red algae#Fossil record

File:Botryocladia occidentalis.jpg

Chloroplasts probably evolved following an endosymbiotic event between an ancestral, photosynthetic cyanobacterium and an early eukaryotic phagotroph.{{Cite journal|last1=Gould|first1=S.B.|last2=Waller|first2=R.F.|last3=McFadden|first3=G.I.|year=2008|title=Plastid Evolution|journal=Annual Review of Plant Biology|volume=59|pages=491–517|doi=10.1146/annurev.arplant.59.032607.092915|pmid=18315522|s2cid=30458113}} This event (termed primary endosymbiosis) is at the origin of the red and green algae (including the land plants or Embryophytes which emerged within them) and the glaucophytes, which together make up the oldest evolutionary lineages of photosynthetic eukaryotes, the Archaeplastida.{{Cite journal|last=McFadden|first=G.I.|year=2001|title=Primary and Secondary Endosymbiosis and the Evolution of Plastids|journal=Journal of Phycology|volume=37|issue=6|pages=951–959|doi=10.1046/j.1529-8817.2001.01126.x|s2cid=51945442}} A secondary endosymbiosis event involving an ancestral red alga and a heterotrophic eukaryote resulted in the evolution and diversification of several other photosynthetic lineages such as Cryptophyta, Haptophyta, Stramenopiles (or Heterokontophyta), and Alveolata. In addition to multicellular brown algae, it is estimated that more than half of all known species of microbial eukaryotes harbor red-alga-derived plastids.{{Cite web|url=https://www.the-scientist.com/steal-my-sunshine-39996|title=Steal My Sunshine|website=The Scientist Magazine®}}

Red algae are divided into the Cyanidiophyceae, a class of unicellular and thermoacidophilic extremophiles found in sulphuric hot springs and other acidic environments,{{Cite journal|last1=Ciniglia|first1=C.|last2=Yoon|first2=H.|last3=Pollio|first3=A.|last4=Bhattacharya|first4=D.|year=2004|title=Hidden biodiversity of the extremophilic Cyanidiales red algae|journal=Molecular Ecology|volume=13|issue=7|pages=1827–1838|doi=10.1111/j.1365-294X.2004.02180.x|pmid=15189206|bibcode=2004MolEc..13.1827C |s2cid=21858509}} an adaptation partly made possible by horizontal gene transfers from prokaryotes,{{Cite web|url=https://www.science.org/content/article/plants-and-animals-sometimes-take-genes-bacteria-study-algae-suggests|title=Plants and animals sometimes take genes from bacteria, study of algae suggests - Sciencemag.org}} with about 1% of their genome having this origin,{{Cite journal|title=The genomes of polyextremophilic cyanidiales contain 1% horizontally transferred genes with diverse adaptive functions|first1=Alessandro W|last1=Rossoni|first2=Dana C|last2=Price|first3=Mark|last3=Seger|first4=Dagmar|last4=Lyska|first5=Peter|last5=Lammers|first6=Debashish|last6=Bhattacharya|first7=Andreas PM|last7=Weber|editor-first1=Diethard|editor-last1=Tautz|editor-first2=Paul B|editor-last2=Rainey|editor-first3=Gregory|editor-last3=Fournier|date=May 31, 2019|journal=eLife|volume=8|pages=e45017|doi=10.7554/eLife.45017|doi-access=free |pmid=31149898 |pmc=6629376}} and two sister clades called SCRP (Stylonematophyceae, Compsopogonophyceae, Rhodellophyceae and Porphyridiophyceae) and BF (Bangiophyceae and Florideophyceae), which are found in both marine and freshwater environments. The BF are macroalgae, seaweed that usually do not grow to more than about 50 cm in length, but a few species can reach lengths of 2 m.{{cite journal| pmc=5547612 | pmid=28716924 | doi=10.1073/pnas.1703088114 | volume=114 | issue=31 | title=Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta) | year=2017 | journal=Proceedings of the National Academy of Sciences of the United States of America | pages=E6361–E6370 | last1 = Brawley | first1 = SH | bibcode=2017PNAS..114E6361B | author-link=Susan Brawley|doi-access=free }} In the SCRP clade the class Compsopogonophyceae is multicellular, with forms varying from microscopic filaments to macroalgae. Stylonematophyceae have both unicellular and small simple filamentous species, while Rhodellophyceae and Porphyridiophyceae are exclusively unicellular.[https://ia801206.us.archive.org/24/items/Algae_Anatomy_Biochemistry_and_Biotechnology_2nd_Edition_By_Laura_Barsanti_Paolo/Algae_Anatomy_Biochemistry_and_Biotechnology_2nd_Edition_By_Laura_Barsanti_Paolo_Gualtieri.pdf Algae: Anatomy, Biochemistry, and Biotechnology, Second Edition (page 27)]{{Cite journal|url=https://onlinelibrary.wiley.com/doi/10.1111/j.1529-8817.2008.00467.x|title=PHYLOGENETIC RELATIONSHIPS WITHIN THE STYLONEMATALES (STYLONEMATOPHYCEAE, RHODOPHYTA): BIOGEOGRAPHIC PATTERNS DO NOT APPLY TO STYLONEMA ALSIDII ¹|first1=Giuseppe C.|last1=Zuccarello|first2=John A.|last2=West|first3=Norio|last3=Kikuchi|date=April 11, 2008|journal=Journal of Phycology|volume=44|issue=2|pages=384–393|via=CrossRef|doi=10.1111/j.1529-8817.2008.00467.x|pmid=27041194 |bibcode=2008JPcgy..44..384Z }} Most rhodophytes are marine with a worldwide distribution, and are often found at greater depths compared to other seaweeds. While this was formerly attributed to the presence of pigments (such as phycoerythrin) that would permit red algae to inhabit greater depths than other macroalgae by chromatic adaption, recent evidence calls this into question (e.g. the discovery of green algae at great depth in the Bahamas).{{Cite journal|last1=Norris|first1=J. N.|last2=Olsen|first2=J. L.|date=1991|title=Deep-water green algae from the Bahamas, including Cladophora vandenhoekii sp. nov. (Cladophorales)|journal=Phycologia|language=en|volume=30|issue=4|pages=315–328|doi=10.2216/i0031-8884-30-4-315.1|bibcode=1991Phyco..30..315N |issn=0031-8884}} Some marine species are found on sandy shores, while most others can be found attached to rocky substrata.{{Cite book|last1=Kain|first1=J.M.|title=Biology of the Red Algae|last2=Norton|first2=T.A.|publisher=Cambridge University Press|year=1990|isbn=978-0521343015|editor-last=Cole|editor-first=J.M.|location=Cambridge, U.K.|pages=377–423|chapter=Marine Ecology|author-link=Joanna M. Kain|editor-last2=Sheath|editor-first2=R.G.}} Freshwater species account for 5% of red algal diversity, but they also have a worldwide distribution in various habitats; they generally prefer clean, high-flow streams with clear waters and rocky bottoms, but with some exceptions.{{Cite journal

|url = http://www.oandhs.org/files/60.pdf

|journal = International Journal of Oceanography and Hydrobiology

|volume = XXXIII

|issue = 1

|issn = 1730-413X

|pages = 47–54

|year = 2004

|title = Indicator value of freshwater red algae in running waters for water quality assessment

|author1 = Eloranta, P.

