Mitochondria-rich cells in gills and skin of an African lungfish, Protopterus annectens

We used scanning electron microscopy, the vital dye DASPEI and an antibody to the inner mitochondrial membrane to study the presence and localisation of mitochondria-rich cells in the gills and skin (opercular, dorsal and ven tral) of the lungfish Protoprerus annectens in its free-swimming conditions and at the beginning of aestivation. In the free-swimming period, the gill s were short and thick and the pavement cells were extremely large (30-40 m um) The mitochondria-rich cells, which were distributed in the secondary an d primary epithelium, occurred as two morphologically different types, i.e. elongated and oval, similar to the alpha and beta chloride cells of fresh water teleosts. In the skin, only one type of mitochondria-rich cells was f ound, resembling the a chloride cells. All the mitochondria-rich cells dist ributed in the gills and skin were labelled with anti Ca2+-ATPase serum ind icating the possible uptake of Ca2+ at freshwater chloride cell level. At t he start of aestivation, the skin and gills were covered by a thick layer o f mucus and the epithelium of the gills was reduced. The mitochondria-rich cells.