CYTON-II - A SUBTEGUMENTAL CELL-TYPE IN THE CERCARIA OF SCHISTOSOMA-MANSONI

In Schistosoma mansoni cercaria, an aggregate of subtegumental cells i s found in a small, dorsoanterior area of the body (middivision). Thes e cells are nestled between two laterally positioned flame cells and t he muscle that delimits the anterior end of the body, and the anterior end of the central ganglion. This highly amorphous cell type, designa ted as cyton II, has a heterochromatic nucleus and a cytoplasm that is elaborated into coarse, tortuous processes. Its cytoplasm contains ri bosomes, mitochondria, sparse amounts of endoplasmic reticulum, and tw o types of circular-to-oval concentric membranous bodies. One type has an electron-dense core and measures 200-250 nm on the short axis, and the other is completely membranous and measures 100-125 nm on the sho rt axis. The cell body of cyton II communicates with the tegument that covers a small, dorsoposterior area of the anterior organ (oral sucke r); however, we could not confirm a tegumental connection with the bod y division. When cercariae transform into schistosomules, the concentr ic membranous bodies of cyton II migrate into the anterior organ's teg ument via cytoplasmic processes of the cell. The major function of pre viously described cells that have similar membranous bodies is to supp ly additional membranes to the outer tegument during development into an adult worm. A multilaminated outer membrane is an adaptation to the survival of the schistosomule and adult worm in the bloodstream of th e vertebrate host (Hockley amd McLaren ['73]). The presence of membran ous bodies from cyton II in the tegument does not confirm that this ce ll type participates in the formation of multilaminated membranes. Its precise function remains to be determined. (C) 1995 Wiley-Liss, Inc.