A light and electron microscopic study of a new species of centroheliozoon, Chlamydaster fimbriatus.

The centroheliozoon Chlamydaster fimbriatus n.sp. has been studied in culture by light and electron microscopy. The cell body is surrounded by a fimbriated mucus envelope through which axopods extend. Each cell contains two or three contractile vacuoles and an eccentrically located nucleus with a single nucleolus. The cells have typical centroheliozoan characteristics such as a centroplast with a trilamellate disc, mitochondria with ribbon-like cristae, ball-and-cone kinetocysts, and a peripheral lacunar system. The axopodial axonemes possess a single hexagon of six microtubules. The genus is defined to include only centroheliozoa with a mucus coat. C. fimbriatus differs from the only other species recognized in this genus (C. laciniatus and C. sterni) in its size and number of arms. This is the first ultrastructural account of a species of the genus Chlamydaster.