Ciliates Classes : Ciliata, Holotricha

Ciliates (Class Ciliata) – Protozoans

These protozoans have many cilia and nuclei of two sizes. Because the mastigophoran Opalina also has many flagella (or cilia), it is the nuclei that act as the criterion and establish the true ciliates as a distinct group. Other features include a kinety.

Holotrichs (Subclass Holotricha)

This group is regarded as more primitive than the other subclasses for there is a lack of development in the peristomial membranelles. A feature that cuts across all other complications and simplifications of structure is the way the cilia are fused to form accessory organelles in the funnel-shaped cytopharynx or cell mouth. It is characteristic of this subclass that no fused structures are present and the mouth is plainly open. Typically the body (somatic).

The system of fibrils and granules for coordinating the cilia, characteristic cross-wise fission, and a charac teristic form of sexual reproduction called conjugation. The range of forms exhibited in this class is so great that it suggests a very long independent evolutionary history.

While it is relatively easy to place a protozoan as a ciliate it is often quite difficult to determine its order unless the genus is already known, because elaborations and fusion of some cilia, are often accompanied by the loss of others, has occurred in each order. This type of parallel evolution produces genera that are superficially similar.

The only sure method of identification is the application of one of the silver line staining techniques, in which it is possible to show portions of the kinety system and so obtain the necessary characterization upon which their taxonomy is based. But this is a method not readily or easily performed.

The habitats are various: parasitic, commensal, and free-living species are found in many orders. The degree of morphological specialization in some of the spirotrichs is noteworthy as an example of elaboration in a single cell: adaptation to unusual habitats such as the interstitial spaces in the sand has to lead to great elongation of up to 5 mm. in some species, while some free-living freshwater species are only 15μ long.

Subclasses, Orders, and suborders of Class Ciliata

  1. Ciliates (Class Ciliata): Subclass Holotricha
  2. Gymnostomes ( Gymnostomatida), Rhabdophorina, Cyrtophorina, Suctorians (Order Suctorida),
  3. Hymenostomes, Hymenostomatida, Peritrichs

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