Mastigophora

(invertebrate zoology) A superclass of the Protozoa characterized by possession of flagella.

A superclass of the Protozoa also known as the Flagellata. The common morphological flagellate type is spherical to cylindrical on an anteroposterior axis. Despite their common morphological plan, based on the flagellum as a means of locomotion, Flagellata are very diverse in shape, colony formation, internal structure, external shell or test, color, physiology, reproduction, and choice of environment.

The Mastigophora exhibit marked plantlike characteristics, so that texts and references in botany always treat at least some of them. Some workers include all colorless flagellates in the algae; however, flagellates display many distinctly animal features and sometimes are treated as Protozoa. Thus, flagellates are regarded as a link between the plant and animal kingdoms. See also Phytamastigophorea; Zoomastigophorea.

Mastigophora possess one common feature, locomotion by means of one or more whiplike protoplasmic extrusions termed flagella. The flagellate body is typically monaxial and elongate to some degree. Cells are practically spherical in Monas, but ovoid, cordiform, pyriform, fusiform, acicular, tubular, or flattened cells are more common. Flattened species typically glide along a surface rather than swim. A particular shape is normally maintained by Ochromonas, whereas Mastigamoeba and some others form pseudopodia, and certain species (Euglena agilis) undergo frequent distortions termed euglenoid or metabolic changes of shape.

Structurally the flagellate cell is not simple. The cytoplasm is sometimes quite vacuolated (Collodictyon or Trepomonas) and occasionally colored, although color is generally confined to chromatophores when these are present. One or more contractile vacuoles may be located near the flagellar base.

Most flagellates are single-celled but colony formation is frequent. Cells may be naked (Oicomonas), enclosed in a thick cellulose cell wall or pellicle (Euglena spirogyra), or in a chitinous, calcareous, or silicious test, the lorica or shell (Trachelomonas, Distephanus speculum).

Flagellates adjust to wide ranges of pH, osmotic pressure, light, and temperature but optima are found upon investigation. Some flagellate species occur in both fresh and sea water, but cannot be transferred directly from fresh to sea water. Almost any aqueous ecological niche contains Flagellata.

Flagellata are near the base of the food pyramid, probably next to bacteria. Their varied synthetic abilities, fast reproductive rate, and huge numbers in both fresh and salt water compensate for their usual small size. The oceanic blooms which kill fish and other animals are principally flagellates, but green flagellates reaerate polluted water. They often cause tastes and odors in potable water, but they readily attack organic matter in natural water as do bacteria, They include many parasites dangerous to humans and animals and are themselves frequently parasitized. See also Protozoa.