|author2 = Kwandrans, J.

|url-status = dead

|archive-url = https://web.archive.org/web/20110727135339/http://www.oandhs.org/files/60.pdf

|archive-date = 2011-07-27

}} A few freshwater species are found in black waters with sandy bottoms {{Cite journal|last1=Vis|first1=M.L.|last2=Sheath|first2=R.G.|last3=Chiasson|first3=W.B.|year=2008|title=A survey of Rhodophyta and associated macroalgae from coastal streams in French Guiana|journal=Cryptogamie Algologie|volume=25|pages=161–174}} and even fewer are found in more lentic waters.{{Cite book|title=Biology of the Red Algae|last1=Sheath|first1=R.G.|last2=Hambrook|first2=J.A.|publisher=Cambridge University Press|year=1990|isbn=978-0521343015|editor-last=Cole|editor-first=K.M.|location=Cambridge, U.K.|pages=423–453|chapter=Freshwater Ecology|editor-last2=Sheath|editor-first2=R.G.}} Both marine and freshwater taxa are represented by free-living macroalgal forms and smaller endo/epiphytic/zoic forms, meaning they live in or on other algae, plants, and animals. In addition, some marine species have adopted a parasitic lifestyle and may be found on closely or more distantly related red algal hosts.{{Cite journal|last=Goff|first=L.J.|year=1982|title=The biology of parasitic red algae|journal=Progress Phycological Research|volume=1|pages=289–369}}{{Cite journal|last1=Salomaki|first1=E.D.|last2=Lane|first2=C.E.|year=2014|title=Are all red algal parasites cut from the same cloth?|journal=Acta Societatis Botanicorum Poloniae|volume=83|issue=4|pages=369–375|doi=10.5586/asbp.2014.047|doi-access=free}}

{{Further|Wikispecies:Rhodophyta}}

In the classification system of Adl et al. 2005, the red algae are classified in the Archaeplastida, along with the glaucophytes and the green algae plus land plants (Viridiplantae or Chloroplastida). The authors use a hierarchical arrangement where the clade names do not signify rank; the class name Rhodophyceae is used for the red algae. No subdivisions are given; the authors say, "Traditional subgroups are artificial constructs, and no longer valid."

{{Cite journal | first = Sina M. | last = Adl | title = The New Higher Level Classification of Eukaryotes with Emphasis on the Taxonomy of Protists | journal = Journal of Eukaryotic Microbiology | year=2005 | volume=52 | issue=5 | pages=399–451 | doi = 10.1111/j.1550-7408.2005.00053.x | pmid=16248873 | s2cid = 8060916 |display-authors=etal| doi-access = free }} Many subsequent studies provided evidence that is in agreement for monophyly in the Archaeplastida (including red algae).{{cite journal|title=Phylogenomics Reshuffles the Eukaryotic Supergroups|editor1-first=Geraldine|editor1-last=Butler|author=Fabien Burki|author2=Kamran Shalchian-Tabrizi|author3=Marianne Minge|author4=Åsmund Skjæveland|author5=Sergey I. Nikolaev|author6=Kjetill S. Jakobsen|author7=Jan Pawlowski|journal=PLOS ONE|volume=2|issue=8|doi=10.1371/journal.pone.0000790|pmc=1949142|pmid=17726520|year=2007|pages=e790|bibcode=2007PLoSO...2..790B|doi-access=free}}{{Cite journal |year=2009 |first1=Fabien |last1=Burki |first2=Yuji |last2=Inagaki |first3=Jon |last3=Bråte |first4=John M. |last4=Archibald |first5=Patrick J. |last5=Keeling |first6=Thomas |last6=Cavalier-Smith |first7=Miako |last7=Sakaguchi |first8=Tetsuo |last8=Hashimoto |first9=Ales |last9=Horak |first10=Surendra |last10=Kumar |first11=Dag |last11=Klaveness |first12=Kjetill S. |last12=Jakobsen |first13=Jan |last13=Pawlowski |first14=Kamran |last14=Shalchian-Tabrizi |title=Large-Scale Phylogenomic Analyses Reveal That Two Enigmatic Protist Lineages, Telonemia and Centroheliozoa, Are Related to Photosynthetic Chromalveolates |journal=Genome Biology and Evolution |volume=1 |pages=231–8 |doi=10.1093/gbe/evp022 |pmc=2817417 |pmid=20333193}}{{Cite journal|last=Cavalier-Smith |first=Thomas |author-link=Thomas Cavalier-Smith |year=2009 |title=Kingdoms Protozoa and Chromista and the eozoan root of the eukaryotic tree |journal=Biology Letters|volume=6|issue=3 |pages=342–5 |doi=10.1098/rsbl.2009.0948|pmc=2880060 |pmid=20031978}}{{Cite journal|last1=Rogozin |first1=I.B. |last2=Basu |first2=M.K.|last3=Csürös |first3=M.|last4=Koonin|first4=E.V. |year=2009 |title=Analysis of Rare Genomic Changes Does Not Support the Unikont–Bikont Phylogeny and Suggests Cyanobacterial Symbiosis as the Point of Primary Radiation of Eukaryotes |journal=Genome Biology and Evolution|pmid=20333181 |volume=1|pmc=2817406|pages=99–113 |doi=10.1093/gbe/evp011 |name-list-style=amp }} However, other studies have suggested Archaeplastida is paraphyletic.{{Cite journal |last1=Kim |first1=E. |last2=Graham|first2=L.E. |last3=Graham |first3=Linda E. |editor1-last=Redfield |editor1-first=Rosemary Jeanne |title=EEF2 analysis challenges the monophyly of Archaeplastida and Chromalveolata |journal=PLOS ONE |volume=3 |issue=7|page=e2621 |year=2008|pmid=18612431|pmc=2440802|doi=10.1371/journal.pone.0002621 |name-list-style=amp |bibcode=2008PLoSO...3.2621K |doi-access=free }}{{Cite journal |last1=Nozaki |first1=H. |last2=Maruyama |first2=S. |last3=Matsuzaki |first3=M. |last4=Nakada |first4=T. |author5=Kato, S. |author6=Misawa, K. |year=2009 |title=Phylogenetic positions of Glaucophyta, green plants (Archaeplastida) and Haptophyta (Chromalveolata) as deduced from slowly evolving nuclear genes |journal=Molecular Phylogenetics and Evolution |volume=53 |issue=3 |pages=872–880 |doi=10.1016/j.ympev.2009.08.015 |pmid=19698794 }} {{As of|2020|January}}, the general consensus is that Archaeplastida is paraphyletic.{{Cite journal |last=Burki |first=Fabien |last2=Roger |first2=Andrew J. |last3=Brown |first3=Matthew W. |last4=Simpson |first4=Alastair G. B. |date=2020-01-01 |title=The New Tree of Eukaryotes |url=https://linkinghub.elsevier.com/retrieve/pii/S0169534719302575 |journal=Trends in Ecology & Evolution |language=English |volume=35 |issue=1 |pages=43–55 |doi=10.1016/j.tree.2019.08.008 |issn=0169-5347 |pmid=31606140}}

