Mitochondria-rich cells in Antarctic fish gills

We used transmission and scanning electron microscopy and an antibody to th e inner mitochondrial membrane to study the presence and localisation of mi tochondria-rich cells in the gills of two Antarctic fishes, Chionodraco ham atus (Channichthyidae) and Trematomus bernacchii (Nototheniidae). The gener al morphology of the gills in the two species was slightly different: in T. bernacchii the filament and secondary lamellae were short and thicker, and mitochondria-rich cells were less numerous than in C. hamatus. In the two species the mitochondria-rich cells, distributed in the secondary and prima ry epithelium, were of the same morphological type, similar to the alpha-ch loride cells of temperate seawater teleosts. The study was carried out to c ompare the mitochondria-rich cells of Antarctic fishes to the chloride cell s of temperate marine teleosts. Immunolocalisation, using a specific antibo dy to the x-subunit of Na+/K+-ATPase, was observed in numerous epithelial c ells in the interlamellar epithelium and on the secondary lamellae, suggest ing an active sodium chloride secretion.