ESTUDO ULTRA-ESTRUTURAL DA BEXIGA NATATÓRIA DE PIRARUCU (Arapaima gigas)

Abstract

Pirarucu (Arapaima gigas), osteoglossoid fish from the Amazon basin in extinction process, comes rising up great economic interest. Due to not very knowledge on histologic and ultrastructural details of this species and because the swimbladder functions is a very important respiratory organ for this fish, an ultrastructural study on its swimbladder was performed. Fragments of several areas of the swimbladder were collected and processed for observation in a transmission electronic microscope. The internal surface of the organ was showed covered by prismatic epithelial cells with countless continuous and intertwined blood capillaries, being also covered by fine cytoplasmic projections of the adjacent epithelial cells. Just below, connective tissue was found, being more cellular in the dorsal portion and more fibrous in the ventral portion of the organ. In the dorsal portion, this tissue joins the swimbladder to the kidney, and in the ventral portion it is continuous to the thick layer of smooth muscle. Externally, this portion is covered by simple pavimentous epithelium. The ultrastructural characteristics found in the swimbladder are suitable with the functions of air exchange suggested for the organ.