''Compsopogon caeruleus'' is a species of

red algae Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority ...

that lives in fresh water. It is the only species in the genus ''Compsopogon'' and the only representative of the family Compsopogonaceae. It is found in North America, South America, Europe, Africa, Asia, Australasia and Oceania. ''Compsopogon'' can tolerate a wide range of conditions in freshwater streams and occasionally in brackish lagoons and estuaries. It propagates by asexual spores. ''Compsopogon'' presents a

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

of simple cylindrical cells inside large covered cortical cells. In more mature and large thallus interior cells can be disintegrated, leaving only the outer cortex. The species exhibits a wide

phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology or physical form and structure, its developmental processes, its biochemical and physiological proper ...

plasticity in studies such as field observations, with the result that historically many species have been described, when current thought treats it as a single species. There are two main morphologies in ''Compsopogon'', one displaying regular cortical cells (morphology ''caeruleus''), the other having cells with extra rhizoidals (morphology ''leptoclados'').

References

Red algae genera Compsopogonophyceae {{red alga-stub