Phylum Actinopoda. Classes Polycystina and Phaeodaria (Radiolaria)

BOLTOVSKOY, DEMETRIO; ANDERSON O. R

Handbook of Protoctista

Jones and Bartlett Publishers

Lugar: USA; Año: 2010;

General Characteristics The Actinopoda comprise four protist groups (Polycystina, Phaeodaria, Acantharia and Heliozoa) characterized by the possession of axopodia – long and slender cytoplasmic projections supported by a rigid central rod that protrude radially from the cell (Fig. 1). Axopodia support a web-like network of sticky cytoplasmic strands that aid in the capture of prey. Most Polycystina and Phaeodaria (often jointly referred to as Radiolaria) have a siliceous skeleton. Both groups are exclusively marine and planktonic. All Phaeodaria are solitary, but Polycystina include some colonial forms. Single cells vary in size from below 40 µm to almost 2 mm (Phaeodaria are usually larger than Polycystina), but colonies may exceptionally be as long as 3 m (Swanberg, 1979).