Abstract
To compare tear electrolytes and tear crystallization patterns in birds and reptiles, tears were sampled by Schirmer tear test from 10 animals each of Ara ararauna, Amazona aestiva, Tyto alba, Rupornis magnirostris, Chelonoidis carbonaria, and Caiman latirostris, and 5 of Caretta caretta. The aliquots were pooled to assess concentrations of total protein, chloride, phosphorus, iron, sodium, potassium, calcium, and urea. For the tear ferning test, samples of each species were observed under a polarized light microscope at room temperature and humidity. Crystallization patterns were graded according Rolando and Masmali scales. There was more total protein and urea in owl and sea turtle tears, respectively, than in the other animals tested. Electrolyte balance was similar for all species, with higher sodium, chloride, and iron. In birds, Rolando-scale grades of tear crystallization patterns ranged from I to II, and from 0 to 2 using the Masmali scale; in reptiles, grades were II to IV (Rolando) and 2 to 4 (Masmali). Crystallization arrangements of some species had higher scores, as caimans and sea turtles, possibly due to different the tear composition. Marine and lacustrine species presented higher. The ionic balance of lacrimal fluids of birds and reptiles was similar to that in humans, with higher values of sodium and chloride. However, a similar tear composition did not influence the crystal morphology. Crystallization classification suggested that higher grades and types are due to the different microelements present in the tears of wild species.
Highlights
The tear film is a complex fluid that covers the ocular surface, serving as the interface between the eye and the environment [1]
We examined 40 birds, 10 animals each of the species: Ara ararauna, Amazona aestiva, Tyto alba, Rupornis magnirostris, and 25 reptiles: 10 Chelonoidis carbonaria, 10 Caiman latirostris, and 5 Caretta caretta, all healthy adults from a triage center of wild animals (CETAS, Salvador, Brazil), a commercial breeder (Mister Cayman R, Maceió, Brazil), and a conservation center (TAMAR Project, Mata de São João, Brazil)
Aerial and terrestrial species obtained the lowest grading for Rolando and Masmali scales, the crystallization pattern was well differentiated, highlighting Ara ararauna tears with a uniform crystallization and Chelonoidis carbonaria tears presenting large spaces between the crystals (Figure 4)
Summary
The tear film is a complex fluid that covers the ocular surface, serving as the interface between the eye and the environment [1]. The main functions of the tear film are related to its interaction with the corneal epithelium, including lubrication, nutrition, metabolite removal, protection, and stability of the ocular surface [2, 3]. These functions stem from the diversity of its components, and it is characterized in vertebrates by the presence of lipids, water, proteins, and electrolytes [3, 4]. Tears are synthesized from the secretory lacrimal glands, goblet cells, and epithelial cells in the cornea and conjunctiva [5]. Secreted lacrimal ions have been described in mammals, resulting from
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