Ulvophyceae

{{Short description|Class of green algae}} {{cs1 config|name-list-style=vanc|display-authors=6}} {{Automatic taxobox | fossil_range = {{long fossil range|1000|0}} | image = Ulvophyceae composite.jpg | image_caption = diversity of Ulvophyceae | image_alt = diversity of Ulvophyceae | display_parents = 3 | taxon = Ulvophyceae | authority = Stewart & Mattox, 1978<ref>{{cite journal | vauthors = Stewart KD, Mattox KR | title = Structural evolution in the flagellated cells of green algae and land plants | journal = Bio Systems | volume = 10 | issue = 1–2 | pages = 145–152 | date = April 1978 | pmid = 656563 | doi = 10.1016/0303-2647(78)90036-9 | bibcode = 1978BiSys..10..145S }}</ref><ref>{{cite journal | vauthors = Adl SM, Simpson AG, Farmer MA, Andersen RA, Anderson OR, Barta JR, Bowser SS, Brugerolle G, Fensome RA, Fredericq S, James TY, Karpov S, Kugrens P, Krug J, Lane CE, Lewis LA, Lodge J, Lynn DH, Mann DG, McCourt RM, Mendoza L, Moestrup O, Mozley-Standridge SE, Nerad TA, Shearer CA, Smirnov AV, Spiegel FW, Taylor MF | title = The new higher level classification of eukaryotes with emphasis on the taxonomy of protists | journal = The Journal of Eukaryotic Microbiology | volume = 52 | issue = 5 | pages = 399–451 | year = 2005 | pmid = 16248873 | doi = 10.1111/j.1550-7408.2005.00053.x | doi-access = free | url = http://doc.rero.ch/record/14409/files/PAL_E1847.pdf }}</ref> | subdivision_ranks = Orders | subdivision_ref = <ref name="Algaebase">{{cite web | url = http://www.algaebase.org/browse/taxonomy/#4357 | publisher = AlgaeBase version 4.2 World-wide electronic publication, National University of Ireland, Galway | access-date = 2025-05-22 | title = Class: Ulvophyceae taxonomy browser | vauthors = Guiry MD, Guiry GM | year = 2007 }}</ref> | subdivision = * Acrosiphoniales * Bryopsidales * Chlorocystidales * Cladophorales * Dasycladales * Ignatiales * Oltmannsiellopsidales * †Receptaculitales * Scotinosphaerales * Solotvyniales * Sykidiales * Trentepohliales * Ulotrichales * Ulvales

''incertae sedis'': *''Blastophysa'' *''Bubnoffphycos'' *''Sporocladopsis'' *''Trichophilus'' *''Zygomitus'' }}

The '''Ulvophyceae''' or '''ulvophytes''' are a class of green algae,<ref name="Algaebase" /> distinguished mainly on the basis of ultrastructural morphology, life cycle and molecular phylogenetic data.<ref name="Graham">{{cite book | vauthors = Graham LE, Graham JM, Wilcox LW | date = 2009 | title = Algae | edition = 2nd | publisher = Benjamin Cummings (Pearson) | location = San Francisco, CA }}</ref> The sea lettuce, ''Ulva'', belongs here. Other well-known members include ''Caulerpa'', ''Codium'', ''Acetabularia'', ''Cladophora'', ''Trentepohlia'' and ''Monostroma''.

The Ulvophytes are diverse in their morphology and their habitat. Most are seaweeds such as those listed above. Others, such as ''Rhizoclonium'', ''Pithophora'' and some species of ''Cladophora'' live in fresh water<ref>{{Cite book|title=Evolution of Primary Producers in the Sea| vauthors = O'Kelly CJ |publisher=Academic Press|year=2007|isbn=9780123705181|pages=297|chapter=The Origin and Early Evolution of Green Plants|doi=10.1016/B978-012370518-1/50014-X}}</ref> and in some areas are considered weeds.<ref>{{Cite web|url=https://www.lakemat.com/terms-for-weeds-your-lake-bottom-blanket-prevents/ | archive-url = https://web.archive.org/web/20200926075501/https://www.lakemat.com/terms-for-weeds-your-lake-bottom-blanket-prevents/ | archive-date = 26 September 2020 | work = Lakemat |title = Terms for Weeds Your Lake Bottom Blanket Prevents|date = 2 November 2019}}</ref>

==Morphology== Ulvophycean algae are diverse in morphology. The thalli are typically colonial (some are unicellular). A few taxa have flagella in their vegetative stage, such as ''Oltmannsiellopsis''. Common forms include filaments (both unbranched and branched), tubular and blade-like thalli (such as in ''Ulva''), and siphonous thalli. Siphonous thalli are composed of a single giant cell (siphon) with thousands of nuclei and chloroplasts.<ref name=Skaloud/>

