Desmidium
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| Scientific name | ||||||||||||
| Desmidium | ||||||||||||
| C. Agardh ex Ralfs |
Desmidium is a species from the green algae group of ornamental algae (Desmidiales) that occursin freshwater. It consists of only a few species.
features
The representatives form unbranched threads from a row of cells. The threads are 17 to 50 micrometers in diameter. The cells are loosely connected to one another and have a short cylindrical shape. They are somewhat constricted at the edge. They have a central nucleus , the chloroplast is also central and has a pyrenoid in each cell half . Two to five bumps can be seen from above. The cusps are slightly offset when the cells are adjacent, so that the threads are twisted in a screw-like manner. The threads are covered by a common jelly .
The asexual reproduction is effected by division of any cells within the thread. They remain connected to one another by the common jelly. However, the threads disintegrate easily. The sexual reproduction is done by the zygnematophyceae characteristic conjugation : two sexually different determined cells lie down together and form the area of the Isthmus Konjugationskanäle out. The two cell contents fuse to form a zygote , which enters a dormant state and forms a thick, often ornamented cell wall. The zygote germinates with reduction division.
Occurrence
The representatives of the genus are dependent on acidic locations: they sometimes occur quite frequently in bog pools, in gullies and ditches of Sphagnum bogs.
supporting documents
- Karl-Heinz Linne von Berg, Michael Melkonian u. a .: The Kosmos algae guide. The most important freshwater algae under the microscope. Kosmos, Stuttgart 2004, ISBN 3-440-09719-6 , p. 284.