Nassophorea
Encyclopedia
The Nassophorea are a class of ciliate protozoa. Members are free-living, usually in freshwater but also in marine and soil environments. The mouth is anterior ventral and leads to a curved cytopharynx supported by a prominent palisade of rods or nematodesmata, forming a structure called a cyrtos or nasse, typical of this and a few other classes. When present, extrusome
s take the form of fibrous trichocysts. Cilia are usually monokinetids, but vary from order to order.
The Synhymeniida and Nassulida have mostly uniform cilia arising from monokinetids. Among the former, and a few members of the latter, there is a series of small polykinetids running from below the mouth to the left side of the body and sometimes almost circling the cell, called a frange or synhymenium. Other forms only have three oral membranelle
s, sometimes extending out of the oral cavity, with or without a paroral membrane. These are usually medium in size, sometimes larger, and cylinder shaped.
The Microthoracida typically have three or more oral membranelles, with at least a vestige of the paroral membrane occurring during cell division. The body cilia are sparse, and often arise from dikinetids, with cirrus-like polykinetids occurring in the marine genus Discotricha. These are usually small and ellipsoid or crescent shaped, with the right side of the body curved outward, and generally have a rigid pellicle.
As first defined by Eugene Small and Denis Lynn in 1981, the Nassophorea also included the peniculid
s and, in a separate subclass, the hypotrich
s. More recent schemes restore these to their earlier positions, leaving this group a relatively small collection of less well-known forms.
Extrusome
Extrusomes are membrane-bound structures in some eukaryotes which, under certain conditions, discharge their contents outside the cell. There are a variety of different types, probably not homologous, and serving various functions....
s take the form of fibrous trichocysts. Cilia are usually monokinetids, but vary from order to order.
The Synhymeniida and Nassulida have mostly uniform cilia arising from monokinetids. Among the former, and a few members of the latter, there is a series of small polykinetids running from below the mouth to the left side of the body and sometimes almost circling the cell, called a frange or synhymenium. Other forms only have three oral membranelle
Membranelle
Membranelles are structures found around the mouth, or cytostome, in ciliate protists. They are typically arranged in series, to form an "adoral zone of membranelles," or AZM, on the left side of the buccal cavity . The membranelles are made up of kinetosomes arranged in groups to make up...
s, sometimes extending out of the oral cavity, with or without a paroral membrane. These are usually medium in size, sometimes larger, and cylinder shaped.
The Microthoracida typically have three or more oral membranelles, with at least a vestige of the paroral membrane occurring during cell division. The body cilia are sparse, and often arise from dikinetids, with cirrus-like polykinetids occurring in the marine genus Discotricha. These are usually small and ellipsoid or crescent shaped, with the right side of the body curved outward, and generally have a rigid pellicle.
As first defined by Eugene Small and Denis Lynn in 1981, the Nassophorea also included the peniculid
Peniculid
The peniculids are an order of ciliate 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.Typically...
s and, in a separate subclass, the hypotrich
Hypotrich
The hypotrichs are a group of ciliate protozoa, included among the spirotrichs. Most are oval in shape, with a rigid pellicle, and have cirri distributed in isolated tufts on the ventral surface of the cell. Some also have dorsal cilia, which function as sensory bristles. Euplotes and Aspidisca...
s. More recent schemes restore these to their earlier positions, leaving this group a relatively small collection of less well-known forms.