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Raphidophytes
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Small
group of few, mainly marine genera
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Appearance:
30-80 µm, long anterior flagellumwith perpendicular tripartite hairs,
smoothflagellum motionlessdirected backwards; nakedcells without scales
or cell cover
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Trichocysts
can be ejected and produce longmucilaginous strands
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Mucocysts
can produce extracellular mucilage
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Metabloy
is documented for some species
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Pigments:
Chlorophyll a and c, but some species lack chl.c; marinespecies possess
fucoxanthin and violaxanthin, whereas freshwaterforms possess diadinoxanthin
and others
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Pyrenoids
in marine but not freshwater sp.
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Phototrophic,
phagotrophy and
sexualreproduction
not observed
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Fish
kills are cause by blooms of Heterosigma
and Olisthodiscus (marine)
Chrysophytes (Chrysophyceans)
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Name:
gr. Chrysos = gold; „golden algae“;
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Color
golden brown by their predominant accessory pigment fucoxanthin
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Appearance:
unicellular flagellates or flagellated colonies, sometimes non-motile unicells,
colonies, or amoeboid stages that produce flagellated spores
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Habitat:
mostly freshwater, but also marine species; prefer slightly acidid water
(pH<7), probably because they posses an acidic but no alkaline phosphatase
(enzyme to degrade organic phosphates); abundant in the periphyton (communities
living on macroalgae)
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Stomatocysts
are heavily silicified resting stages resulting from sexual or asexual
reproduction; fossil records of chrysophycean stomatocysts and their distinct
surface structure (electron microscope) are used for geological studies;
only 10% of stomatocysts have been connected to vegetative taxa
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Nutrition
in Chrysophytes
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Nutrition:
most species mixotroph, among them chlorophyll-containing
species that act primarily as heterotrophs and use photosynthesis only
in times of scarce food supply
Dependence of Ochromonas growth
on bacteria abundance
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Important
grazers on bacteria and picoalgal communities
in freshwater and marine systems
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Freshwater
blooms of chrysophyceans can cause fish kills
by toxins or gill clogging
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Water
odor can arise from excretion of ketons and
aldehydes by chrysophyceans
The „Other“ Chrysophyte:
Hydrurus
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