Xanthidium Antilopaeum
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''Xanthidium'' is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of
green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...
, specifically of the
Desmidiaceae The Desmidiaceae are one of four family (biology), families of Charophyta, charophyte green algae in the order (biology), order Desmidiales (desmids).See the National Center for Biotechnology Information, NCBI]webpage on Desmidiaceae Data extrac ...
. The name ''Xanthidium'' is a
diminutive A diminutive is a word obtained by modifying a root word to convey a slighter degree of its root meaning, either to convey the smallness of the object or quality named, or to convey a sense of intimacy or endearment, and sometimes to belittle s ...
of ''
Xanthium ''Xanthium'' (cocklebur) is a genus of flowering plants in the tribe Heliantheae within the family Asteraceae, native to the Americas and eastern Asia and some parts of south Asia. Description Cockleburs are coarse, herbaceous annual plants grow ...
'', and presumably refers to its spines, reminiscent of the prickly fruits of ''Xanthium.


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
chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...
s which fill the cell. A notable exception is the species '' Xanthidium tumidum'', formerly placed in the genus ''
Staurastrum ''Staurastrum'' is a large genus of desmids (Desmidiaceae), a group of green algae closely related to the land plants (Embryophyta). Members of this genus are microscopic and found in freshwater habitats around the world. The name ''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.


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.


Habitat

Like other desmids, most species of ''Xanthidium'' prefer acidic waters.


References


External links

*
AlgaTerra database

Index Nominum Genericorum
Desmidiaceae Charophyta genera {{green algae-stub