Below are other published taxonomies of the red algae using molecular and traditional alpha taxonomic data; however, the taxonomy of the red algae is still in a state of flux (with classification above the level of order having received little scientific attention for most of the 20th century).{{cite journal |author1=G. W. Saunders |author2=M. H. Hommersand |name-list-style=amp |year=2004 |title=Assessing red algal supraordinal diversity and taxonomy in the context of contemporary systematic data |journal=American Journal of Botany |volume=91 |pages=1494–1507 |doi=10.3732/ajb.91.10.1494 |issue=10 |pmid=21652305|s2cid=9925890 |doi-access= }}

• If the kingdom Plantae is defined as the Archaeplastida, then red algae will be part of that group.
• If Plantae are defined more narrowly, to be the Viridiplantae, then the red algae might be excluded.

A major research initiative to reconstruct the Red Algal Tree of Life (RedToL) using phylogenetic and genomic approach is funded by the National Science Foundation as part of the Assembling the Tree of Life Program.

Some sources (such as Lee) place all red algae into the class "Rhodophyceae". (Lee's organization is not a comprehensive classification, but a selection of orders considered common or important.{{rp|107}})

A subphylum - Proteorhodophytina - has been proposed to encompass the existing classes Compsopogonophyceae, Porphyridiophyceae, Rhodellophyceae and Stylonematophyceae.{{cite journal | last1 = Muñoz-Gómez | first1 = SA | last2 = Mejía-Franco | first2 = FG | last3 = Durnin | first3 = K | last4 = Colp | first4 = M | last5 = Grisdale | first5 = CJ | last6 = Archibald | first6 = JM | last7 = Ch | first7 = Slamovits | year = 2017 | title = The new red algal subphylum Proteorhodophytina comprises the largest and most divergent plastid genomes known | journal = Curr Biol | volume = 27 | issue = 11| pages = 1677–1684 | doi = 10.1016/j.cub.2017.04.054 | pmid = 28528908 | doi-access = free | bibcode = 2017CBio...27E1677M }} This proposal was made on the basis of the analysis of the plastid genomes.

{{See also|Eukaryote#Phylogeny}}

Over 7,000 species are currently described for the red algae, but the taxonomy is in constant flux with new species described each year. The vast majority of these are marine with about 200 that live only in fresh water.

Some examples of species and genera of red algae are:

• Cyanidioschyzon merolae, a primitive red alga
• Atractophora hypnoides
• Gelidiella calcicola
• Lemanea, a freshwater genus
• Palmaria palmata, dulse
• Schmitzia hiscockiana
• Chondrus crispus, Irish moss
• Mastocarpus stellatus
• Vanvoorstia bennettiana, became extinct in the early 20th century
• Acrochaetium efflorescens
• Audouinella, with freshwater as well as marine species
• Polysiphonia ceramiaeformis, banded siphon weed
• Vertebrata simulans

While Cyanidiophyceae is universally agreed to be the most basal, the remaining 6 classes in the subphylum Rhodophytina have uncertain relationships. The below cladogram follows the results of a 2016 study concerning diversification times among red algae.{{cite journal |author1=Yang, Eun |display-authors=etal |title=Divergence time estimates and the evolution of major lineages in the florideophyte red algae |journal=Scientific Reports |date=19 February 2016 |url=https://www.nature.com/articles/srep21361}}

{{clade

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|1=Cyanidiophyceae File:Cyanidium O5A.jpg

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|1={{clade

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|1=Porphyridiophyceae 70px

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|1=Compsopogonophyceae File:Erythrotrichia carnea Crouan.jpg

|2=Stylonematophyceae 70px

}}

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|1=Rhodellophyceae

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|1=Bangiophyceae File:Porphyra umbilicalis.jpg

|2=Florideophyceae File:New Zealand Mosses Am media-v-838854 (Plocamium spp.).jpg

}}

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Red algal morphology is diverse ranging from unicellular forms to complex parenchymatous and non- parenchymatous thallus.{{cite journal | last1 = Goff | first1 = L. J. | last2 = Coleman | first2 = A. W. | year = 1986 | title = A Novel Pattern of Apical Cell Polyploidy, Sequential Polyploidy Reduction and Intercellular Nuclear Transfer in the Red Alga Polysiphonia | journal = American Journal of Botany | volume = 73 | issue = 8| pages = 1109–1130 | doi=10.1002/j.1537-2197.1986.tb08558.x}} Red algae have double cell walls. The outer layers contain the polysaccharides agarose and agaropectin that can be extracted from the cell walls as agar by boiling. The internal walls are mostly cellulose. They also have the most gene-rich plastid genomes known.{{Cite journal|doi=10.1371/journal.pone.0059001|title=Evolution of Red Algal Plastid Genomes: Ancient Architectures, Introns, Horizontal Gene Transfer, and Taxonomic Utility of Plastid Markers|year=2013|last1=Janouškovec|first1=Jan|last2=Liu|first2=Shao-Lun|last3=Martone|first3=Patrick T.|last4=Carré|first4=Wilfrid|last5=Leblanc|first5=Catherine|last6=Collén|first6=Jonas|last7=Keeling|first7=Patrick J.|journal=PLOS ONE|volume=8|issue=3|pages=e59001|pmid=23536846|pmc=3607583|bibcode=2013PLoSO...859001J|doi-access=free}}

