Encyclopedia > Litostomatea

  Article Content

Litostomatea

Litostomatea
Scientific classification
Kingdom:Protista
Phylum:Ciliophora
Class:Litostomatea
Typical orders
Subclass Haptoria[?]
    Haptorida
    Pleurostomatida
Subclass Trichostomatia[?]
    Vestibulifera
    Entodiniomorphida

The Litostomatea are a class of ciliate protozoa, divided into two groups, ranked as subclasses. The Haptoria[?] includes mostly carnivorous forms, for instance Didinium[?], which preys exclusively on the ciliate Paramecium. The Trichostomatia[?] are mostly endosymbionts in the digestive tracts of vertebrates. These include the species Balantidium coli[?], which is the only ciliate parasitic in humans.

The body cilia arise from monokinetids, which have an ultrastructural arrangement characteristic to the group. The mouth is apical or subapical. In trichostomes it lies in a depression, or vestibule, containing modified somatic cilia. In one order, the Entodiniomorphida, the cilia are arranged into tufts or bands, and may be packed together to form syncilia, resembling the membranelles and cirri of spirotrichs (with which they were originally classified) and other ciliates. However, no true compound cilia occur.

In haptorians the mouth is typically surrounded by a ring of coronal cilia, arising from dikinetids derived from the anterior of the body kineties, and a ring of characteristic extrusomes called toxicysts. These discharge on contact with prey, penetrating and immobilizing them, and beginning digestion. In some forms the mouth is formed only during feeding, and everts to assist in capture. The cytopharynx takes the form of a straight tube, supported by rods or nematodesmata, which dilates greatly during ingestion. This structure is called a rhabdos, and is functionally and structurally distnct from the cyrtos found in several other classes.



All Wikipedia text is available under the terms of the GNU Free Documentation License

 
  Search Encyclopedia

Search over one million articles, find something about almost anything!
 
 
  
  Featured Article
242

...     Contents 242 Centuries: 2nd century - 3rd century - 4th century Decades: 190s 200s 210s 220s 230s - 240s - 250s 260s 270s 280s 290s Years: 237 ...

 
 
 
This page was created in 62.9 ms