected] 1 School of Veterinary Medicine and Zootechny, Federal University of Bahia, Avenida Adhemar de Barros, 500, Ondina, Salvador, BA 40170‑110, Brazil Full list of author information is available at the end of the article
differentiate colours and, like other aquatic species, they have spherical lenses which are the main means of light refraction in water [8]. The sea turtle’s eye is proportionally sma
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