Chaetomorpha antennina

Thallus filamentous, rigid, caespitose, gregarious, forming dense brush-like tufts, 1.2-4(-12) cm long, dark green to bluishgreen. Filaments straight, 420-730-(900) mm diam. near tips tapering to 200 mm diam. near to the basal portion and 70 mm diam. close to the rhizoidal part. Cells cylindrical, 2-4 diameters long. Cell walls thick, striated (especially in basal cell), grayish or light brownish, slightly constricted at septations. Basal cell elongated to 4.5-12 mm long with annular constrictions near the base. Rhizoids fine, branched, 25-30 mm diam., 175-1000 mm long. Growing on rocky substrate (often in crevices and holes) in the upper to lower intertidal zone exposed to moderate and strong wave action.

Subtropical and tropical waters of Atlantic, Indian and Pacific Oceans.