Piermarini, P.M.*; Choe, K.P.; Evans, D.H.: Morphological and immunochemical properties of the urinary bladder in female Atlantic stingrays (Dasyatis sabina)

In vertebrates, urinary bladders serve as temporary storage organs for urine produced by the kidneys. Additionally, bladders are able to attenuate the final pH and ionic concentrations of urine before it is excreted. In elasmobranch fishes, the urinary bladder has been described in the little skate (Raja erinacea), where it is only found in females and has been implicated in the acidification of urine. The goal of this study was to describe the urinary bladder of another elasmobranch species, the Atlantic stingray (Dasyatis sabina), and determine if the bladder demonstrates immunochemical evidence of enzymes known to be important for acid/base and ion regulation. We found that female Atlantic stingrays have two bladders (one for each kidney) that accumulate urine from several collecting ducts. Histological observations revealed that the bladder is composed of an outer connective tissue/muscular layer and an inner cuboidal epithelium (urothelium) that lines the bladder lumen. The urothelium is immunoreactive for carbonic anhydrase, vacuolar-proton-ATPase, and Na⁺,K⁺-ATPase, suggesting that it may have a role in acid/base and ion regulation of the Atlantic stingray. Supported by EPA STAR Grant U-915419-01-0 (PMP), Sigma-Xi Grants-in-Aid of Research (KPC), and NSF Grant IBN-9604824 (DHE).