Overview
The Oligohymenophorea are a large class of protozoa. There is typically a ventral groove containing the mouth and distinct oral cilia, separate from those of the body. These include a paroral membrane to the right of the mouth and membranelles, usually three in number, to its left. The cytopharynx is inconspicuous and never forms the complex cyrtos found in similar classes. Body cilia generally arise from monokinetids, with dikinetids occurring in limited distribution over part of the body.
In most groups the body cilia are uniform and often dense, while the oral cilia are inconspicuous and sometimes reduced, but among the peritrichs almost the opposite is the case. Members are widely distributed, and include many free-living (typically fresh-water, but many marine) and symbiotic forms. Most are microphagous, grazing on smaller organisms swept into the mouth by the cilia, but various other feeding habits occur. In one group, the astomes, the mouth and associated structures have been lost altogether.
The Oligoohymenophorea were first proposed in 1974 as one of three classes of ciliates, together with the Polyhymenophorea or spirotrichs and the now abandoned Kinetofragmophora. Since then the apostomes have been added, but otherwise its composition has remained relatively constant, with the main variations being the positions of the peniculids and plagiopylids.
Taxonomy
The Class Oligohymenophorea is further organized into finer groupings including:
- Subclass (6): Apostomatia · Astomatia · Hymenostomatia · Peniculia · Peritrichia · Scuticociliatia
- Infraclass (1): Pterygota
- Order (11): Apostomatida · Astomatida · Astomatophorida · Hymenostomatida · Mobilida · Peniculida · Philasterida · Pilisuctorida · Pleuronematida · Sessilida · Thigmotrichida
- Species: ZipcodeZoo has pages for 80 species and subspecies in the Class Oligohymenophorea.
Orders
Apostomatida
Astomatida
Astomatophorida
Hymenostomatida
The hymenostomes are an order of protozoa. Most are free-living in freshwater, such as the commonly studied genus Tetrahymena, but some are parasitic on fish or aquatic invertebrates. Among these is the important species Ichthyopthirius multifiliis, a common cause of death in aquaria and fish farms. [more]
Mobilida
Peniculida
The peniculids are an order of protozoa, including the well-known Paramecium and its close relatives. Most are relatively large, freshwater forms that feed on smaller organisms swept into the mouth. They have simple life cycles, and in many cases do not even form resting cysts. [more]
Philasterida
Pilisuctorida
Pleuronematida
Sessilida
Thigmotrichida
More info about the Order Thigmotrichida may be found here.
References
- Puytorac, P. de, A. Batisse, J. Bohatier; J.O. Corliss, G. Deroux, P. Didier; J. Dragesco, G. Fryd-Versavel, J. Grain, C.-A. Grolière, R. Hovasse, F. Iftode, M. Laval, M. Rogue, A. Savoie, and M. Tuffrau. (1974). Proposition d'une classification du phylum Ciliophora Doflein, 1901. Comptes Rendus de l'Académie de Sciences, Paris 278: 2799-2802.
Sources
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