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( Red alga)
(There were formerly thought to be two classes, Florideophyceae and Bangiophyceae.)[2] The red algae (Rhodophyta, IPA /?ro?d?'fa?t?, ro?'d?f?t?/, from Greek ??d?? (rhodon) = rose + f?t?? (phyton) = plant, thus red plant) are one of the oldest groups of eukaryotic algae,[2] and also one of the largest, with about 5,000–6,000 species&_160;[3] of mostly multicellular, marine algae, including many notable seaweeds. Other references indicate 10,000 species.&_160;[4] The red algae form a distinct group characterized by the following attributes eukaryotic cells without flagella and centrioles, using floridean starch as food reserve, with phycobiliproteins as accessory pigments (giving them their red color), and with chloroplasts lacking external endoplasmic reticulum and containing unstacked thylakoids.&_160;[4] Most red algae are also multicellular, macroscopic, marine, and have sexual reproduction. Many of the coralline algae, which secrete calcium carbonate and play a major role in building coral reefs, belong here. Red algae such as dulse (Palmaria palmata) and laver (nori/gim) are a traditional part of European and Asian cuisine and are used to make other products like agar, carrageenans and other food additives.&_160;[5]
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