The Desmidiaceae are one of four families of charophyte green algae in the order Desmidiales (desmids). Desmids in the family Desmidiaceae consist of single-celled (sometimes filamentous or colonial), microscopic green algae. Because they are highly symmetrical, attractive, and come in a diversity of forms, they are popular subjects for microscopists, both amateur and professional.

Within the desmids (Desmidiales), Desmidiaceae contains tens of genera and thousands of species, making it by far the largest family. Desmidiaceae includes some of the largest and most complex desmid genera, such as Micrasterias, Cosmarium, Staurastrum, and Euastrum.

Description

Desmids are single-celled (sometimes filamentous or colonial) algae, which are generally constricted in the middle, having two identical halves called semicells. The cell wall also consists of two halves. In apical view, the cells may be compressed (biradiate), three- or multi-angular (tri- or multiradiate), or circular (omniradiate). The cell wall is marked by having pores which penetrate all cell wall layers and contain a mucilaginous plug (called the pore fields). In addition to having pores, the cell wall may be covered in spines, pits ("scrobicles" or "scrobiculae"), lobes, or granules. Chloroplasts are axial or parietal.

Genera

Within the family Desmidiaceae, genera are delimited based on morphological characters such as the symmetry of the cells; whether the cells are solitary, filamentous, or colonial; the presence or absence of long processes or extensions; and the shape of the chloroplasts. However, most of these characters are highly homoplasious; therefore, many or even most genera are artificial and para- or polyphyletic.

Genera accepted by AlgaeBase were:

• Actinodontum – 3 species

• Actinotaenium – 66 species

• Allorgeia – 2 species

• Amscottia – 2 species

• Bambusina – 8 species

• Bourellyodesmus – 10 species

• Brachytheca – 2 species

• †Closterimopsis – 1 species

• Cosmarium – 1206 species

• Cosmocladium – 8 species

• Croasdalea – 1 species

• Cruciangulum – 1 species

• Desmidium – 25 species

• †Desmidopsis – 1 species

• Docidium – 22 species

• Euastridium – 3 species

• Euastrum – 358 species

• Groenbladia – 6 species

• Haplotaenium – 4 species

• Heimansia – 2 species

• Hyalotheca – 14 species

• Ichthyocercus – 6 species

• Ichthyodontum – 1 species

• Mateola – 1 species

• Micrasterias – 100 species

• Onychonema – 1 species

• Oocardium – 3 species

• Pachyphorium – 1 species

• Phymatodocis – 3 species

• Pleurotaeniopsis – 1 species

• Pleurotaenium – 89 species

• Prescottiella – 1 species

• Pseudomicrasterias – 2 species

• Sphaerozosma – 20 species

• Spinocosmarium – 2 species

• Spondylosium – 33 species

• Staurastrum – 788 species

• Staurodesmus – 87 species

• Streptonema – 3 species

• Teilingia – 9 species

• Tetmemorus – 10 species

• Triplastrum – 3 species

• Triploceras – 3 species

• Vincularia – 1 species

• Xanthidium – 128 species

References