Polytoma

Polytoma
Scientific classification
Clade:	Viridiplantae
Division:	Chlorophyta
Class:	Chlorophyceae
Order:	Chlamydomonadales
Family:	Chlamydomonadaceae
Genus:	Polytoma; Ehrenberg
Species
	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.^[2] 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.^[3]

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.^[4]^[2]

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.^[3]

Phylogeny

As currently circumscribed, the genus Polytoma is polyphyletic, with its members grouping into two clades.^[5]

References

^ See the NCBI webpage on Polytoma. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19.
^ ^a ^b Bicudo, Carlos E. M.; Menezes, Mariângela (2006). Gêneros de Algas de Águas Continentais do Brasil: chave para identificação e descrições (2 ed.). RiMa Editora. p. 508. ISBN 857656064X.
^ ^a ^b Nakada, Takashi; Nozaki, Hisayoshi (2014). "Chapter 6. Flagellate Green Algae". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2 ed.). Elsevier Inc. ISBN 978-0-12-385876-4.
^ Smith, G. M. (1950) The Freshwater Algae of the United States, 2nd ed. New York: McGraw Hill, pp.78-79
^ Figueroa-Martinez, Francisco; Nedelcu, Aurora M.; Smith, David R.; Reyes-Prieto, Adrian (2017). "The Plastid Genome of Polytoma uvella is the Largest Known among Colorless Algae and Plants and Reflects Contrasting Evolutionary Paths to Nonphotosynthetic Lifestyles". Plant Physiology. 173 (2): 932–943. doi:10.1104/pp.16.01628. PMC 5291040.

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[1] See the NCBI webpage on Polytoma. Data extracted from the "NCBI taxonomy resources". National Center for Biotechnology Information. Retrieved 2007-03-19.

[Bicudo_and_Menezes2006-2] Bicudo, Carlos E. M.; Menezes, Mariângela (2006). Gêneros de Algas de Águas Continentais do Brasil: chave para identificação e descrições (2 ed.). RiMa Editora. p. 508. ISBN 857656064X.

[Nakada2014-3] Nakada, Takashi; Nozaki, Hisayoshi (2014). "Chapter 6. Flagellate Green Algae". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2 ed.). Elsevier Inc. ISBN 978-0-12-385876-4.

[4] Smith, G. M. (1950) The Freshwater Algae of the United States, 2nd ed. New York: McGraw Hill, pp.78-79

[5] Figueroa-Martinez, Francisco; Nedelcu, Aurora M.; Smith, David R.; Reyes-Prieto, Adrian (2017). "The Plastid Genome of Polytoma uvella is the Largest Known among Colorless Algae and Plants and Reflects Contrasting Evolutionary Paths to Nonphotosynthetic Lifestyles". Plant Physiology. 173 (2): 932–943. doi:10.1104/pp.16.01628. PMC 5291040.

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