The name Xanthidium is a diminutive of Xanthium, and presumably refers to its spines, reminiscent of the prickly fruits of Xanthium.[3]
Description
Xanthidium exists as symmetrical single cells. Cells are deeply constricted, forming two halves called semicells; they are rectangular, rounded, or polygonal in front view, flattened. The angles are usually drawn out into spines, which are typically paired and sometimes branched. Semicells often have a protuberance or additional spine in the center of the semicell. Cells have two or many axile chloroplasts which fill the cell.[4][5] A notable exception is the species Xanthidium tumidum, formerly placed in the genus Staurastrum as Staurastrum tumidum. Morphologically it is triangular in cross section (unlike other species, which are flattened in cross section). Its placement in this genus is due to molecular data.[6]
Identification
Species identification of Xanthidium depends on the shape of the cell, cell wall ornamentation, and location and number of the spines. However, some species such as Xanthidium antilopaeum are notoriously polymorphic.[7]
Habitat
Like other desmids, most species of Xanthidium prefer acidic waters.[8]
^Rabenhorst, L. (1853). Kryptogamen-Flora von Sachsen, Ober-Lausitz, Thüringen und Nord-Böhmen, mit Berücksichtigung der benachbarten Länder: erste Abtheilung: Algen im weitesten Sinne, Leber und Laubmoose. Leipzig: Verlag von Eduard Kummer. pp. i–xx, 1–653.
^Hall, John D.; McCourt, Richard M. (2014). "Chapter 9. Conjugating Green Algae Including Desmids". In Wehr, John D.; Sheath, Robert G.; Kociolek, J. Patrick (eds.). Freshwater Algae of North America: Ecology and Classification (2 ed.). Elsevier Inc. ISBN978-0-12-385876-4.
^Stastny, Jan; Skaloud, Pavel; Langenbach, Dorothee; Nemjova, Katarina; Neustupa, Jiri (2013). "Polyphasic evaluation of Xanthidium antilopaeum and Xanthidium cristatum (Zygnematophyceae, Streptophyta) species complex". Journal of Phycology. 49 (2): 401–416. doi:10.1111/jpy.12051. PMID27008526. S2CID23597409.
^Prescott, G. W.; Bicudo, C. E. M.; Vinyard, W. C. (1982). A Synopsis of North American Desmids. Part II: Desmidiaceae: Placodermae. Section 4. Lincoln: University of Nebraska Press. p. 700.
