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The “goldens” (chryso-) or “golden growns” are photosynthetic protists containing chlorophylls a and c (c1 and c2), and β-linked storage reserve (chrysolaminarin). Protective pigments absorbing UV radiation include fucoxanthin and violaxanthin (Graham and Wilcox 2000).

The Chrysophyceae are similar to Bacillariophyceae, Eustigmatophyceae, Raphidophyceae, Silicoflagellates, Synurophyceae, Tribophyceae, and several additional smaller classes, and has been grouped with them in Division Ochrophyta, Kingdom Chromista (Cavalier-Smith 1986), or Stramenopiles (Brown and Sorhannus 2010). They are also grouped with other classes such as browns and diatoms that have in common two different types of flagella in the motile stages, into the "stramenopiles" ("straw hairs") and/or "heterokonts" (differing poles i.e. flagella). Included are both photosynthetic and heterotrophic forms.

The Synurophyceae (Anderson 1987) were separated from the Chrysophyceae based on the absence of chlorophyll c2, parallel basal body of the flagella (instead at ~90o angle), more gyres in the transitional helix of the flagella, absence of phagotrophy, and silica scale formation associated with the plastid (not in the cytoplasm).

Some authors group the classes Chrysophyceae, Dictyochophyceae (silicoflagellates), Synurophyceae and others together into Phylum Chrysophyta (Kristiansen 2002).   Further, the group name 'ochrophytes' (golden-brown or brown color) has been applied to all chlorophyll c containing organisms including the browns (Fucophyceae previously known as Phaeophyceae) used in a major textbook for the first time by Graham and Wilcox (2000).

The nutritional modes of Chrysophyceae include phototrophic (least number of Operational Taxonomic Units [OTUs]), mixotrohic (maxiumum nuber of OTUs), and heterotrophs (Bock et al. 20210. The maximum diversity among chrysophycean orders is the Ochromonadales, none of which are phototrophic but rather mixotrophic or heterotrohic (Bock et al. 2022).

 

References:

Anderson, R.A. 1987. Synurophyceae classic nov., a new class of algae. American J. Bot. 74:337-353.

Bock, C., Olefeld, J.L., Vogt, J.C. et al. 2022,  Phylogenetic and functional diversity of Chrysophyceae in inland waters. Org Divers Evol 22, 327–341

Brown, J.W., and U. Sorhannus 2010. A molecular genetic timescale for the diversification of autotrophic Stramenopiles (Ochrophyta): Substantive underestimation of putative fossil ages. PLoS One 5(9): e12759. doi:10.137/journal.pone.0012759.

Cavalier-Smith, 1986. The Kingdom Chromista: origin and systematics. In: Round, F.E., and D.J. Chapman, editors. Progress in Phycological Research. Bristol: Biopress. pp. 309-347.

Graham, L.E. and L.W. Wilcox  2000.  Algae.  Prentice Hall (640 pp + glossary and indices).

Kristiansen, Jorgen 2002. Phylum Chrysophyta (Golden Algae). In: The freshwater algal flora of the British Isles (pp. 214-244).

 

 

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