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The hypotrichs are a group of ciliated
In older systems of classification, the term hypotrich comprised all ciliates possessing a relatively flattened body shape, strong cirri restricted to the ventral surface, and a large oral region (peristome) partially surrounded by an "adoral zone of membranelles". From a phylogenetic point of view, this historic grouping--which included both euplotid ciliates (such as '' Euplotes'' and '' Aspidisca''), and stichotrichian ciliates (such as ''
The same high-level taxa are used, without ranks, by Adl et al. in their "Revised Classification of Eukaryotes" of 201
File:Oxytricha hymenostoma - 160x (8999935961).jpg, ''Oxytricha'' sp.
File:Oxytricha chlorelligera - 400x (10403483023).jpg, A hypotrich, ventral view
File:Stichotricha secunda - 400x - Macronuclei (14994677881).jpg,
protozoa
Protozoa (singular: protozoan or protozoon; alternative plural: protozoans) are a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Histo ...
, common in fresh water, salt water, soil and moss. Hypotrichs possess compound ciliary organelles called " cirri," which are made up of thick tufts of cilia
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...
, sparsely distributed on the ventral surface of the cell. The multiple fused cilia which form a cirrus function together as a unit, enabling the organism to crawl along solid substrates such as submerged debris or sediments. Hypotrichs typically possess a large oral aperture, bordered on one side by a wreath or collar of membranelles (small membranous structures made up of fused cilia), forming an "adoral zone of membranelles," or AZM.
Classification
In older systems of classification, the term hypotrich comprised all ciliates possessing a relatively flattened body shape, strong cirri restricted to the ventral surface, and a large oral region (peristome) partially surrounded by an "adoral zone of membranelles". From a phylogenetic point of view, this historic grouping--which included both euplotid ciliates (such as '' Euplotes'' and '' Aspidisca''), and stichotrichian ciliates (such as ''Oxytricha
''Oxytricha'' is a genus of ciliates in the family Oxytrichidae.
Genomics
The draft macronuclear genome of ''Oxytricha trifallax'' was published in 2013.
Species
References
Spirotrichea
Ciliate genera
{{Ciliate-stub ...
'' and ''Urostyla'')--is paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be pa ...
. Any natural group, or clade
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...
, that contains both '' Euplotes'' and ''Oxytricha
''Oxytricha'' is a genus of ciliates in the family Oxytrichidae.
Genomics
The draft macronuclear genome of ''Oxytricha trifallax'' was published in 2013.
Species
References
Spirotrichea
Ciliate genera
{{Ciliate-stub ...
'' would also have to include many morphologically dissimilar spirotrich ciliates, such as the tintinnids and the oligotrichs.
In the classification system developed by Denis Lynn in collaboration with Eugene B. Small, the subclass Hypotrichia was restricted to euplotids and one small order of marine ciliates called Kiitrichida, while most of the traditional hypotrichs were placed in the subclass Stichotrichia. However, some prominent researchers—notably, the Austrian ciliatologist Helmut Berger—rejected Lynn's nomenclature, and continued to assign non-euplotid "hypotrich" ciliates, such as oxytrichids and urostyloids, to some variant of Friedrich von Stein's original order Hypotricha.
In their revised classification of the phylum Ciliophora, published in 2016, Gao et al. place the "stichotrichs" of Lynn & Small in the synonymous subclass Hypotrichia, and place all euplotid and discocephalid ciliates in the subclass EuplotiThe same high-level taxa are used, without ranks, by Adl et al. in their "Revised Classification of Eukaryotes" of 201
References
` {{Taxonbar, from=Q130515 Spirotrichea