Polytoma

{{Short description|Genus of algae}} {{About|the genus of green algae|the orchid|Bletilla}} {{Automatic taxobox | image = Polytoma-path2383-292.png | taxon = Polytoma | authority = Ehrenberg | type_species = ''Polytoma uvella'' | type_species_authority = Ehrenberg<ref name=AlgaeBase>{{AlgaeBase genus | id= 44236 | name=Ehrenberg | access-date=2024-11-29 }}</ref> | subdivision_ranks = Species | subdivision_ref = <ref>See the NCBI [https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=40525 webpage on Polytoma]. Data extracted from the {{cite web | url=https://ftp.ncbi.nih.gov/pub/taxonomy/ | title=NCBI taxonomy resources | publisher=National Center for Biotechnology Information | access-date=2007-03-19}}</ref> | subdivision = * ''P. anomale'' * ''P. difficile'' * ''P. ellipticum'' * ''P. mirum'' * ''P. obtusum'' * ''P. oviforme'' * ''P. uvella'' * ''P. sp. strain ATCC 30963'' * ''P. sp. strain SAG 195.80'' * ''P. sp. strain SAG 62-20'' }}

'''''Polytoma''''' is a genus of flagellates in the family Chlamydomonadaceae. Algae are similar to the genus ''Chlamydomonas'', but lack chlorophyll and are colorless.<ref name=Bicudo_and_Menezes2006/> Although they are not photosynthetic, they are grouped with the green algae because they are phylogenetically related to, and derived from, flagellate green algae.

''Polytoma'' species are found in waters rich in organic matter.<ref name=Nakada2014/>

==Description== ''Polytoma'' is a genus of colorless, free-living chlorophytes similar in form to ''Chlamydomonas'' but lacking chlorophyll. Two flagella emanate from the anterior papilla of the cell, and cells have two contractile vacuoles at the flagellar base. The cell body can be spherical, ellipsoid, ovoid, or kidney-shaped. ''Polytoma'' possesses a leukoplast in place of a chloroplast, in which many starch grains are concentrated; there are typically no pyrenoids. Since they lack photosynthetic capability, ''Polytoma'' species are entirely saprotrophic, obtaining nutrients from decaying organic matter. Some species possess an eyespot apparatus (stigma) in the anterior portion of the leucoplast, but in others this organelle is absent.<ref>Smith, G. M. (1950) The Freshwater Algae of the United States, 2nd ed. New York: McGraw Hill, pp.78-79</ref><ref name=Bicudo_and_Menezes2006>{{cite book | title= Gêneros de Algas de Águas Continentais do Brasil: chave para identificação e descrições | edition=2 | year=2006 | first1=Carlos E. M. |last1=Bicudo | first2=Mariângela | last2= Menezes | publisher= RiMa Editora | pages=508 | isbn= 857656064X }}</ref>

Asexual reproduction occurs when the parent cell divides into four zoospores, while in the parent cell wall. Sexual reproduction can be isogamous, anisogamous, or oogamous.<ref name=Nakada2014>{{cite book |editor-first1=John D.|editor-last1=Wehr|editor-first2=Robert G.|editor-last2=Sheath|editor-first3=J. Patrick|editor-last3=Kociolek |date= 2014 |edition=2 |title= Freshwater Algae of North America: Ecology and Classification |last1= Nakada|first1=Takashi| last2=Nozaki |first2=Hisayoshi |chapter= Chapter 6. Flagellate Green Algae |url= |location= |publisher= Elsevier Inc. |page=|isbn=978-0-12-385876-4 }}</ref>

==Phylogeny== As currently circumscribed, the genus ''Polytoma'' is polyphyletic, with its members grouping into two clades.<ref>{{cite journal|doi=10.1104/pp.16.01628 |title=The Plastid Genome of ''Polytoma uvella'' is the Largest Known among Colorless Algae and Plants and Reflects Contrasting Evolutionary Paths to Nonphotosynthetic Lifestyles |date=2017 |last1=Figueroa-Martinez |first1=Francisco |last2=Nedelcu |first2=Aurora M. |last3=Smith |first3=David R. |last4=Reyes-Prieto |first4=Adrian |journal=Plant Physiology |volume=173 |issue=2 |pages=932–943 |pmc=5291040 }}</ref>

==References== {{Reflist|1}}

Category:Chlamydomonadales genera Category:Chlamydomonadaceae Category:Taxa named by Christian Gottfried Ehrenberg