Zygnematophyceae

Micrasterias in the light microscope

The jewelry algae ( Zygnemophyceae ) are a class of green algae group Charophyta. To her the two orders Desmids ( Desmidiales ) and Jochalgen include ( Zygnematales ).

Features

Common morphologic features of the two systems are the lack of any flagellated stages; Sexual reproduction occurs via conjugation, the merger unbegeißelter gametes entering passively or actively through tubes or slime cases to each other. The entire cell contents of certain cells ( Gametocysten ) converts it into a unbegeißelten gametes. All gametes are alike. The fusion of two gametes is referred to in this case as conjugation. The diploid zygote is a thick-walled Dauerzygote. Vegetative reproduction occurs by simple cell division.

The representatives are unicellular or filamentous algae, the threads are always unbranched, single row and break easily. The chloroplasts possess pyrenoids and are very diverse. In special vacuoles specific inclusions, see: tannins in Zygnematales, gypsum in some Desmidiales. The cell wall is slimy, layered and smooth ( Jochalgen ) or sculptured ( desmids )

Occurrence

The jewelry algae are freshwater residents. They live mainly on the seabed ( benthic ), rare in the open water body ( plankton).

System

The jewelry algae are approximately 4000 species the most diverse group of algae within the Charophyta. The jewelry algae as well as the order of the ornamental algae are monophyletic, while the Jochalgen form a paraphyletic group.

• Order Jochalgen ( Zygnematales )
• Order Desmids ( Desmidiales )