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Vol. 50 No. 1, 2011
Morphological and Ion-Transporting Plasticity of Branchial Mitochondrion-Rich Cells in the Euryhaline Spotted Green Pufferfish, Tetraodon nigroviridis
Cheng-Hao Tang1 and Tsung-Han Lee1,2,*
1Department of Life Sciences, National Chung-Hsing University, Taichung 402, Taiwan
2Department of Biological Science and Technology, China Medical University, Taichung 404, Taiwan
Cheng-Hao Tang and Tsung-Han Lee (2011) Morphological characteristics and chloride regulatory functions of gill mitochondrion-rich (MR) cells of the pufferfish (Tetraodon nigroviridis) were investigated in this study, because T. nigroviridis
are widely used in studies of fish osmoregulation. In scanning electron
micrographs, the apical membrane structures of MR cells could be
distinguished into 3 phenotypes of flat, intermediate-indentation, and
concave-hole. The apical surfaces of most MR cells were flat with
microvilli in fresh water (FW)-acclimated pufferfish, whereas most
apical surfaces of MR cells were concave to form holes in brackish
water (BW) and seawater (SW)- acclimated pufferfish. Observed changes
in the proportion of the intermediate indentation type suggested that
when transferred from FW to BW or SW, pufferfish MR cells were
transformed from the flat type into the concave-hole type via different
stages of the intermediate indentation type. Meanwhile, no significant
difference in cell size and density of gill MR cells were found in
pufferfish acclimated to various salinities. To compare the
ion-transporting functions of MR cells, both the chloride test and
double immunofluorescent staining of Na+/K+-ATPase
(NKA) and the chloride-secreting channel, cystic fibrosis transmembrane
conductance regulator (CFTR), were examined. The CFTR was present in
the apical membrane of NKA-immunoreactive cells in gills of
SW-acclimated pufferfish, but completely disappeared in FW-acclimated
fish. Moreover, the chloride test directly demonstrated the chloride
secretion function of concave-hole MR cells. Taken together, our
findings suggested that different types of MR cells in pufferfish gills
expressed various iontransport proteins to conduct distinct functions
necessary for salinity acclimation of this euryhaline species.
Key words: Spotted green pufferfish, Tetraodon nigroviridis, Mitochondrion-rich cells, Cystic fibrosis transmembrane conductance regulator, Na+/K+-ATPase.
*Correspondence: E-mail:thlee@dragon.nchu.edu.tw
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