Red algae do not have flagella and centrioles during their entire life cycle. The distinguishing characters of red algal cell structure include the presence of normal spindle fibres, microtubules, un-stacked photosynthetic membranes, phycobilin pigment granules,W. J. Woelkerling (1990). "An introduction". In K. M. Cole; R. G. Sheath (eds.). Biology of the Red Algae. Cambridge University Press, Cambridge. pp. 1–6. {{ISBN|978-0-521-34301-5}}. pit connection between cells, filamentous genera, and the absence of chloroplast endoplasmic reticulum.{{cite journal | last1 = Scott | first1 = J. | last2 = Cynthia | first2 = B. | last3 = Schornstein | first3 = K. | last4 = Thomas | first4 = J. | year = 1980 | title = Ultrastructure of Cell Division and Reproductive Differentiation of Male Plants in the Florideophyceae (Rhodophyta): Cell Division in Polysiphonia1 | journal = Journal of Phycology | volume = 16 | issue = 4| pages = 507–524 | doi=10.1111/j.1529-8817.1980.tb03068.x| bibcode = 1980JPcgy..16..507S | s2cid = 83062611 }}

File:2023 Rhodophyte.svg

The presence of the water-soluble pigments called phycobilins (phycocyanobilin, phycoerythrobilin, phycourobilin and phycobiliviolin), which are localized into phycobilisomes, gives red algae their distinctive color.{{cite journal | last1 = Gantt | first1 = E | year = 1969 | title = Properties and Ultrastructure of Phycoerythrin From Porphyridium cruentum12 | journal = Plant Physiology | volume = 44 | issue = 11| pages = 1629–1638 | doi = 10.1104/pp.44.11.1629 | pmid = 16657250 | pmc = 396315 }} Their chloroplasts contain evenly spaced and ungrouped thylakoids{{Cite book |title=The Fine Structure of Algal Cells - 1st Edition |url=https://shop.elsevier.com/books/the-fine-structure-of-algal-cells/dodge/978-0-12-219150-3 |access-date=2023-08-16 |date=January 1973 |isbn=978-0-12-219150-3 |last=Dodge |first=John David |publisher=Academic Press }}

and contain the pigments chlorophyll a, α- and β-carotene, lutein and zeaxanthin. Their chloroplasts are enclosed in a double membrane, lack grana and phycobilisomes on the stromal surface of the thylakoid membrane.{{cite journal | last1 = Tsekos | first1 = I. | last2 = Reiss | first2 = H.-D. | last3 = Orfanidis | first3 = S. | last4 = Orologas | first4 = N. | year = 1996 | title = Ultrastructure and supramolecular organization of photosynthetic membranes of some marine red algae | journal = New Phytologist | volume = 133 | issue = 4| pages = 543–551 | doi=10.1111/j.1469-8137.1996.tb01923.x| doi-access = free }}

The major photosynthetic products include floridoside (major product), D‐isofloridoside, digeneaside, mannitol, sorbitol, dulcitol etc.{{cite journal | last1 = Karsten | first1 = U. | last2 = West | first2 = J. A. | last3 = Zuccarello | first3 = G. C. | last4 = Engbrodt | first4 = R. | last5 = Yokoyama | first5 = A. | last6 = Hara | first6 = Y. | last7 = Brodie | first7 = J. | year = 2003 | title = Low Molecular Weight Carbohydrates of the Bangiophycidae (Rhodophyta)1 | journal = Journal of Phycology | volume = 39 | issue = 3| pages = 584–589 | doi=10.1046/j.1529-8817.2003.02192.x| bibcode = 2003JPcgy..39..584K | s2cid = 84561417 }} Floridean starch (similar to amylopectin in land plants), a long-term storage product, is deposited freely (scattered) in the cytoplasm.{{cite journal |last=Lee |first=RE |date=1974 |title=Chloroplast structure and starch grain production as phylogenetic indicators in the lower Rhodophyceae |journal=British Phycological Journal |volume=9 |issue=3 |pages=291–295 |doi=10.1080/00071617400650351 }} The concentration of photosynthetic products are altered by the environmental conditions like change in pH, the salinity of medium, change in light intensity, nutrient limitation etc.{{Cite book |last1=Eggert |first1=Anja |url=https://doi.org/10.1007/978-90-481-3795-4_24 |title=Red Algae in the Genomic Age |last2=Karsten |first2=Ulf |date=2010 |publisher=Springer Netherlands |isbn=978-90-481-3795-4 |editor-last=Seckbach |editor-first=Joseph |series=Cellular Origin, Life in Extreme Habitats and Astrobiology |volume=13 |place=Dordrecht |pages=443–456 |language=en |chapter=Low Molecular Weight Carbohydrates in Red Algae – an Ecophysiological and Biochemical Perspective |doi=10.1007/978-90-481-3795-4_24 |access-date=2023-08-16 |editor2-last=Chapman |editor2-first=David J.}}

When the salinity of the medium increases the production of floridoside is increased in order to prevent water from leaving the algal cells.

{{main|Pit connection}}

Pit connections and pit plugs are unique and distinctive features of red algae that form during the process of cytokinesis following mitosis.{{Cite journal | vauthors = Clinton JD, Scott FM, Bowler E| date = November–December 1961 | title = A Light- and Electron-Microscopic Survey of Algal Cell Walls. I. Phaeophyta and Rhodophyta | journal = American Journal of Botany | volume = 48 | issue = 10 | pages = 925–934 | doi = 10.2307/2439535 | jstor = 2439535}} In red algae, cytokinesis is incomplete. Typically, a small pore is left in the middle of the newly formed partition. The pit connection is formed where the daughter cells remain in contact.

Shortly after the pit connection is formed, cytoplasmic continuity is blocked by the generation of a pit plug, which is deposited in the wall gap that connects the cells.

Connections between cells having a common parent cell are called primary pit connections. Because apical growth is the norm in red algae, most cells have two primary pit connections, one to each adjacent cell.

