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Synurophyceans
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Named
after
genus Synura
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Silica-scaled
flagellates, separated from chrysophyceans
by their lack of chl.c2 and different flagellar root
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Autotrophic,
lost ability of phagotrophy
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Occurrence
predominantly oligotrophic freshwater
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Flagella
and flagellar roots are parallel (instead
of perpendicular in chrysophyceans), both held in front of cell
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Flagellar
transformation: the flagella of a given cell
are of different age; only one of the two flagella originates from the
mother cell, the other flagellum is formed after cell division by the daughter
cell
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Scales
are perforated and may carry perforated spines; produced in silica deposition
vesicles and extruded outside cell membrane; bristles are formed in separate
SDV
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Silica
depletion results in lack of scales but naked
cells continue to grow
Silicoflagellates
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External
silicon sceleton is present in at least one
life-cycle stage
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Few living
species but extensive fossile records
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Key genus:
Dictyocha
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Silica
was thought to be necessary for growth
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Kiel
Bight, Western Baltic: A new phytoplankton
bloom annual blooms discolored the water brown in May, which normally happened
to be the „clearwater phase“; nutrient balance of nitrate:silicate was
altered by eutrophication; Dictyocha speculum adapted to the new
conditions in growing without its typical silica sceleton
Pedinelids
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Characteristic
genus: Pedinella
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Unicellular
flagellates with anterior ring of microtubuli-supported
rhizopodia
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Radial
symmetry around longitudinal axis is exceptional
among algae
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Unmineralized,
organic scales on cell surface
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Plastids:
3-6 golden-brown plastids around the cell, containing chl. a,c, fucoxanthin;
heterotrophic species lack plastids
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Occurrence
predominantely marine
Trybophyceans (Xanthophyceans)
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Characteristic
genus: Tribonema; group also referred
to as Xantophytes
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Occurrence:
mostly freshwater and soil
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Cell
wall: cellulose, often H-shaped halves
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Storage
product: lipids in cytoplasmatic droplets
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Pigments:
Chl. a, c, diatoxanthin, diadinoxanthin, but fucoxanthin is lacking (appear
yellow-green)
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Appearance:
unicellular flagellates, coccoid forms, filaments, siphonaceous coenocytes
(tubular multi-nucleolate cells)
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Asexual
reproduction by nonflagellate autospores and
aplanospores or flagellated zoospores; thick-walled cysts;
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Sexual
reproduction by isogamy or oogamy; flagellate
gametes have typical ochrophyte flagella; exception: Vaucheria with
4-flagella male gametes
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