STRUCTURE OF GILL EPITHELIUM IN TRITURUS-VITTATUS LARVAE

The gill epithelium ultrastructure of the larval stage of the newt, Tr iturus vittatus, has been studied. Two layers can be distinguished: an outer layer and an inner layer. The outer layer is composed of four c ell types: pavement cells, ciliary cells, mitochondria-rich cells (MRC ) and round, granule-containing cells. Large numbers of vesicles conta ining PAS ((+)) material can be seen in the apical part of the pavemen t cells Their outer face is covered with short microvilli. The ciliary cells contain many mitochondria and their surface is adorned with cil ia. The mi tochondria-rich cells are fully packed with mitochondria. T hey are unique in having elaborate tubular membranous infoldings, whic h open on to the surface in a net-like arrangement of long, slender mi crovilli. Finally, the outer layer contains very few (29 cells in a 35 mm length tissue, or 0.8/1 mm) rounded, granule-containing cells. The se granules, of various sizes and shapes, are PAS ((-)) and contain el aborate Golgi figures. The inner layer is characterized by the presenc e of numerous, large Leydig cells; 19.56 cells/mm tissue. Finally, lar ge, germinative cells rich in tonofilaments are situated on the baseme nt membrane.