Avaliação qualitativa da lágrima dos tetrápodes

Abstract

Tear is a complex fluid involved in nourishment, stability, protection and removal of foreign bodies from ocular surface. There are studies regarding its components and dynamics for mammalian species; however, the knowledge about this fluid in other species is limited. The evolutive process for adaptation and environmental influences may inducted changes on vertebrate tears. In addition, qualitative and quantitative differences can occur, even in animals phylogenetically related. Therefore, the objective of this research was to perform qualitative quantitative evaluation of tetrapod tears (reptiles, birds and mammals), using unpublished methodologies for wild animals. The protein profile and biochemical composition of the tear of reptiles, birds and mammals, present in different ecological niches, were evaluated comparatively with blood serum and human tear, and it was obtained that the tear of the animals contained the same compounds present in the tear human and blood serum in different proportions. Together with this finding, it was attributed that the phylogenetic proximity, diet and environment, the latter in a significant way, influence on the tear components. From these results, some species were selected because of their notorious differences in the electrophoretic profile for the proteomic investigation of the tear, as hawk (Rupornis magnirostris), caiman (Caiman latirostris) and sea turtle (Caretta caretta). In addition, the glycoproteins present in the tear of the hawk and alligator were described, where the results show a higher frequency of this compound for birds, and that possibly the glycoproteins allow greater diversity to the lacrimal fluid. The proteins found, as well as their ontogenic characteristics, have demonstrated that the tear composition can be derived from the environmental conditions and lifestyles of the animals, being able to adapt to the complex adaptation of the species. Besides, even before the most primitive metabolic processes, there is an maintenance in the stability mechanisms of tears. So, the tear fluid pervades what is described for mammals and is a fluid with high adaptation power. It has roles in maintaining ocular surface homeostasis and consequently visual function.