LIN, L.Y.; HORNG, J.L.; KATOH, F.; KANEKO, T.; KUNKEL, J.; LIN, H. C.; HWANG, P. P.; Institute of Zoology, Academia Sinica, Taiwan, ROC; Institute of Zoology, Academia Sinica, Taiwan, ROC; Department of Biological Sciences, University of Alberta, Canada; Department of Aquatic Bioscience, University of Tokyo, Japan; Department of Biology, University of Massachusetts Amherst; Department of Biology, Tunghai University, Taiwan, ROC; Institute of Zoology, Academia Sinica, Taiwan, ROC; : LOCALIZATION OF H⁺ PUMP AND CARBONIC ANHYDRASE IN SKIN OF DEVELOPING ZEBRAFISH (DENIO RERIO) LARVAE

As in other vertebrates, fish must maintain homeostasis of intra- and extracellular pH. Because of the constraints of living in an aquatic environment, these animals must utilize strategies different from those of terrestrial animals for the acid-base regulation. In adult fishes, the gill epithelium is the primary site for the acid-base regulation. However, how do fish conduct acid-base regulation in developing, gill-less, larval stage is still unknown. V-type H⁺-ATPase (H⁺ pump) and carbonic anhydrase (CA) have been found in the gill epithelium of several species of fish and are thought to drive H⁺ excretion in gills. In this study, immunocytochemistry was used to investigate the distribution of H⁺ pump and CA in skin of developing zebrafish larva. Results show that both H⁺ pump and CA are localized in keratinocytes, which covering the most surface of the larvae. Among the keratinocytes, a type of cell displays strong H⁺ pump expression. This cell type was further identified as a type of ionocyte, which shares similar function and structure of the mitochondria-rich cells in fish gill, frog skin, and mammalian kidney. The H⁺ excreting activities in these cell types were also examined with electrophysiological technique, ion-selective vibrating probe.