David Ruales, Carlos ArturoVásquez Torres, Walter2012-04-092012-04-0920101794-4449http://hdl.handle.net/10567/138Abstract Introduction. The gills are, for the fish, the most important organ for the transportation and regulation of ionic and osmotic gradients, and for the balance acid-base, the excretion of nitrogen wastes and the metabolism of circulating hormones, becoming the center of the physiological responses to internal and environmental changes. Objective. To make a document to register the structure, the vascularization and the main cells of this ephitelium, and its relation with ionic transportation for maintaining its homeostasis, in order to sustain the role of the ionic regulation in the homeostasis of fish, keeping in mind that these physiological mechanisms can be a reason to fail or to succeed in the fish breeding activities. Selection criteria for the bibliography. Classic authors on the fish physiology field were revised, plus many articles produced from research works and revisions from the last ten years. These materials were published especially in English and Portuguese. Results. There is an unexplored field concerning the mechanisms that maintain the homeostasis in fish. The work for our species is yet to be done. The new molecular tools could help to elucidate the contributions of many membrane transportation processes to the acid-base balance regulation, to the ionic transportation and to the excretion of metabolites associated with these processes. Challenges. To integrate different disciplines in order to obtain a clear image of how gills work and how the processes mentioned before determine the well being of fish.esPecesPeces - BranquiasPeces - FisiologíaPeces - ExcreciónPeces - MorfologíaCorporación Universitaria LasallistaArticle