The life cycle of members of the Ulvophyceae are similarly diverse. Species often reproduce asexually by forming aplanospores, akinetes or zoospores; zoospores have two or four flagella. Asexual reproduction may also occur through fragmentation of the thallus, where the pieces of the thallus grow into a new organism. Sexual reproduction is isogamous or anisogamous, and may be haplontic or diplohaplontic (i.e., involving an alternation of generations). In several taxa, the zygote exists as a small, microscopic dormant stage (also interpreted as a unicellular sporophyte) and is called the ''Codiolum'' phase.<ref name=Skaloud/>

=== Ultrastructure === The class Ulvophyceae was originally defined by K. R. Mattox and K. D. Stewart based on ultrastructural characters. These were: a counter-clockwise arrangement of the flagellar basal bodies, cytokinesis by furrowing, a closed persistent mitotic spindle, and the lack of a phycoplast. The cell wall composition and structure are highly variable, and in the flagellate life stages of some organisms, there is no cell wall altogether. The order Trentepohliales has a unique set of ultrastructural features (such as the presence of a phragmoplast), and was once considered to be its own separate class, the Trentepohliophyceae. Most of these ultrastructural characters are found in other lineages of algae, which has made defining Ulvophyceae difficult.<ref name=Skaloud>{{cite book | last1 = Škaloud | first1 = Pavel | last2 = Rindi | first2 = Fabio | last3 = Boedeker | first3 = Christian | last4 = Leliaert | first4 = Frederik | title = Chlorophyta: Ulvophyceae | series = Süßwasserflora von Mitteleuropa | volume = 13 | publisher = Springer Spektrum | location = Berlin, Germany | year = 2018 | isbn = 978-3-662-55494-4 | doi = 10.1007/978-3-662-55495-1 | url = https://link.springer.com/book/10.1007/978-3-662-55495-1 | pages=i-x, 1–289 }}</ref>

==Ecology== The Ulvophyceae are most diverse in marine habitats. A substantial number of species also live in brackish or freshwater habitats; in temperate regions they are typically most abundant during the spring and summer months. They may be found in still (e.g. lakes and ponds) or flowing waters (e.g. rivers and streams); they are typically attached to a substrate such as rocks, sediments, other aquatic algae, or occasionally animals like turtles or mollusc shells. Similarly, some species live in terrestrial habitats growing on soil, rocks, trees, plants, and other artificial substrates.<ref name=Skaloud/>

Ulvophycean algae are often beneficial to their habitats; for example, ''Cladophora'' has been described as an ecosystem engineer and provides a range of niches for other aquatic organisms. However, ''Cladophora'' and a few other taxa, such as ''Pithophora'' and ''Ulva'' often form nuisance blooms due to eutrophication.<ref name=Skaloud/>

Some species of ulvophytes are endosymbiotic within other algae, such as ''Ulvella'' which grows within other filamentous algae. Within the terrestrial order Trentepohliales, some taxa form symbioses with lichens as their phycobionts.<ref name=Skaloud/> Marine lichens also host some Ulvophyceae as symbionts; the diversity of these symbiotic algae is currently under-studied.<ref>{{cite journal|doi=10.1111/jpy.13234 |title=Lichens from the littoral zone host diverse Ulvophycean photobionts |date=2022 |last1=Černajová |first1=Ivana |last2=Schiefelbein |first2=Ulf |last3=Škaloud |first3=Pavel |last4=Johnson |first4=X. |journal=Journal of Phycology |volume=58 |issue=2 |pages=267–280 |pmid=35032341 |bibcode=2022JPcgy..58..267C }}</ref>

The family Trentepohliaceae is unusual in that it contains a few parasitic genera. For example, ''Cephaleuros'' is an endophyte within the leaves of vascular plants. ''Cephaleuros'' can cause significant economic damage to crop plants.<ref name=Brooks>{{cite journal|doi=10.1094/PDIS-01-15-0029-FE |title=The Trentepohliales (Ulvophyceae, Chlorophyta): An Unusual Algal Order and its Novel Plant Pathogen— ''Cephaleuros'' |date=2015 |last1=Brooks |first1=Fred |last2=Rindi |first2=Fabio |last3=Suto |first3=Yasuo |last4=Ohtani |first4=Shuji |last5=Green |first5=Mark |journal=Plant Disease |volume=99 |issue=6 |pages=740–753 |pmid=30699526 |bibcode=2015PlDis..99..740B }}</ref>

