/roh"teuh feuhr/, n.any microscopic animal of the phylum (or class) Rotifera, found in fresh and salt waters, having one or more rings of cilia on the anterior end. Also called wheel animalcule.[1785-95; < NL; see ROTIFERA]
* * *Any of about 2,000 species of microscopic, multicellular, water-dwelling invertebrates constituting the class Rotifera, or Rotaria (phylum Aschelminthes; see worm).Currents created by the rotifer's corona (moving cilia arranged in a circle at the head) sweep bacteria, protozoans, and detritus into the mouth. Rotifers also eat larger items (other rotifers, crustaceans, algae). The muscular pharynx contains hard jaws. Body shape varies greatly among species. Rotifers are common in freshwater on all continents, but some live in saltwater. The species vary widely in mode of living: they may be free-living or parasitic, solitary or colonial, and free-swimming, crawling, or sedentary.Rotifer (Platyias quadricornis)Runk/Schoenberger from Grant Heilman
* * *also called wheel animalculeany of the approximately 2,000 species of microscopic, aquatic invertebrates that constitute the phylum Rotifera. Rotifers are so named because the circular arrangement of moving cilia (tiny hairlike structures) at the front end resembles a rotating wheel. Although common in freshwater on all continents, some species occur in salt water or brackish water, whereas others live in damp moss or lichens. Most are free-living; some are parasitic. Most live as individuals, but a few species form colonies. Most rotifers are only 0.1 to 0.5 mm (0.004 to 0.02 inch) long.The body may be spherical, flattened, bag-like, or wormlike. The body wall consists of a thin cuticle. Tufts of cilia at the anterior end make up the corona, which is used for feeding and locomotion. Small organisms are extracted as food from water currents created by the ciliated corona. Larger organisms, such as other rotifers, crustaceans, and algae, are also eaten. A mouth and digestive tract are usually present. The muscular pharynx, or mastax, contains hard, tiny jaws. Members of each species consist of an exact number of cells.In addition to the swimming rotifers, some (subclass Bdelloidea) loop along the bottom of ponds, alternately attaching the head and tail ends; others remain anchored by means of tubes or cases of jelly attached to the bottom.Modes of reproduction differ between species. Some species only reproduce parthenogenetically into females. Other species can reproduce both asexually and sexually, depending on environmental conditions. Males are smaller and less common in many species.
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