Arraias de água doce: o animal e sua história ambiental

Abstract

The general objective of the present study was to evaluate the historical context of freshwater stingrays and the morphohistological aspects of the integument of the stingray Potamotrygon rex. Therefore, we carried out a contextualized bibliographic review using the CAPES database, Sciverse Hub, Sciverse Science Direct, Sciverse Scopus, Scirus and Pubmed. The results showed that the environment forces them to diversify and adapt, and stingrays are an example of adaptation and tolerance to freshwater environments. During the adaptive process, these animals underwent several modifications to adapt to an environment with the least amount of salt. Among them are inability to retain urea, lack of salt excretion, as the rectal gland is reduced, and changes in receptor cells (Lorenzini ampoules). Another organ that had to adapt to the new type of environment was the integument. Stingray skin can be considered the first line of defense against pathogens, in addition to participating in the regulation of several physiological processes, such as ionic and osmotic regulation, locomotion and reproduction. Therefore, epidermal cells perform several specific functions, however they are poorly studied. In this sense, we also investigated the morphology of the dorsum and sting cells of the freshwater stingray P. rex. We found that the back and the stinger have cells that are specialized in the production of specific substances. By using histochemical techniques, we found the coexistence of acidic and neutral mucopolysaccharides in the back tegument, as well as large protein reservoirs whose specific function is well applied in the literature.