Transfer to sea water of euryhaline freshwater
fishes, results in the degeneration of the b-cell
through apoptosis and hypertrophy of the a-cell
(Pisam et al., ’87; Wendellar Bonga and van der
Meij, ’89). The a-cell is transformed into what is
recognized as the seawater chloride cell (CC). The
transformation consisted of an increase in the size
of the a-cell, density of the cytoplasm, number of
mitochondria, the tubular system network with a
tighter polygonal mesh size, and the apical
tubulovesicular system. A mitochondria-poor cell
type has been described by van der Heijden et al.
(’99) that possesses a well-developed tubular
system but has relatively few mitochondria. This
cell increases in frequency following seawater
acclimation and infrequently contacts the water.
No function was suggested for this cell type.