Micrasterias

Micrasterias furcata Ralfs 1848

Micrasterias is occurring exclusively in freshwater genus of ornamental algae ( Desmidiales ) with about 40 species. They were elected by the Phycology Section of the German Botanical Society for the alga of 2008.

Features

Micrasterias are unicellular, unbegeißelte green algae. The cells are large and flattened in side view they appear spindle-shaped. A central constriction, the sinus, the cells are divided into two symmetrical halves. The half-cells are divided by notches further, first in a vertex and two lateral lobes. The side lobes are further divided into lobes, second to fourth order. Therefore, the cells appear star-shaped. On the rag frequently sitting pin-like cell wall projections.

The nucleus is colorless and is located in the bridge ( isthmus ) between the two halves. Each half- cell has a large flat chloroplasts with several pyrenoids. The shape of the chloroplasts corresponds to the bulges of the cloth.

Asexual reproduction occurs by the typical for the Desmids dichotomy. Sexual reproduction occurs by conjugation. The zygotes are spherical, ovoid or polyhedral, and stay with the empty cell halves connected.

The cell size ranges from 60 to 300 microns.

Occurrence

The genus is found only in fresh water, in oligotrophic, stagnant waters and in bogs.

Representative

Micrasterias sp

Documents

• Karl -Heinz Linne von Berg, Kerstin Hoef -Emden, Birger Marin, Micharl Melkonian: The Cosmos algae leader. The main freshwater algae under the microscope. Kosmos, Stuttgart 2004, p 124 ISBN 3-440-09719-6.