==Evolution== The origin and early diversification of the Ulvophyceae likely took place in the late Neoproterozoic,<ref name="VerbruggenAshworth2009">{{cite journal | vauthors = Verbruggen H, Ashworth M, LoDuca ST, Vlaeminck C, Cocquyt E, Sauvage T, Zechman FW, Littler DS, Littler MM, Leliaert F, De Clerck O | title = A multi-locus time-calibrated phylogeny of the siphonous green algae | journal = Molecular Phylogenetics and Evolution | volume = 50 | issue = 3 | pages = 642–653 | date = March 2009 | pmid = 19141323 | doi = 10.1016/j.ympev.2008.12.018 | bibcode = 2009MolPE..50..642V | author-link8 = Diane S. Littler }}</ref><ref name="CocquytVerbruggen2010">{{cite journal | vauthors = Cocquyt E, Verbruggen H, Leliaert F, De Clerck O | title = Evolution and cytological diversification of the green seaweeds (Ulvophyceae) | journal = Molecular Biology and Evolution | volume = 27 | issue = 9 | pages = 2052–2061 | date = September 2010 | pmid = 20368268 | doi = 10.1093/molbev/msq091 | doi-access = free }}</ref> though may have taken place earlier, in the Mesoproterozoic.<ref name=Hou>{{cite journal | vauthors = Hou Z, Ma X, Shi X, Li X, Yang L, Xiao S, De Clerck O, Leliaert F, Zhong B | title = Phylotranscriptomic insights into a Mesoproterozoic-Neoproterozoic origin and early radiation of green seaweeds (Ulvophyceae) | journal = Nature Communications | volume = 13 | issue = 1 | article-number = 1610 | date = March 2022 | pmid = 35318329 | pmc = 8941102 | doi = 10.1038/s41467-022-29282-9 | bibcode = 2022NatCo..13.1610H }}</ref> Although most contemporary ulvophytes are marine macroalgae (seaweeds), ancestral ulvophytes may have been freshwater, unicellular green algae. Molecular phylogenetic evidence suggests that macroscopic growth was achieved independently in the various major lineages of Ulvophyceae (Ulvales-Ulotrichales, Trentepohliales, Cladophorales, Bryopsidales and Dasycladales).<ref name="CocquytVerbruggen2010" />

The fossil record of Ulvophyceae is generally sparse, as most algae do not biomineralize well. Nevertheless, some orders such as the Dasycladales and Bryopsidales have calcified thalli and a more extensive fossil record. The earliest known representative is the Cladophorales ''Proterocladus antiquus'' from the Mesoproterozoic-Neoproterozoic boundary in North China. However, its taxonomic placement is not certain.<ref>{{cite journal | last1 = Tang | first1 = Qing | last2 = Pang | first2 = Ke | last3 = Yuan | first3 = Xunlai | last4 = Xiao | first4 = Shuhai | title = A one-billion-year-old multicellular chlorophyte | journal = Nature Ecology & Evolution | volume = 4 | pages = 543–549 | date = February 2020 | issue = 4 | doi = 10.1038/s41559-020-1122-9 | pmid = 32094536 | pmc = 8668152 | bibcode = 2020NatEE...4..543T }}</ref>

Because Ulvophyceae lacks a consistent set of ultrastructural characteristics, its monophyly has been questioned. Molecular phylogenetic studies have found Ulvophyceae to be monophyletic, albeit without strong support. The internal relationships between the different clades is also unclear. Current hypothesis on relationships among the main clades of Ulvophyceae are shown below:<ref name=Skaloud/><ref name="leliaert">{{cite journal | vauthors = Leliaert F, Smith DR, Moreau H, Herron MD, Verbruggen H, Delwiche CF, De Clerck O |year=2012 |title=Phylogeny and molecular evolution of the green algae |url=http://images.algaebase.org/pdf/5628E58F0ecc431F0CsJm2B04CAD/49951.pdf |doi=10.1080/07352689.2011.615705 |journal=Critical Reviews in Plant Sciences |volume=31 |pages=1–46 |bibcode=2012CRvPS..31....1L |s2cid=17603352 }}</ref><ref>{{cite journal|doi=10.3390/microorganisms12050868|doi-access=free |title=''Solotvynia'', a New Coccoid Lineage among the Ulvophyceae (Chlorophyta) |date=2024 |last1=Darienko |first1=Tatyana |last2=Pröschold |first2=Thomas |journal=Microorganisms |volume=12 |issue=5 |page=868 |pmid=38792698 |pmc=11123690 }}</ref>

{{clade |state=dashed |1= {{clade |state=dashed |state1=dashed |1={{clade |state=dashed |state1=dashed |1=Trentepohliales |state2=dashed |2={{clade |1=Cladophorales |2=''Blastophysa'' (''incertae sedis'') }} |state3=dashed |3={{clade |state=dashed |state1=dashed |1=Bryopsidales |state2=dashed |2=Dasycladales }} }} |state2=dashed |2={{clade |1={{clade |1={{clade |1={{clade |1=Ulotrichales |2=Acrosiphoniales }} |2={{clade |1=Sykidiales |2={{clade |1=Solotvyniales |2={{clade |1=Ulvales |2=Chlorocystidales }} }} }} }} |2=Oltmannsiellopsidales }} |2=Ignatiales |3=Scotinosphaerales }} }} }}

== See also == * List of Ulvophyceae genera {{clear}} == References == {{Reflist}}

{{Plant classification}} {{Taxonbar|from=Q132016}}

Category:Ulvophyceae Category:Green algae classes