Florideophyceae is a class of exclusively multicellular red algae. They were once thought to be the only algae to bear pit connections, but these have since been found in the filamentous stage of the Bangiaceae. They were also thought only to exhibit apical growth, but there are genera known to grow by intercalary growth. Most, but not all, genera have three phases to the life cycle. In the subclass Nemaliophycidae there are three orders, Balbianiales, Batrachospermales, and Thoreales, which lives exclusively in freshwater. When alive, the Florideophyceae appear bright red or even violet. However, when placed in cold freshwater, their red pigment dissolves, causing the algae to turn green.Newbigin, Marion I. Colour in Nature: A Study in Biology. London: J. Murray, 1898. Accessed February 25, 2026. https://www.biodiversitylibrary.org/item/115149#page/75/mode/1up
Classification
There are various classification schemes; see red algae. One option is to use the following:
Subclass Hildenbrandiophycidae Hildenbrandiales
Subclass Nemaliophycidae Acrochaetiales Balbianiales Balliales Batrachospermales Colaconematales Nemaliales Palmariales Entwisleiales Thoreales
Subclass Corallinophycidae Corallinales Corallinapetrales Rhodogorgonales Sporolithales
The subclass Corallinophycidae was introduced in 2007.
Subclass Ahnfeltiophycidae Ahnfeltiales Pihiellales
Subclass Rhodymeniophycidae Bonnemaisoniales Ceramiales Gelidiales Gigartinales Gracilariales Halymeniales Nemastomatales Peyssonneliales Plocamiales Rhodymeniales Acrosymphytales Atractophorales Catenellopsidales Sebdeniales
According to molecular clock analysis, Florideophyceae diverged from other red algae about 943 (817–1,049) million years ago. It split into Hildenbrandiophycidae ca. 781 (681–879) mya, Nemaliophycidae ca. 661 (597–736) mya and Corallinophycidae ca. 579 (543–617) mya, and ca. 508 (442–580) mya the split between Ahnfeltiophycidae and Rhodymeniophycidae occurred.
References
External links Tree of Life: Florideophyceae