Bursaria (Protozoan) Videos

Bursaria organisms are large enough to be barely visible, and are characterized by a distinctive "big mouth" or cytostome, which they use to scoop up protozoan prey. Once it has entered the cavity, the prey organism is surrounded and enclosed by a digestive vacuole.

Bursaria belongs to the class Colpodea in the phylum Ciliophora; the ciliates, of which there are approximately 8,000 species, are generally considered to be the most evolved and complex of the protozoans. The cell surface is covered with hundreds of hairlike structures called cilia that are arranged in rows. The cilia beat in synchronized waves, propelling the organism through the water. Most ciliates possess an oral cavity, or cytostome, through which food enters the cell. In some ciliates, the cilia around the cytostome have become modified into sheets called membranelles, which create a feeding current and act as a sieve to trap food particles. Ciliates possess two types of nuclei, a large nucleus, or macronucleus, and one or more small nuclei, or micronuclei. Reproduction is primarily asexual, by binary fission, but sexual reproduction also occurs by conjugation, a process by which two organisms exchange nuclear material.