Raphidophyte

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Raphidophytes
Gonyostomum-cells.JPG
Gonyostomum semen
Scientific classification
Domain: Eukaryota
Kingdom: Chromalveolata
Phylum: Heterokontophyta
Class: Raphidophyceae
Chadefaud, 1950

Raphidophytes (formerly referred to as Chloromonadophyceae and Chloromonadineae[1]) are a small group of eukaryotic algae that includes both marine and freshwater species.[2] All raphidophytes are unicellular, with large cells (50 → 100 μm) but no cell walls. Raphidophytes possess a pair of flagella, organised such that both originate from the same invagination (or gullet). One flagellum points forwards,and is covered in hair-like mastigonemes, while the other points backwards across the cell surface, lying within a ventral groove. Raphidophytes contain numerous ellipsoid chloroplasts, which contain chlorophylls a, c1 and c2. They also make use of accessory pigments including β-carotene and diadinoxanthin. Unlike other heterokontophytes, raphidophytes do not possess the photoreceptive organelle (or eyespot) typical of this group.

In terms of ecology, raphidophytes occur as photosynthetic autotrophs across a range of aquatic systems. Freshwater species are more common in acidic waters, such as pools in bogs. Marine species often produce large blooms in summer, particularly in coastal waters. Off the Japanese coast, the resulting red tides often cause disruption to fish farms, although raphidophytes are not usually responsible for toxic blooms.

The position of this group varied in former classifications. Some protozoologists treated the chloromonads as an order within the phytoflagellates.[3] Some phycologists classified them with the Xanthophyceae and the Eustigmatophyceae in the division Xanthophyta.[4] Others considered them as related to Chrysophyceae, Dinophyceae or Cryptophyceae [5]

See also[edit]

References[edit]

  1. ^ Herbert Graffius, J. (1966). "Additions to Our Knowledge of Michigan Pyrrhophyta and Chloromonadophyta". Transactions of the American Microscopical Society 85 (2): 260–270. doi:10.2307/3224637. JSTOR 3224637.  edit
  2. ^ Hoek, C. van den, Mann, D. G. and Jahns, H. M. (1995). Algae : An introduction to phycology, Cambridge University Press, UK.
  3. ^ http://comenius.susqu.edu/biol/202/chromalveolata/heterokontae/raphidiophyta/default.htm
  4. ^ http://books.google.com.br/books?id=P7164wkiYxMC&lpg=PR1&hl=pt-BR&pg=PA281#v=onepage&q&f=false
  5. ^ http://www.amjbot.org/content/84/7/966.long