Connections that exist between cells not sharing a common parent cell are labelled secondary pit connections. These connections are formed when an unequal cell division produced a nucleated daughter cell that then fuses to an adjacent cell. Patterns of secondary pit connections can be seen in the order Ceramiales.

After a pit connection is formed, tubular membranes appear. A granular protein called the plug core then forms around the membranes. The tubular membranes eventually disappear. While some orders of red algae simply have a plug core, others have an associated membrane at each side of the protein mass, called cap membranes. The pit plug continues to exist between the cells until one of the cells dies. When this happens, the living cell produces a layer of wall material that seals off the plug.

The pit connections have been suggested to function as structural reinforcement, or as avenues for cell-to-cell communication and transport in red algae, however little data supports this hypothesis.{{cite web|url=https://depts.washington.edu/fhl/mb/Scagelia_Ricky/special.html |access-date=2016-06-30 |title=Pit Plugs |publisher=FHL Marine Botany}}

==Reproduction==

The reproductive cycle of red algae may be triggered by factors such as day length. Red algae reproduce sexually as well as asexually. Asexual reproduction can occur through the production of spores and by vegetative means (fragmentation, cell division or propagules production).In Archibald, J. M., In Simpson, A. G. B., & In Slamovits, C. H. (2017). Handbook of the protists.

Red algae lack motile sperm. Hence, they rely on water currents to transport their gametes to the female organs – although their sperm are capable of "gliding" to a carpogonium's trichogyne. Animals also help with the dispersal and fertilization of the gametes. The first species discovered to do so is the isopod Idotea balthica.{{Cite web |last=Tamisiea |first=Jack |title=In a First, Tiny Crustaceans Are Found to 'Pollinate' Seaweed like Bees of the Sea |url=https://www.scientificamerican.com/article/in-a-first-tiny-crustaceans-are-found-to-ldquo-pollinate-rdquo-seaweed-like-bees-of-the-sea/ |access-date=2023-08-16 |website=Scientific American |language=en}}

The trichogyne will continue to grow until it encounters a spermatium; once it has been fertilized, the cell wall at its base progressively thickens, separating it from the rest of the carpogonium at its base.

Upon their collision, the walls of the spermatium and carpogonium dissolve. The male nucleus divides and moves into the carpogonium; one half of the nucleus merges with the carpogonium's nucleus.

The polyamine spermine is produced, which triggers carpospore production.

Spermatangia may have long, delicate appendages, which increase their chances of "hooking up".

They display alternation of generations. In addition to a gametophyte generation, many have two sporophyte generations, the carposporophyte-producing carpospores, which germinate into a tetrasporophyte – this produces spore tetrads, which dissociate and germinate into gametophytes. The gametophyte is typically (but not always) identical to the tetrasporophyte.{{Cite journal| author = Kohlmeyer, J.| date = February 1975| title = New Clues to the Possible Origin of Ascomycetes| journal = BioScience| volume = 25| issue = 2| pages = 86–93| doi = 10.2307/1297108| jstor = 1297108}}

Carpospores may also germinate directly into thalloid gametophytes, or the carposporophytes may produce a tetraspore without going through a (free-living) tetrasporophyte phase. Tetrasporangia may be arranged in a row (zonate), in a cross (cruciate), or in a tetrad.

The carposporophyte may be enclosed within the gametophyte, which may cover it with branches to form a cystocarp.

The two following case studies may be helpful to understand some of the life histories algae may display:

In a simple case, such as Rhodochorton investiens:

:In the carposporophyte: a spermatium merges with a trichogyne (a long hair on the female sexual organ), which then divides to form carposporangia – which produce carpospores.

:Carpospores germinate into gametophytes, which produce sporophytes. Both of these are very similar; they produce monospores from monosporangia "just below a cross-wall in a filament" and their spores are "liberated through the apex of sporangial cell."

:The spores of a sporophyte produce either tetrasporophytes. Monospores produced by this phase germinates immediately, with no resting phase, to form an identical copy of the parent. Tetrasporophytes may also produce a carpospore, which germinates to form another tetrasporophyte.

:The gametophyte may replicate asexually using monospores, but also produces nonmotile sperm in spermatangia, and a lower, nucleus-containing "egg" region of the carpogonium.{{Cite book |last1 = Raven |first1 = Peter H. |last2 = Evert |first2 = Ray F. |last3 = Eichhorn |first3 = Susan E. |date = 2005 |title = Biology of Plants 7th ed. |publisher = W.H. Freeman and Company Publishers, New York |page = 324 |isbn = 0-7167-1007-2 }}

A rather different example is Porphyra gardneri:

:In its diploid phase, a carpospore can germinate to form a filamentous "conchocelis stage", which can also self-replicate using monospores. The conchocelis stage eventually produces conchosporangia. The resulting conchospore germinates to form a tiny prothallus with rhizoids, which develops to a cm-scale leafy thallus. This too can reproduce via monospores, which are produced inside the thallus itself. They can also reproduce via spermatia, produced internally, which are released to meet a prospective carpogonium in its conceptacle.

{{Algal carbon isotopes}}

The {{delta|13|C|link}} values of red algae reflect their lifestyles. The largest difference results from their photosynthetic metabolic pathway: algae that use HCO₃ as a carbon source have less negative {{delta|13|C}} values than those that only use {{co2}}. {{cite journal |last1=Maberly |first1=SC |last2=Raven |first2=JA |last3=Johnston |first3=AM |date=1992 |title=Discrimination between 12C and 13C by marine plants |journal=Oecologia |volume=91 |issue=4 |page=481 |doi=10.1007/BF00650320 }} An additional difference of about 1.71‰ separates groups intertidal from those below the lowest tide line, which are never exposed to atmospheric carbon. The latter group uses the more ¹³C-negative {{co2}} dissolved in sea water, whereas those with access to atmospheric carbon reflect the more positive signature of this reserve.

Photosynthetic pigments of Rhodophyta are chlorophylls a and d. Red algae are red due to phycoerythrin. They contain the sulfated polysaccharide carrageenan in the amorphous sections of their cell walls, although red algae from the genus Porphyra contain porphyran. They also produce a specific type of tannin called phlorotannins, but in a lower amount than brown algae do.

