MANTLE AND GILL FINE-STRUCTURE IN THE FRESH-WATER ASIATIC CLAM, CORBICULA-FLUMINEA (MULLER)

The epithelia of the main organs Likely to be involved in contaminant uptake, viz. mantle and gill were studied in the Asiatic clam Corbicul a fluminea as a base for future ecotoxicological studies. On its margi n, the mantle epithelium displays three folds separated by two grooves . The outer epithelium made of cubic cells, and the periostracal groov e are involved in the formation is composed of the shell, secreting cr ystals and the periostracal lamella respectively. In the median area, the inner epithelium is composed of three cell types: ordinary epithel ial cells, ciliated cells and mucocytes. The gill epithelium displays two structurally and functionally different areas: a respiratory area in the interlamellar chamber and, on the opposite side, a ciliated epi thelium. The respiratory epithelium is composed of thin pavement epith elial cells. The ciliated epithelium is made of different cell types: lateral ciliated epithelial cells, secretory cells, latero-frontal cil iated cells and ciliated frontal cells. The role of the secretory cell s is particularly discussed in relation to their structural similarity with lower vertebrate chloride cells (ionocytes) involved in iono- an d osmoregulation processes.