Radiolaria are single-celled animals (ameboid protozoa) that inhabit the surface waters of the ocean - this example comes from the Caribbean. Only its skeleton remains here, magnified 1,000 times with a scanning electron microscope. The skeleton is composed of glass-like opaline silica. In life it is surrounded by cytoplasm and a cell wall. The spines reinforce leaf-like extensions of the cell called pseudopodia, which the radiolarian uses to feed and move along.