As enlisted in realDB,{{Cite journal |last1=Chen |first1=Fei |last2=Zhang |first2=Jiawei |last3=Chen |first3=Junhao |last4=Li |first4=Xiaojiang |last5=Dong |first5=Wei |last6=Hu |first6=Jian |last7=Lin |first7=Meigui |last8=Liu |first8=Yanhui |last9=Li |first9=Guowei |last10=Wang |first10=Zhengjia |last11=Zhang |first11=Liangsheng |date=2018-01-01 |title=realDB: a genome and transcriptome resource for the red algae (phylum Rhodophyta) |url=https://doi.org/10.1093/database/bay072 |journal=Database |language=en |volume=2018 |doi=10.1093/database/bay072 |issn=1758-0463 |pmc=6051438 |pmid=30020436}} 27 complete transcriptomes and 10 complete genomes sequences of red algae are available. Listed below are the 10 complete genomes of red algae.

• Cyanidioschyzon merolae, Cyanidiophyceae{{cite journal | last1 = Matsuzaki | display-authors = etal | title = Genome sequence of the ultrasmall unicellular red alga Cyanidioschyzon merolae 10D | journal = Nature | volume = 428 | issue = 6983| pages = 653–657 | doi = 10.1038/nature02398 | pmid=15071595 | date=April 2004| bibcode = 2004Natur.428..653M | doi-access = free }}{{cite journal | last1 = Nozaki | display-authors = etal | year = 2007 | title = A 100%-complete sequence reveals unusually simple genomic features in the hot-spring red alga Cyanidioschyzon merolae| journal = BMC Biology | volume = 5 | page = 28 |pmid=17623057 | doi = 10.1186/1741-7007-5-28|pmc=1955436 | doi-access = free }}
• Galdieria sulphuraria, Cyanidiophyceae{{cite journal | last1 = Schönknecht | display-authors = etal | title =Gene transfer from bacteria and archaea facilitated evolution of an extremophilic eukaryote | journal = Science | volume = 339 | issue = 6124| pages = 1207–1210 | doi = 10.1126/science.1231707 | pmid=23471408 | date=March 2013| bibcode = 2013Sci...339.1207S | s2cid = 5502148 | url = https://pub.uni-bielefeld.de/record/2915146 }}
• Pyropia yezoensis, Bangiophyceae{{cite journal | last1 = Nakamura | display-authors = etal| title = The first symbiont-free genome sequence of marine red alga, Susabi-nori (Pyropia yezoensis) | journal = PLOS ONE | volume = 8 | issue = 3| page = e57122 |pmid=23536760|doi = 10.1371/journal.pone.0057122|pmc=3594237| year = 2013| bibcode = 2013PLoSO...857122N| doi-access = free}}
• Chondrus crispus, Florideophyceae{{cite journal | last1 = Collen | display-authors = etal | year = 2013 | title = Genome structure and metabolic features in the red seaweed Chondrus crispus shed light on evolution of the Archaeplastida | journal = PNAS | volume = 110| issue = 13| pages = 5247–5252| doi = 10.1073/pnas.1221259110 | pmid=23503846 | pmc=3612618| bibcode = 2013PNAS..110.5247C | doi-access = free }}
• Porphyridium purpureum, Porphyridiophyceae{{cite journal | last1 = Bhattacharya | display-authors = etal | year = 2013 | title = Genome of the red alga Porphyridium purpureum | journal = Nature Communications | volume = 4 | page = 1941 | doi = 10.1038/ncomms2931 | pmid = 23770768 | pmc = 3709513 | bibcode = 2013NatCo...4.1941B }}
• Porphyra umbilicalis, Bangiophyceae{{cite journal|display-authors=4|last1=Brawley|first1=SH|author-link1=Susan Brawley|last2=Blouin|first2=NA|last3=Ficko-Blean|first3=E|last4=Wheeler|first4=GL|last5=Lohr|first5=M|last6=Goodson|first6=HV|last7=Jenkins|first7=JW|last8=Blaby-Haas|first8=CE|last9=Helliwell|first9=KE|last10=Chan|first10=CX|last11=Marriage|first11=TN|last12=Bhattacharya|first12=D|last13=Klein|first13=AS|last14=Badis|first14=Y|last15=Brodie|first15=J|last16=Cao|first16=Y|last17=Collén|first17=J|last18=Dittami|first18=SM|last19=Gachon|first19=CMM|last20=Green|first20=BR|last21=Karpowicz|first21=SJ|last22=Kim|first22=JW|last23=Kudahl|first23=UJ|last24=Lin|first24=S|last25=Michel|first25=G|last26=Mittag|first26=M|last27=Olson|first27=BJSC|last28=Pangilinan|first28=JL|last29=Peng|first29=Y|last30=Qiu|first30=H|last31=Shu|first31=S|last32=Singer|first32=JT|last33=Smith|first33=AG|last34=Sprecher|first34=BN|last35=Wagner|first35=V|last36=Wang|first36=W|last37=Wang|first37=ZY|last38=Yan|first38=J|last39=Yarish|first39=C|last40=Zäuner-Riek|first40=S|last41=Zhuang|first41=Y|last42=Zou|first42=Y|last43=Lindquist|first43=EA|last44=Grimwood|first44=J|last45=Barry|first45=KW|last46=Rokhsar|first46=DS|last47=Schmutz|first47=J|last48=Stiller|first48=JW|last49=Grossman|first49=AR|last50=Prochnik|first50=SE| title=Insights into the red algae and eukaryotic evolution from the genome of Porphyra umbilicalis (Bangiophyceae, Rhodophyta)|journal=Proceedings of the National Academy of Sciences of the United States of America|date=1 August 2017|volume=114|issue=31|pages=E6361–E6370|doi=10.1073/pnas.1703088114|pmid=28716924|pmc=5547612|bibcode=2017PNAS..114E6361B |doi-access=free}}
• Gracilaria changii, Gracilariales{{cite journal | last1 = Ho | first1 = C.-L. | last2 = Lee | first2 = W.-K. | last3 = Lim | first3 = E.-L. | year = 2018 | title = Unraveling the nuclear and chloroplast genomes of an agar producing red macroalga, Gracilaria changii (Rhodophyta, Gracilariales) | journal = Genomics | volume = 110 | issue = 2| pages = 124–133 | doi=10.1016/j.ygeno.2017.09.003| pmid = 28890206 | doi-access = free }}
• Galdieria phlegrea, Cyanidiophytina{{cite journal | last1 = Qiu | first1 = H. | last2 = Price | first2 = D. C. | last3 = Weber | first3 = A. P. M. | last4 = Reeb | first4 = V. | last5 = Yang | first5 = E. C. | last6 = Lee | first6 = J. M. | last7 = Bhattacharya | first7 = D. | year = 2013 | title = Adaptation through horizontal gene transfer in the cryptoendolithic red alga Galdieria phlegrea | journal = Current Biology | volume = 23 | issue = 19| pages = R865–R866 | doi=10.1016/j.cub.2013.08.046| pmid = 24112977 | doi-access = free | bibcode = 2013CBio...23.R865Q }}
• Gracilariopsis lemaneiformis, Gracilariales{{cite journal | last1 = Zhou | first1 = W. | last2 = Hu | first2 = Y. | last3 = Sui | first3 = Z. | last4 = Fu | first4 = F. | last5 = Wang | first5 = J. | last6 = Chang | first6 = L. | last7 = Li | first7 = B. | year = 2013 | title = Genome Survey Sequencing and Genetic Background Characterization of Gracilariopsis lemaneiformis (Rhodophyta) Based on Next-Generation Sequencing | journal = PLOS ONE | volume = 8 | issue = 7| page = e69909 | doi=10.1371/journal.pone.0069909| pmid = 23875008 | pmc = 3713064 | bibcode = 2013PLoSO...869909Z | doi-access = free }}
• Gracilariopsis chorda, GracilarialesJunMo Lee, Eun Chan Yang, Louis Graf, Ji Hyun Yang, Huan Qiu, Udi Zelzion, Cheong Xin Chan, Timothy G Stephens, Andreas P M Weber, Ga Hun Boo, Sung Min Boo, Kyeong Mi Kim, Younhee Shin, Myunghee Jung, Seung Jae Lee, Hyung-Soon Yim, Jung-Hyun Lee, Debashish Bhattacharya, Hwan Su Yoon, "Analysis of the Draft Genome of the Red Seaweed Gracilariopsis chorda Provides Insights into Genome Size Evolution" in Rhodophyta, Molecular Biology and Evolution, Volume 35, Issue 8, August 2018, pp. 1869–1886, {{doi|10.1093/molbev/msy081}}

