Short-term transformation and long-term replacement of branchial chloride cells in killifish transferred from seawater to freshwater, revealed by morphofunctional observations and a newly established 'time-differential double fluorescent staining' technique.
Short- and long-term responses to direct transfer from seawater to freshwater were examined in gill chloride cells of killifish, which developed distinct freshwater- and seawater-type chloride cells in the respective environments. In a short-term response within 24 h after transfer, seawater-type chloride cells forming a pit structure on the apical surface were transformed into freshwater-type cells equipped with developed microvilli on the flat or projecting apical membrane, via the intermediate type. The transformation process was accompanied by the disappearance of apically located Cl- channel (cystic fibrosis transmembrane conductance regulator) and neighboring accessory cells. Chloride cell replacement was also examined as a long-term adaptation to freshwater transfer, using a newly established 'time-differential double fluorescent staining (TDS)' technique. In the TDS technique, in vivo labeling of chloride cells was performed on two separate days, using two distinguishable mitochondria-specific fluorescent probes. For 3 days after freshwater transfer, 14.7% of seawater-type cells were replaced with newly differentiated freshwater-type cells, whereas these ratios of chloride cell replacement were much lower (1.2% and 1.8%) in seawater- and freshwater-maintained groups, respectively. In consequence, following direct transfer of killifish from seawater to freshwater, seawater-type chloride cells were transformed morphologically and functionally into freshwater-type cells as a short-term response, followed by the promotion of chloride cell replacement as a long-term response.
Katoh
Fumi
F
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo 113-8657, Japan. fkatoh@marine.fs.a.u-tokyo.ac.jp
Kaneko
Toyoji
T
D000064:Acclimatization / Q000502:physiology*; D000818:Animals; D015153:Blotting, Western; D018118:Chloride Channels / Q000502:physiology*; D005618:Fresh Water; D023781:Fundulidae / Q000502:physiology*; D005880:Gills / Q000166:cytology* / Q000502:physiology* / Q000648:ultrastructure; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D012623:Seawater; D013997:Time Factors
D018118:Chloride Channels