Red Algae


Red algae are a phylum of about 7100 mostly marine, unicellular and multicellular photosynthetic eukaryotes that belong to the Supergroup Plantae. Multicellular taxa consist exclusively of a filamentous construction lacking true tissues despite their often superficially complex plant body. This group is unique in the Tree of Life in lacking both flagella and centrioles with a 9 + 2 microtubule arrangement in all stages of the life history.

They include species with elaborate life cycles, significant ecological importance and extensive economical applications. The oldest known taxonomically resolved eukaryotic fossil, ca. 1250–1100 million years ago, is a red alga.

Key Concepts

  • Red algae are crucial organisms for understanding the evolution of sex and life cycles.
  • Red algae are crucial organisms to understand the evolution of multicellularity since the oldest eukaryote on record is a red alga.
  • Red algae are important in the evolution of photosynthetic eukaryotes since their ancestor hosted a cyanobacterium that became the plastid through the event of primary endosymbiosis.
  • Mitochondrial genomes among multicellular red algae are highly conserved, supporting the notion of a rapid radiation among the morphologically divergent multicellular lineages.
  • The calcifying coralline red algae are widespread, long‐lived barometers of ocean health and real‐time indicators of global warming and ocean acidification impacts.

Keywords: algae; endosymbiosis; biomineralisation; coralline algae; eukaryotes; fossils; life cycle; phycocolloids; rhodoliths; Rhodophyta

Figure 1. A sampling of red algal body plans: large and small unbranched blades (Halymenia); grape‐like branched thalli (Botryocladia); crustose, non‐geniculate coralline species collected in the vicinity of the Dry Tortugas, FL, at ∼50 m depth.
Figure 2. Amphiroa hancockii, a geniculate, segmented coralline, Bocas del Toro, Caribbean Panama, collected at 1 m depth.
Figure 3. Rhodolith nodules in rhodolith bed, Gulf of Chiriquí, Pacific Panama, collected at ∼20 m depth.
Figure 4. Post‐fertilisation cystocarps (carposporophytes) growing on Gracilaria intermedia female gametophytes.


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Further Reading

Baghel RS, Trivedi N, Vishal G, et al. (2015) Biorefining of marine macroalgal biomass for production of biofuel and commodity chemicals. Green Chemistry 17: 2436–2443.

Buchholz CM, Krause G and Buck BH (2012) Seaweed and man. In: Wiencke C and Bischof K (eds) Seaweed Biology, pp. 471–493. chap. 22. Berlin: Springer‐Verlag.

Charrier B, Rolland E, Gupta V and Reddy CRK (2015) Production of genetically and developmentally modified seaweeds: exploiting the potential of artificial selection techniques. Frontiers in Plant Science 6: 127. DOI: 10.3389/fpls.2015.00127.

Cole KM and Sheath RG (1990) The Biology of Red Algae, 517 pp. Cambridge, MA: Cambridge University Press.

Graham LE, Graham JM, Wilcox LW and Cook ME (2016) Algae, 3rd edn. LJLM Press. ISBN 978-0-9863935-3-2.

Lee RE (2008) Phycology, 4th edn. Cambridge University Press. ISBN 9780521682770.

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Seckbach J and Chapman D (eds) (2010) Red Algae in the Genomic Age: Volume 13 of Cellular Origin, Life in Extreme Habitats and Astrobiology. Dordrecht: Springer, ISBN 9048137942.

Sutherland JE, Lindstrom SC, Nelson WA, et al. (2011) A new look at an ancient order: generic revision of the Bangiales (Rhodophyta). Journal of Phycology 47: 1131–1151.

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Fredericq, Suzanne, and Schmidt, William E(Sep 2016) Red Algae. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0000335.pub2]