==Fossil record==

One of the oldest fossils identified as a red alga is also the oldest fossil eukaryote that belongs to a specific modern taxon. Bangiomorpha pubescens, a multicellular fossil from arctic Canada, strongly resembles the modern red alga Bangia and occurs in rocks dating to 1.05 billion years ago.

Two kinds of fossils resembling red algae were found sometime between 2006 and 2011 in well-preserved sedimentary rocks in Chitrakoot, central India. The presumed red algae lie embedded in fossil mats of cyanobacteria, called stromatolites, in 1.6 billion-year-old Indian phosphorite – making them the oldest plant-like fossils ever found by about 400 million years.{{cite journal|last1=Bengtson|first1=S|last2=Sallstedt|first2=T|last3=Belivanova|first3=V|last4=Whitehouse|first4=M|date=2017|title=Three-dimensional preservation of cellular and subcellular structures suggests 1.6 billion-year-old crown-group red algae|journal=PLOS Biol|volume=15|issue=3|doi=10.1371/journal.pbio.2000735|page=e2000735|pmid=28291791|pmc=5349422|doi-access=free}}

Red algae are important builders of limestone reefs. The earliest such coralline algae, the solenopores, are known from the Cambrian period. Other algae of different origins filled a similar role in the late Paleozoic, and in more recent reefs.

Calcite crusts that have been interpreted as the remains of coralline red algae, date to the Ediacaran Period.{{Cite journal

|author1=Grant, S. W. F. |author2=Knoll, A. H. |author3=Germs, G. J. B. | year = 1991

| title = Probable Calcified Metaphytes in the Latest Proterozoic Nama Group, Namibia: Origin, Diagenesis, and Implications

| journal = Journal of Paleontology

| volume = 65

| issue = 1

| pages = 1–18

| pmid = 11538648

| jstor=1305691

|doi=10.1017/S002233600002014X |bibcode=1991JPal...65....1G |s2cid=26792772 }} Thallophytes resembling coralline red algae are known from the late Proterozoic Doushantuo formation.{{Cite journal

|author1=Yun, Z. |author2=Xun-lal, Y. | year = 1992

| title = New data on multicellular thallophytes and fragments of cellular tissues from Late Proterozoic phosphate rocks, South China

| journal = Lethaia

| volume = 25

| issue = 1

| pages = 1–18

| doi = 10.1111/j.1502-3931.1992.tb01788.x

|bibcode=1992Letha..25....1Y }}

Chromista and Alveolata algae (e.g., chrysophytes, diatoms, phaeophytes, dinophytes) seem to have evolved from bikonts that have acquired red algae as endosymbionts. According to this theory, over time these endosymbiont red algae have evolved to become chloroplasts. This part of endosymbiotic theory is supported by various structural and genetic similarities.Summarised in {{cite journal|last1=Cavalier-Smith|first1=Thomas|title=Membrane heredity and early chloroplast evolution|journal=Trends in Plant Science|volume=5|issue=4|pages=174–182|doi=10.1016/S1360-1385(00)01598-3|pmid=10740299|date=April 2000}}

Red algae have a long history of use as a source of nutritional, functional food ingredients and pharmaceutical substances.Wang, T., Jónsdóttir, R., Kristinsson, H. G., Hreggvidsson, G. O., Jónsson, J. Ó., Thorkelsson, G., & Ólafsdóttir, G. (2010). "Enzyme-enhanced extraction of antioxidant ingredients from red algae Palmaria palmata". LWT – Food Science and Technology, 43(9), 1387–1393. {{doi|10.1016/j.lwt.2010.05.010}} They are a source of antioxidants including polyphenols, and phycobiliproteins and contain proteins, minerals, trace elements, vitamins and essential fatty acids.{{cite journal | last1 = MacArtain | first1 = P. | last2 = Gill | first2 = C. I. R. | last3 = Brooks | first3 = M. | last4 = Campbell | first4 = R. | last5 = Rowland | first5 = I. R. | year = 2007 | title = Nutritional Value of Edible Seaweeds | journal = Nutrition Reviews | volume = 65 | issue = 12| pages = 535–543 | doi=10.1111/j.1753-4887.2007.tb00278.x| pmid = 18236692 | s2cid = 494897 | doi-access = free }}{{Cite journal|last=Becker|first=E.W.|date=March 2007|title=Micro-algae as a source of protein|url=https://linkinghub.elsevier.com/retrieve/pii/S073497500600139X|journal=Biotechnology Advances|language=en|volume=25|issue=2|pages=207–210|doi=10.1016/j.biotechadv.2006.11.002|pmid=17196357}}

