Yellow-green algae
| Yellow-green algae | ||||||||||||
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Botydium granulatum |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Xanthophyceae | ||||||||||||
| P. Allorge , emend. FE Fritsch |
The yellow-green algae (Xanthophyceae) are traditionally a taxon within the Heterokontophyta . Sometimes they are also called gold-green algae called or the golden algae found (Chrysophyta) in the broader sense.
features
They are mainly coccoidal to thread-like forms, rarely amoeboid , flagellate or capsoid. A cell wall is generally present, made of cellulose , and either whole or composed of H-shaped two-part shells. The cell wall can be impregnated with silica .
The plastid has a belt lamella. The outer membrane of the plastid is directly connected to the outer membrane of the cell nucleus via the endoplasmic reticulum . The DNA of your plastids ( plastid DNA ) is located in a ring-shaped genophore. The pigments are chlorophyll a and c are 1.2 , and the xanthophylls violaxanthin , hetero xanthine and Vaucherioxanthin .
Free swimming forms have two unevenly shaped flagella . The one facing forwards has three-part tubular hair, the one facing backwards has no hair. The kinetosome usually has four microtubular roots and one large striped root (rhizoplast).
Eye spots may be present.
In the light microscope one can confuse many yellow-green algae with representatives of the green algae due to the similar plastid coloration, but the latter always have real strength, which can be easily detected with iodine coloration.
Reproduction
Most species only reproduce vegetatively. Sexual reproduction with a haplontic life cycle is known only from the genus Vaucheria .
In Vaucheria , lateral protuberances develop on the thallus threads that develop into oogonia and spermatogonia. A single egg cell is formed in the oogonium. Many heterocontact flagellated spermatozoids arise in the spermatogonium. These swarm out and fertilize the egg cell. After fertilization, the oil-rich zygote forms a multilayered wall and goes into a state of rest (hypnozygote). After the end of the rest, it immediately performs a reduction division and germinates into a haploid thread.
Occurrence
The Xanthophyceae live mainly in fresh water, and a number of species also occur terrestrially ( soil algae ), such as representatives of the genera Botrydium or Xanthonema .
Systematics
The Xanthophyceae are classified in the classical system according to their morphology. However, this does not correspond to the natural relationships. According to the systematics of the eukaryotes by Adl et al. In 2012 the Xanthophyceae currently only consist of two groups:
The Tribonematales contain thread-like, coccoidale and capsoid forms, which sometimes become parenchymatic or polynuclear (see syncytium ). They include the genera:
- Botrydium
- Bumilleriopsis
- Characiopsis
- Chloromeson
- Heterococcus
- Ophiocytium
- Sphaerosorus
- Tribonema
- Xanthonema
The Vaucheriales contain only one genus. Siphonal threads and differentiated sexual organs are typical.
In total there are around 40 genera with around 600 species. In some cases, a distinction is made between significantly more orders that include several families and genera.
Web links
literature
- Joachim W. Kadereit, Christian Körner, Benedikt Kost, Uwe Sonnewald: Strasburger - Textbook of Plant Sciences. Springer Spectrum, 37th completely revised & updated edition, Berlin & Heidelberg 2014. ISBN 978-3-642-54434-7 (print); ISBN 978-3-642-54435-4 (eBook)
Individual evidence
- ↑ Adl, SM, Simpson, AGB, Lane, CE, Lukeš, J., Bass, D., Bowser, SS, Brown, MW, Burki, F., Dunthorn, M., Hampl, V., Heiss, A. , Hoppenrath, M., Lara, E., le Gall, L., Lynn, DH, McManus, H., Mitchell, EAD, Mozley-Stanridge, SE, Parfrey, LW, Pawlowski, J., Rueckert, S., Shadwick, L., Schoch, CL, Smirnov, A. and Spiegel, FW: The Revised Classification of Eukaryotes. Journal of Eukaryotic Microbiology , 59: 429-514, 2012, PDF Online