Frontonia | |
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Frontonia sp., specimen is digesting cyanobacteria, the mouth (cytostome) is at the bottom right. | |
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Genus: | Frontonia Ehrenberg, 1838 |
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Frontonia is a genus of free-living unicellular ciliate protists, belonging to the order Peniculida. As Peniculids, the Frontonia are closely related to members of the genus Paramecium . However, whereas Paramecia are mainly bacterivores, Frontonia are capable of ingesting large prey such as diatoms, filamentous algae, testate amoebas, [1] and even, in some circumstances, members of their own species. [2] In bacteria-rich saprobic conditions, Frontonia leucas can live as a facultative bacterivore. [3]
Frontonia are widely dispersed, and members of the genus can be found in marine and freshwater environments on every continent. [4] [5]
Frontonia species vary in length from 50 to 600 micrometres. [6] Cell bodies are typically ovoid or elongate, and somewhat flattened from back to front. They are flexible, uniformly ciliated, and usually surrounded by trichocysts. The small oral aperture is pear-shaped, and located in the anterior half of the cell. [7] Along the left side of the opening there are three membranelles, and the right has a single paroral membrane. The mouth is supported by inconspicuous microtubular rods (nematodesmata), [8] and may expand during feeding to as much as two-thirds of the cell's length. [9]
The cytoplasm of some species, such as Frontonia atra and Frontonia acuminata, can be darkly pigmented.
The genus Frontonia, created by C. G. Ehrenberg in 1838, includes some thirty named and described species. [10]
In 2008, analysis of small subunit rRNA gene sequences confirmed the close relationship of several members of the genus: Frontonia leucas,F. vernalis,F. tchibisovae,F. lynni. However, Frontonia didieri was found to be related more closely to a species from another genus, Apofrontonia dohrni. This result calls into question the monophyly of the genus Frontonia, and also casts doubt on the morphological criteria used to distinguish Apofrontonia from it. [11]
Blepharisma is a genus of unicellular ciliate protists found in fresh and salt water. The group includes about 40 accepted species, and many sub-varieties and strains. While species vary considerably in size and shape, most are easily identified by their red or pinkish color, which is caused by granules of the pigment blepharismin.
Stentor, sometimes called trumpet animalcules, are a genus of filter-feeding, heterotrophic ciliates, representative of the heterotrichs. They are usually horn-shaped, and reach lengths of two millimeters; as such, they are among the largest known extant unicellular organisms. They reproduce asexually through binary fission.
Spirostomum is a genus of ciliated protists in the class Heterotrichea. It is known for being very contractile. Having been first identified by Christian Gottfried Ehrenberg in 1834, further research has identified eight additional true morphospecies. This bacterivore genus mainly lives in the sediment deposits at the bottom of various aquatic habitats, and members possess rquA genes that could be responsible for their ability to survive in these hypoxic and anoxic environments. They are identifiable by their relatively large tubular/flat vermiform bodies. Their life cycle consists of a growth stage, in which they mature, and asexual and sexual reproduction stages. Some species are model organisms for studies on human pathogenic bacteria, while others are sensitive and accurate bioindicators for toxic substances.
Nassula is a genus of unicellular ciliates, belonging to the class Nassophorea. Like other members of the class, Nassula possesses a basket-like feeding apparatus made up of cytopharyngeal rods (nematodesmata), which are themselves composed of closely packed microtubules. Nassula use this structure to ingest filamentous cyanobacteria, drawing individual strands of blue-green algae through the cytopharynx and into the body of the cell, where they are digested. As the algae are broken down, they can take on a variety of bright colours, which give Nassula a distinctive, variegated appearance under the microscope.
The ciliates are a group of alveolates characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group and are variously used in swimming, crawling, attachment, feeding, and sensation.
Lacrymaria is a genus of ciliates. Its best known species is the "Tear of Swan", Lacrymaria olor.
Climacostomum is a genus of unicellular ciliates, belonging to the class Heterotrichea.
Dileptus is a genus of unicellular ciliates in the class Litostomatea. Species of Dileptus occur in fresh and salt water, as well as mosses and soils. Most are aggressive predators equipped with long, mobile proboscides lined with toxic extrusomes, with which they stun smaller organisms before consuming them. Thirteen species and subspecies of Dileptus are currently recognized.
Pseudomonilicaryon anser is a species of unicellular ciliates in the family Dileptidae, also known under the names Dileptus anser and Dileptus cygnus. The species is common in fresh water ponds, stagnant pools, mosses and soils.
Colpidium colpoda are free-living ciliates commonly found in many freshwater environments including streams, rivers, lakes and ponds across the world. Colpidium colpoda is also frequently found inhabiting wastewater treatment plants. This species is used as an indicator of water quality and waste treatment plant performance.
Condylostoma is a genus of unicellular ciliate protists, belonging to the class Heterotrichea.
Remanella is a genus of karyorelict ciliates, belonging to family Loxodidae. Whereas Remanella inhabits brackish and marine waters, Loxodes – the other loxodid genus – is a freshwater taxon.
Geleiidae is a family of karyorelict ciliates. It is sometimes synonymized with family Aveliidae.
Armophorea is a class of ciliates in the subphylum Intramacronucleata. . It was first resolved in 2004 and comprises three orders: Metopida, Clevelandellida, and Armophorida. Previously members of this class were thought to be heterotrichs because of similarities in morphology, most notably a characteristic dense arrangement of cilia surrounding their oral structures. However, the development of genetic tools and subsequent incorporation of DNA sequence information has led to major revisions in the evolutionary relationships of many protists, including ciliates. Metopids, clevelandellids, and armophorids were grouped into this class based on similarities in their small subunit rRNA sequences, making them one of two so-called "riboclasses" of ciliates, however, recent analyses suggest that Armophorida may not be related to the other two orders.
Tracheloraphis is a genus of ciliates in the family Trachelocercidae.
Parablepharismea is a class of free-living marine and brackish anaerobic ciliates that form a major clade of obligate anaerobes within the SAL group, together with the classes Muranotrichea and Armophorea.
Halteria, sometimes referred to as the jumping oligotrich, is a genus of common planktonic ciliates that are found in many freshwater environments. Halteria are easy to locate due to their abundance and distinctive behaviour with observations of Halteria potentially dating back to the 17th century and the discovery of microorganisms. Over time more has been established about their morphology and behavior, which has led to many changes in terms of classification.
Trachelocercidae is a family of ciliates in the class Karyorelictea.
Holosticha is a genus of littoral ciliates.
Anteholosticha is a genus of hypotrich, a group of protists.