Osmoregulation and ionoregulation in the mangrove killifish, Kryptolebias marmoratus, during air exposure
The euryhaline amphibious mangrove killifish, 'Kryptolebias marmoratus', is tolerant of variable salinities and air exposure. I hypothesized that in air, the gills (if functional) would have a reduced role in exchange with the external environment and the skin would play an important role in osmo- and ionoregulation. The surface area of the gills decreased after 9 days in air regardless of substratum salinity and exposure to terrestrial environments containing high salt resulted in an increase in the surface area of skin ionocytes, whereas the number of mucous cells declined. Radiolabeled water and ion flux occurred across the skin in air. Cl - and water homeostasis, but not Na+, were achieved in air. Overall, the findings from this study suggest that the skin is a site of osmo- and ionoregulation during extended terrestrial periods in ' K. marmoratus' and reversible morphological changes to the skin and gills may promote osmotic and ionic balance.