Udotea J.V.Lamouroux, 1812
Holotype species: Udotea flabellum (J.Ellis & Solander) M.Howe
Original publication and holotype designation: Lamouroux, [J.V.F.] (1812). Extrait d'un mémoire sur la classification des Polypiers coralligènes non entièrement pierreux. Nouveaux Bulletin des Sciences, par la Société Philomathique de Paris 3: 181-188.
Description: Thallus erect, to at least 30 cm. tall, composed of calcified blades which are funnel or fan-shaped, calcified stipe, and uncalcified mass of siphonous rhizoids. Stalk comprises a core or medullary region of longitudinally oriented siphons and cortex of their lateral appendages. Blades composed of dichotomously branched siphons, which in turn may bear simple to more complex lateral appendages; hence, blade morphology ranges from uncorticated to densely corticated. Growth not continuous as in Halimeda and Tydemania, although new lobes are added to fully formed blades in some species. Erect new blades sometimes develop from older holdfasts which have lost most of their erect photosynthetic portions, indicating a perennating system similar to that present in sand-growing species of Halimeda, and probably many of the Udoteaceae. Siphon walls, in taxa for which there are data, are composed principally of b-1,3 xylan, with cellulose apparently absent. Genus heteroplastic; hence chloroplasts with and without starch, and amyloplasts occur. Biomineralization involves deposition of aragonitic calcium carbonate which, in some species at least, occurs as a sheath surrounding filaments. For 5 species, amount of CaCO3 in mature thalli (dry weight) was ca. 33-47%. Asexual reproduction can occur by development of new thalli at ends of rhizoidal or rhizomatous extensions from holdfast. Data about sexual reproduction are equally sparse. The genus is known to be holocarpic, i.e. the contents of filaments are released into gametangia during their formation, with thallus dying after the event. Swollen siphons of the frond, to ca. 200 µm diameter and extending up to 3 cm. beyond the margin, have been interpreted as gametangia, and have been observed to release zooids contained within a gelatinous matrix. Groups of the siphons sometimes cohere below the tips. Subsequent stages of the reproductive cycle have yet to be observed.
Information contributed by: L. Hillis. The most recent alteration to this page was made on 2022-02-28 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Gender: This genus name is currently treated as neuter.
Comments: Udotea occurs globally in tropical to somewhat subtropical latitudes. Unlike Halimeda it extends into regions such as North Carolina, but local water temperatures at such sites generally fall in the subtropical range. It is common in many coralgal reef systems, and forms dense populations on sand plains at depth. Thalli are anchored sometimes on rock, but more commonly in sand, mud or peat. Vertical range is ca. -1 to at least -46m. As for Halimeda some species contain secondary chemicals which may be associated with herbivore deterrence.
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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.
Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=33621
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 28 February 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 28 March 2023