A new type of cell in the larval epidermis of the green toad, Bufo viridis viridis

The flank skin of the premetamorphic stage of the green toad, Bufo viridis viridis, was studied by transmission electron microscopy. The skin was typically larval amphibian, made up of a highly fibrous and vascular dermis to the inside and a highly cellular epidermis to the outside with a distinct basal lamina separating the two layers. The epidermis is three-cells thick. The epidermal cells, mostly keratinocytes, are closely packed together and are attached to each other through desmosomes and interdigitations. The basal keratinocytes are anchored to the basal lamina through hemidesmosomes. In addition to the keratinocytes, some other types of cells known in the amphibian larval skin were found. These cells include mucus-secreting, mitochondria-rich cells, Merkle cells and flask cells. Anew type of cells, the dark cells, are described in this paper. The dark cell rests on the basal lamina. It is a ramified cell with a number of cytoplasmic processes intervening in between the keratinocytes. The cytoplasm is strikingly dark and rich with polysomes and granular endoplasmic reticulum.