desmidiales

Desmids (Green Algae) - Micrasterias rotata

Desmids are microscopic fresh water algae with attractive forms. The species of the genus Micrasterias are well known for their beauty, in fact Micrasterias means “little star”. They occur in many biotopes around the globe and prefer nutrient-poor habitats.

The cell wall is composed of three layers impregnated with openings or pores and pectin spicules. Many species are phototropic and are capable of moving towards light by extruding a gelatinous substance through these pores.

Micrasterias rotata is  a rather large species (length 200 – 300 μm, width 190 – 270 μm). This one in the photo is undergoing cell division.  Desmids reproduce both sexually and asexually. Asexually, they reproduce by a simple division. Sexually, they reproduce either through conjugation, a means of exchanging nuclear material between two organisms, or by fusion (when two organisms fuse to form a single new organism). Spores are rare.

[Plantae - Charophyta - Zygnemophyceae - Desmidiales- Desmidiaceae - Micrasterias - M. rotata]

References: [1] - [2] - [3]

Photo credit: ©Wim Van Egmond

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Micrasterias

Commonly known as green alga, this unicellular organism’s nucleus sits on a narrow isthmus linking its two mirror image “semi-cells.” A single large, space-filling chloroplast is housed within each semi-cell.

Photos courtesy of Marek Miś.

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Green Algae, Desmids, Dividing- Reproduction of an Isogametic Species