Pithophora Wittrock, 1877

Lectotype species: Pithophora kewensis Wittrock

Currently accepted name for the type species: Pithophora roettleri (Roth) Wittrock

Original publication: Wittrock, V.B. (1877). On the development and systematic arrangement of the Pithophoraceae, a new order of algae. Nova Acta Regiae Societatis Scientiarum Upsaliensis Ser. 3, extra ordinem(Editum 1877, Art 19): 1-80, VI plates.

Type designated in: Boedeker, C., O'Kelly, C.J., Star, W. & Leliaert, F. (2012). Molecular phylogeny and taxonomy of the Aegagropila clade (Cladophorales, Ulvophyceae), including the description of Aegagropilopsis gen. nov. and Pseudocladophora gen. nov. Journal of Phycology 48(3): 808-825.

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Description: Light green to dark greenish brown branched filaments, typically free-floating as wool-like masses in stagnant warm-temperate to tropical waters, but also reported from moist soil. Fertile filaments are easily identified by characteristic akinetes. Mainly first order branches, sometimes second order branches, branches inserted subterminally and with delayed cross wall formation. Branching pattern typically falcate, sometimes opposite. Cells are long, slender, and cylindrical, with a diameter of 40–200 ?m and thin walls without layers. The length:width ratio is 5–20–(100), and can be very variable even within individuals. Terminal cells are conical and rounded, or can form non-septate secondary rhizoids, termed helicoids, which can be like a tendril, or like a two-pronged fork, or like a small number of claws or a coralloid haptere. Helicoids can attach the thallus to other filaments, or more rarely to the sediment. Secondary rhizoids other than the terminal helicoids are not formed. Akinetes short and swollen, with dark cell contents, mostly single, frequently alternated in a regular manner with long, cylindrical cells. Akinetes are formed by most of the cell contents of a vegetative cell migrating to the upper end of the cell, followed by transverse division leaving a short akinete and much longer vegetative cell with very little cytoplasm. Akinetes can be intercalary and terminal, sometimes twin akinetes are formed. Akinetes germinate into a new branch, or after resting phase into a new thallus. Germination of akinetes and development of a new thallus by transverse division into 2 daughter cells, one developing into a short primary rhizoid, the other into a branched filament. Rarely, the primary rhizoid can be multicellular, and even form short side branches and akinetes. The other mode of vegetative reproduction is by fragmentation, sexual reproduction unknown. Pronounced phenotypic plasticity in the few morphological characters has led to an inflation in the number of described species (Ernst 1908, Mothes 1930, Fott 1971, Pankow & Täuscher 1980, Boedeker et al. 2012). More than 40 taxa of Pithophora have been described, with akinete features as the most important diagnostic characters. However, culture studies have shown that akinete formation and germination is controlled by a wide range of environmental conditions, that the size of akinetes is dependent on age, that akinete and branch formation are the same reversible process and that terminal rhizoid formation is inducible as a wounding response (Brand 1904, Ernst 1908, Mothes 1930, Agrawal 1986, Stevens & Neilson 1987). The little genetic variation among Pithophora samples of different origin and morphologies hints at the existence of a single widespread, plastic species (Boedeker et al. 2012). The frequent formation of desiccation-resistant akinetes in Pithophora implies high dispersal potential, facilitating gene flow and reducing the potential for local adaptation and speciation. Pithophora can exhibit prolific growth in nutrient-rich environments and the resulting mass developments can be local nuisances (Entwisle & Price 1992, Lembi 2003). Surface mats are typically floating at the surface during warm periods and high photosynthetic activity, disturbance of these mats by high wind or heavy rain events may cause them to temporarily sink to the bottom, and only to return to the surface after several days.

Information contributed by: Skaloud et al. (2018: 186).. The most recent alteration to this page was made on 2018-03-16 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Škaloud, P., Rindi, F., Boedeker, C. & Leliaert, F. (2018). Süßwasserflora von Mitteleuropa. Freshwater flora of central Europe: Chlorophyta V: Ulvophyceae. Vol. 13 pp. [i]-vii, [1]-288, 182 figures. Berlin: Springer Spektrum.

Comments: Pithophora is common in tropical and temperate regions throughout the world (and introduced into Britain). P. oedogonia is tolerant of temperatures > 30 C and low light irradiances, an advantage for mat-forming alga in shallow littoral areas of lakes. Nitrate has been idfentified as the major factor limiting growth in such environments. Cell walls contain chitin, as well as cellulose, providing an explanation for the distinctive mode of branching

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Contributors
Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=43501

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 16 March 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 23 November 2024