{{Short description|Genus of single-celled organisms}} {{Automatic taxobox | image = The ciliate Frontonia sp.jpg | image_caption = ''Frontonia'' sp., specimen is digesting cyanobacteria, the mouth (cytostome) is at the bottom right. | taxon = Frontonia | authority = Ehrenberg, 1838 | subdivision_ranks = Species | subdivision = See text }}
'''''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,<ref>{{cite journal |last1=Dias |first1=Roberto Júnio P. |last2=D'Agosto |first2=Marta |title=Feeding behavior of ''Frontonia leucas'' (Ehrenberg) (Protozoa, Ciliophora, Hymenostomatida) under different environmental conditions in a lotic system |journal=Revista Brasileira de Zoologia |date=September 2006 |volume=23 |issue=3 |pages=758–763 |doi=10.1590/S0101-81752006000300021 |doi-access=free }}</ref> and even, in some circumstances, members of their own species.<ref>{{cite journal |last1=Devi |first1=R. Vimala |title=Cannibalism in ''Frontonia leucas'' Ehr. |journal=The Journal of Protozoology |date=August 1964 |volume=11 |issue=3 |pages=304–307 |doi=10.1111/j.1550-7408.1964.tb01758.x }}</ref> In bacteria-rich saprobic conditions, ''Frontonia leucas'' can live as a facultative bacterivore.<ref>{{cite journal |last1=Dias |first1=Roberto Júnio P. |last2=D'Agosto |first2=Marta |title=Feeding behavior of ''Frontonia leucas'' (Ehrenberg) (Protozoa, Ciliophora, Hymenostomatida) under different environmental conditions in a lotic system |journal=Revista Brasileira de Zoologia |date=September 2006 |volume=23 |issue=3 |pages=758–763 |doi=10.1590/S0101-81752006000300021 |doi-access=free }}</ref>
''Frontonia'' are widely dispersed, and members of the genus can be found in marine and freshwater environments on every continent.<ref>{{cite journal |doi=10.1111/j.1574-6941.2006.00259.x |title=Ciliate biogeography in Antarctic and Arctic freshwater ecosystems: Endemism or global distribution of species? |year=2007 |last1=Petz |first1=Wolfgang |last2=Valbonesi |first2=Alessandro |last3=Schiftner |first3=Uwe |last4=Quesada |first4=Antonio |last5=Cynan Ellis-Evans |first5=J. |journal=FEMS Microbiology Ecology |volume=59 |issue=2 |pages=396–408 |pmid=17313584 |s2cid=13117002 |doi-access=free }}</ref><ref>{{cite journal |last1=Long |first1=Hongan |last2=Song |first2=Weibo |last3=Al-Rasheid |first3=Khaled A. S. |last4=Wang |first4=Yangang |last5=Yi |first5=Zhenzhen |last6=Al-Quraishy |first6=Saleh A. |last7=Lin |first7=Xiaofeng |last8=Al-Farraj |first8=Saleh A. |title=Taxonomic studies on three marine species of ''Frontonia'' from northern China: ''F. didieri'' n. sp., ''F. multinucleata'' n. sp. and ''F. tchibisovae'' Burkovsky, 1970 (Ciliophora: Peniculida) |journal=Zootaxa |date=23 January 2008 |volume=1687 |issue=1 |pages=35 |doi=10.11646/zootaxa.1687.1.2 }}</ref>
==Appearance and characteristics== thumb|170px|left|Frontonia leucas, by V. Schewiakoff, 1889 thumb|''Frontonia'' sp. ''Frontonia'' species vary in length from 50 to 600 micrometres.<ref>Patterson, D.J. Free-Living Freshwater Protozoa: A Colour Guide. Manson, 1992,1996. p. 133. {{ISBN|1-874545-40-5}}</ref> 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.<ref>Carey, Philip G., Marine interstitial ciliates: an illustrated key. Chapman and Hall, 1992, {{ISBN|978-0-412-40610-2}} p. 129</ref> 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),<ref>{{cite journal |last1=Gil |first1=Rosario |title=Cortical fine structure of ''Frontonia leucas'' (Ciliata: Holotricha) |journal=Transactions of the American Microscopical Society |date=1981 |volume=100 |issue=4 |pages=373–383 |doi=10.2307/3226150 |jstor=3226150 }}</ref> and may expand during feeding to as much as two-thirds of the cell's length.<ref>{{cite journal |last1=Goldsmith |first1=William M. |title=The process of ingestion in the ciliate, ''Frontonia'' |journal=Journal of Experimental Zoology |date=October 1922 |volume=36 |issue=3 |pages=332–351 |doi=10.1002/jez.1400360305 |url=https://zenodo.org/record/1426888 }}</ref>
The cytoplasm of some species, such as ''Frontonia atra'' and ''Frontonia acuminata'', can be darkly pigmented.
