Chrysophyta

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Chrysophyta (krəsŏf´ətə), phylum (division) of unicellular marine or freshwater organisms of the kingdom Protista consisting of the diatoms (class Bacillariophyceae), the golden, or golden-brown, algae (class Chrysophyceae), and the yellow-green algae (class Xanthophyceae). In many chrysophytes the cell walls are composed of cellulose with large quantities of silica. Some have one or two flagella, which can be similar or dissimilar. A few species are ameboid forms with no cell walls. The food storage products of chrysophytes are oils or the polysaccharide laminarin. Formerly classified as plants, the chrysophytes contain the photosynthetic pigments chlorophyll a and c; all but the yellow-green algae also contain the carotenoid pigment fucoxanthin. Under some circumstances diatoms will reproduce sexually, but the usual form of reproduction is cell division. The diatoms and golden-brown algae are of great importance as components of the plankton and nanoplankton that form the foundation of the marine food chain.

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Chrysophyta (golden algae, golden-brown algae) A division of predominantly unicellular algae (sometimes alternatively regarded as protozoa, class Phytomastigophora) in which the chloroplasts contain large amounts of the pigment fucoxanthin, giving the algae their brown colour. Most are flagellated, having one flagellum of the tinsel type and a second flagellum of the whiplash type, which may be reduced to a short stub. Cysts or resting spores are formed which are often characteristically ornamented with spines, etc.; the cyst walls contain silica. Chrysophytes are found mainly in freshwater habitats that are low in calcium. Genera include Chromulina, Mallomonas, Ochromonas, and Synura.

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Chrysomonada (Chrysophyta; golden-brown algae) A large phylum of mostly freshwater algae that possess carotenoid pigments (responsible for their colour), in addition to chlorophylls. Their main storage products are oils and the polysaccharide chrysolaminarin. Most chrysophytes are unicellular, with two unequal-sized undulipodia (flagella), but some form colonies or are filamentous; one group of marine chrysophytes construct tests of silica.