The hymenostomes are an order of ciliate protozoa. Most are free-living in freshwater, such as the commonly studied genus Tetrahymena, but some are parasitic on fish or aquatic invertebrates.[1] Among these is the important species Ichthyophthirius multifiliis, a common cause of death in aquaria and fish farms.

Hymenostome
Tetrahymena thermophila
Scientific classification Edit this classification
Domain: Eukaryota
Clade: Diaphoretickes
Clade: SAR
Clade: Alveolata
Phylum: Ciliophora
Class: Oligohymenophorea
Subclass: Hymenostomatia
Delage & Hérouard, 1896
Order: Hymenostomatida
Delage & Hérouard 1896
Typical families

Suborder Tetrahymenina
    Curimostomatidae
    Tetrahymenidae
    Turaniellidae
    Glaucomidae
Suborder Ophryoglenina
    Ichthyopthiriidae
    Ophryoglenidae
Suborder Peniculina

The hymenostomes are fairly typical members of the Oligohymenophorea. Their body cilia are mostly uniform, sometimes with a few long caudal cilia, and arise from monokinetids or from dikinetids at the anterior. The oral cilia are in general distinctly tetrahymenal, with three membranelles and a paroral membrane, which corresponds only to the middle segment of the tripartite membranes found in certain scuticociliates. Mouth formation during cell division usually begins next to a postoral kinety.

The hymenostomes were first defined by Delage & Hérouard in 1896. Initially the scuticociliates and peniculids were included, then later treated as separate orders of a subclass Hymenostomatia, to which the astomes are sometimes added. More recently each of these groups tends to be treated as a separate subclass.[2]

References

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  1. ^ Golini, Victor I.; Corliss, John O. (January 1981). "A Note on the Occurrence of the Hymenostome Ciliate Tetrahymena in Chironomid Larvae (Diptera: Chironomidae) from the Laurentian Great Lakes". Transactions of the American Microscopical Society. 100 (1): 89. doi:10.2307/3225789. JSTOR 3225789.
  2. ^ John O Corliss (2016-04-20). The Ciliated Protozoa: Characterization, Classification and Guide to the Literature. Pergamon. pp. 112–124. ISBN 9781483154176. Retrieved 17 January 2018.