Rhodymenia, 1830, nom. cons.
Holotype species: Rhodymenia palmetta (Stackhouse) Greville
Currently accepted name for the type species: Rhodymenia pseudopalmata (J.V.Lamouroux) P.C.Silva
Original publication and holotype designation: Greville, R.K. (1830). Algae britannicae, or descriptions of the marine and other inarticulated plants of the British islands, belonging to the order Algae; with plates illustrative of the genera. pp. [i*-iii*], [i]-lxxxviii, -218, pl. 1-19. Edinburgh & London: McLachlan & Stewart; Baldwin & Cradock.
Taxonomic status: currently recognized as a distinct genus.
Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.
The orthography "Rhodymenia" has been conserved over the original "Rhodomenia". - (19 Oct 2015) - M.D. Guiry
Description: Thallus with erect or prostrate, usually stipitate fronds, arising from a basal disc or stolons, blades flattened, cartilaginous, simple or divided dichotomously, palmately or irregularly, sometimes with marginal or apical proliferations, occasionally perforate. Construction multiaxial, cortex of 2-5 layers of small pigmented axially elongated cells. Medulla compact, pseudoparencymatous, with large axially elongated almost colourless cells. Gametangial plants dioecious. Spermatangia in small subapical sori or large irregular patches scattered over blade, produced superficially from outer cortical cells. Procarpic, carpogonial branches 3- or 4-celled borne on a large multinucleate supporting cell also bearing a 2-celled auxiliary cell branch, gonimoblast developing outwards often with 2-3 lobes, almost all cells forming carposporangia. Cystocarps hemispherical, large and protruding, ostiolate, formed apically or scattered, tela arachnoidea absent. Tetrasporangia in subapical sori, scattered throughout the blade, or formed in special proliferations, formed in an intercalary position in unmodified cortex. Spores regularly cruciately arranged.
Information contributed by: M.D. Guiry. The most recent alteration to this page was made on 24 Jan 2017 by M.D. Guiry.
Comments: Culture studies of Rhodymenia pseudopalmata and R. holmesii Ardissone from Ireland and R. natalensis Kylin from South Africa (Guiry unpubl. obs.) were inconclusive. Although the plants grew rapidly at 20°C, no reproduction was observed under a range of temperature and daylength conditions. It is likely, however, that all species of Rhodymenia have a 'Polysiphonia-type' life history. Guiry (1977) described what may be vegetative reproductive structures occurring on the fronds of R. delicatula P.J.L. Dangeard from the British Isles. Chromosome numbers of n = 28 and 2n = 30-40 have been reported in R. pertusa from Japan (Yabu 1976) and n = 10 and 2n = 20 in R. pseudopalmata (Cole 1990).
Several morphological forms are apparent within the genus: species growing from discs vs stolons; erect vs prostrate species; species in which the tetrasporangia are localised in apical sori vs scattered throughout the thallus; species in which growth is monopodial vs ramisympodial (the latter were previously included in Dendrymenia). A range of sizes is also apparent within the genus: some species become reproductively mature at 15-20 mm (e.g., Rhodymenia delicatula), some at 50-100 (e.g., R. pseudopalmata, R. pacifica), and some at 120-1000 mm (e.g., R. pertusa).
Epymenia, regarded by some as a genus of about 14 species restricted to the colder seas of the Southern Hemisphere (South Africa, Tristan da Cunha, the Falkland I., Chile, Australasia and Kerguelen I.; see Sparling 1957: 348), and occurring mainly in the subtidal at depths of 2-60 m. Formerly separated from Rhodymenia on the basis of forming reproductive structures in specially formed leaflets, the genus is now considered synonymous with Rhodymenia (Womersley, 1996; Saunders et al., 1999).
Rhodymenia is thus a world-wide genus of some 54 species, mainly occurring in warmer waters from the lower intertidal to depths of about 100 m. In his revision of the genus, Dawson (1941) recognized many species on what appeared at first sight to be somewhat tenuous grounds; with experience, however, it becomes clear that many of the entities recognized by Dawson are indeed good species, but are difficult to distinguish without extensive material.
The spelling Rhodymenia, used by Montagne (1839), has been conserved against the original spelling Rhodomenia, used by Greville (1830). The name is to be cited as Rhodymenia Greville (1830).
Numbers of names and species: There are 152 species names in the database at present, as well as 56 infraspecific names. Of the species names, 71 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):
Click here to also show infraspecific names in the list below.
Guiry, M.D. (1977). Studies on marine algae of the British Isles. 10. The genus Rhodymenia. British Phycological Journal 12: 385-425, 62 figs, 2 tables.
Sparling, S.R. (1957). The structure and reproduction of some members of the Rhodymeniaceae. University of California Publications in Botany 29(3): (i-iv +) 319-396, 15 figs, 1 table, plates 48-59.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
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.
Created: 01 January 2001 by M.D. Guiry
Verified by: 24 January 2017 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=123
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 17 November 2018.