==Classification== The genus ''Frontonia'', created by C. G. Ehrenberg in 1838, includes some thirty named and described species.<ref>{{cite journal |last1=Long |first1=Hongan |last2=Song |first2=Weibo |last3=Gong |first3=Jun |last4=Hu |first4=Xiaozhong |last5=Ma |first5=Honggang |last6=Zhu |first6=Mingzhuang |last7=Wang |first7=Mei |title=''Frontonia lynni'' n. sp., a new marine ciliate (Protozoa, Ciliophora, Hymenostomatida) from Qingdao, China |journal=Zootaxa |date=3 June 2005 |volume=1003 |issue=1 |pages=57 |doi=10.11646/zootaxa.1003.1.4 }}</ref>
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.<ref>{{cite journal |id={{NAID|10029826287}} |last1=Gao |first1=Shan |last2=Chen |first2=Zi-Gui |last3=Shao |first3=Chen |last4=Long |first4=Hong-An |last5=Al-Rasheid |first5=Khaled A. S. |last6=Song |first6=Wei-Bo |title=Reconsideration of the phylogenetic position of ''Frontonia''-related Peniculia (Ciliophora, Protozoa) inferred from the small subunit ribosomal RNA gene sequences |journal=Acta Protozoologica |date=1 March 2008 |volume=47 |issue=1 }}</ref>
==Image gallery== <gallery> Image:Frontonia leucas.jpg Image:Frontonia vernalis -- from Ehrenberg.jpg </gallery>
==Video gallery== <gallery> File:Frontonia ingesting a diatom.ogg|''Frontonia leucas'' ingesting a diatom File:Frontonia atra.ogg|''Frontonia atra'' has symbiotic bacteria in its cytoplasm File:Frontonia leucas.ogv|''Frontonia leucas'', radiating canals around contractile vacuole File:Frontonia vernalis.ogv|''Frontonia vernalis'' carries symbiotic algae in its cytoplasm </gallery>
==List of accepted species names== {{columns-list|colwidth=25em|1= * ''Frontonia aberrans'' Dragesco, 1960 * ''Frontonia acuminata'' (Ehrenberg, 1834) Bütschli, 1889 * ''Frontonia acuta'' Fromentel, 1876 * ''Frontonia acutissima'' Dumas, 1930 * ''Frontonia alba'' Fromentel, 1876 * ''Frontonia algivora'' Kahl, 1931 * ''Frontonia ambigua'' Dragesco, 1972 * ''Frontonia angusta Kahl'', 1931 * ''Frontonia arenaria Kahl'', 1933 * ''Frontonia atra'' (Ehrenberg, 1834) Bütschli, 1889 * ''Frontonia branchiostomae'' Codreanu, 1928 * ''Frontonia canadensis'' * ''Frontonia caneti'' Dragesco, 1960 * ''Frontonia curva'' Fromentel, 1876 * ''Frontonia cypraea'' Zacharias, 1904 * ''Frontonia depressa'' (Stokes, 1886) Kahl, 1931 * ''Frontonia didieri'' Long, Song, AL-Rasheid, Wang, Yi, Al-Quraishy, Lin & AL-Farraj, 2008 * ''Frontonia elliptica'' Beardsley, 1902 * ''Frontonia frigida'' Petz, Song & Wilbert, 1995 * ''Frontonia fusca'' Quennerstedt, 1869 * ''Frontonia lacrimula'' Dumas, 1930 * ''Frontonia leucas'' (Ehrenberg, 1834) Ehrenberg, 1838 * ''Frontonia longaria'' Dumas, 1930 * ''Frontonia lurida Blochmann'', 1895 * ''Frontonia lynni'' Long, Song, Gong, Hu, Ma, Zhu & Wang, 2005 * ''Frontonia macrostoma'' Srámek-Husek, 1957 * ''Frontonia magnistoma'' Foissner, 1987 * ''Frontonia marina'' Fabre-Domergue, 1891 * ''Frontonia marisalbi'' Burkovsky, 1970 * ''Frontonia microstoma'' Kahl, 1931 * ''Frontonia minuta'' Dragesco, 1970 * ''Frontonia multinucleata'' Long, Song, AL-Rasheid, Wang, Yi, Al-Quraishy, Lin & AL-Farraj, 2008 * ''Frontonia nassuloides'' Lepsi, 1926 * ''Frontonia nigricans'' Penard, 1922 * ''Frontonia obtusa'' * ''Frontonia ocularis'' Bullington, 1940 * ''Frontonia ovalis'' Fromentel, 1876 * ''Frontonia parameciiformis'' Wenzel, 1953 * ''Frontonia parva'' Fromentel, 1876 * ''Frontonia parvula'' Penard, 1922 * ''Frontonia perna'' Fromentel, 1876 * ''Frontonia piriformis'' Dumas, 1930 * ''Frontonia roqueae'' Dragesco, 1970 * ''Frontonia rostrata'' Fromentel, 1876 * ''Frontonia rotunda'' Gelei, 1954 * ''Frontonia salmastra'' Dragesco & Dragesco-Kernéis, 1986 * ''Frontonia schaeferi Bullington'', 1940 * ''Frontonia solea Foissner'', 1987 * ''Frontonia tanganyikae'' Dragesco & Dragesco-Kernéis, 1991 * ''Frontonia subtropica'' * ''Frontonia tchibisovae'' Burkovsky, 1970 * ''Frontonia terricola'' Foissner, 1987 * ''Frontonia undulata'' Dumas, 1929 * ''Frontonia vacuolata'' Dragesco, 1960 * ''Frontonia vernalis'' (Ehrenberg, 1834) Kahl, 1931 * ''Frontonia vesiculosa'' Cunha, 1913 }}
==References== {{Reflist|30em}}
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Category:Oligohymenophorea Category:Ciliate genera Category:Taxa named by Christian Gottfried Ehrenberg Category:Articles containing video clips