Traditionally, red algae are eaten raw, in salads, soups, meal and condiments. Several species are food crops, in particular dulse (Palmaria palmata){{cite web |url=http://www.seaveg.co.uk/dulse.html |publisher=Quality Sea Veg |title=Dulse: Palmaria palmata |access-date=2007-06-28 |archive-date=2012-02-22 |archive-url=https://web.archive.org/web/20120222192457/http://www.seaveg.co.uk/dulse.html |url-status=dead }} and members of the genus Porphyra, variously known as nori (Japan), gim (Korea), {{transliteration|zh|zicai}} {{lang|zh|紫菜}} (China), and laver (British Isles).{{cite book |author1=T. F. Mumford |author2=A. Muira |name-list-style=amp |chapter=Porphyra as food: cultivation and economics |title=Algae and Human Affairs |editor=C. A. Lembi |editor2=J. Waaland |year=1988 |publisher=Cambridge University Press, Cambridge |isbn=978-0-521-32115-0}}

Red algal species such as Gracilaria and Laurencia are rich in polyunsaturated fatty acids (eicopentaenoic acid, docohexaenoic acid, arachidonic acid)Gressler, V., Yokoya, N. S., Fujii, M. T., Colepicolo, P., Filho, J. M., Torres, R. P., & Pinto, E. (2010). "Lipid, fatty acid, protein, amino acid and ash contents in four Brazilian red algae species". Food Chemistry, 120(2), 585–590. {{doi|10.1016/j.foodchem.2009.10.028}} and have protein content up to 47% of total biomass. Where a big portion of world population is getting insufficient daily iodine intake, a 150 ug/day requirement of iodine is obtained from a single gram of red algae.Hoek, C. van den, Mann, D.G. and Jahns, H.M. (1995). Algae An Introduction to Phycology. Cambridge University Press, Cambridge. {{ISBN|0521304199}}

Red algae, like Gracilaria, Gelidium, Euchema, Porphyra, Acanthophora, and Palmaria are primarily known for their industrial use for phycocolloids (agar, algin, furcellaran and carrageenan) as thickening agent, textiles, food, anticoagulants, water-binding agents, etc.Dhargalkar VK, Verlecar XN. "Southern Ocean Seaweeds: a resource for exploration in food and drugs". Aquaculture 2009; 287: 229–242. Dulse (Palmaria palmata) is one of the most consumed red algae and is a source of iodine, protein, magnesium and calcium.{{Cite web |date=December 2013 |title=On the human consumption of the red seaweed dulse (Palmaria palmata (L.) Weber & Mohr) |url=https://www.researchgate.net/publication/257577425 |website=researchgate.net}} Red algae's nutritional value is used for the dietary supplement of algas calcareas.{{Cite journal |last1=Marone |first1=Palma Ann |last2=Yasmin |first2=Taharat |last3=Gupta |first3=Ramesh C. |last4=Bagchi |first4=Manashi |date=July 2010 |title=Safety and toxicological evaluation of AlgaeCal ® (AC), a novel plant-based calcium supplement |url=http://www.tandfonline.com/doi/full/10.3109/15376516.2010.490966 |journal=Toxicology Mechanisms and Methods |language=en |volume=20 |issue=6 |pages=334–344 |doi=10.3109/15376516.2010.490966 |pmid=20528255 |issn=1537-6516}}

China, Japan, Republic of Korea are the top producers of seaweeds.Manivannan, K., Thirumaran, G., Karthikai, D.G., Anantharaman. P., Balasubramanian, P. (2009). "Proximate Composition of Different Group of Seaweeds from Vedalai Coastal Waters (Gulf of Mannar): Southeast Coast of India". Middle-East J. Scientific Res., 4: 72–77. In East and Southeast Asia, agar is most commonly produced from Gelidium amansii. These rhodophytes are easily grown and, for example, nori cultivation in Japan goes back more than three centuries.{{Cite web |title=Nori / Gim / Kim |url=https://www.clovegarden.com/ingred/al_noriz.html |access-date=2024-12-23 |website=www.clovegarden.com}}

Researchers in Australia discovered that limu kohu (Asparagopsis taxiformis) can reduce methane emissions in cattle. In one Hawaii experiment, the reduction reached 77%. The World Bank predicted the industry could be worth ~$1.1 billion by 2030. As of 2024, preparation included three stages of cultivation and drying. Australia's first commercial harvest was in 2022. Agriculture accounts for 37% of the world’s anthropogenic methane emissions. One cow produces between 154 and 264 pounds of methane/yr.{{Cite web |last=Heaton |first=Thomas |date=2024-06-03 |title=Cattle Are A Major Source Of Greenhouse Gas Emissions. Hawaii Seaweed Could Change That |url=https://www.civilbeat.org/2024/06/hawaii-seaweed-could-dramatically-improve-the-environmental-impact-of-cattle-farming/ |access-date=2024-06-04 |website=Honolulu Civil Beat |language=en}}

Other algae-based markets include construction materials, fertilizers and other agricultural inputs, bioplastics, biofuels and fabric. Red algae also provides ecosystem services such as filtering water and carbon sequestration.

• Brown algae
• Green algae
• History of phycology
• Litostroma (1959)

{{Clear}}

{{Reflist|30em|refs=

{{Fritsch 1945}}

}}

• [http://www.algaebase.org/browse/taxonomy/?id=97240 AlgaeBase: Rhodophyta]
• [http://www.seaweed.ie/algae/rhodophyta.html Seaweed Site: Rhodophyta] {{Webarchive|url=https://web.archive.org/web/20120709091258/http://www.seaweed.ie/algae/rhodophyta.html |date=2012-07-09 }}
• [http://tolweb.org/Rhodophyta/2381 Tree of Life: Rhodophyta] {{Webarchive|url=https://web.archive.org/web/20120502185037/http://tolweb.org/Rhodophyta/2381 |date=2012-05-02 }}
• [https://web.archive.org/web/20070206081344/http://www.mbari.org/staff/conn/botany/flora/reds.htm Monterey Bay Flora]

{{Life on Earth}}

{{Eukaryota|D.}}

{{Plant classification}}

{{Taxonbar|from=Q103169}}

{{Authority control}}

Category:Proterozoic first appearances