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Choreonema F.Schmitz, 1889

Classification:
Empire Eukaryota
Kingdom Plantae
Subkingdom Biliphyta
Phylum Rhodophyta
Subphylum Eurhodophytina
Class Florideophyceae
Subclass Corallinophycidae
Order Hapalidiales
Family Hapalidiaceae
Subfamily Choreonematoideae
Tribe Choreonemateae

Holotype species: Choreonema thuretii (Bornet) F.Schmitz

Original publication and holotype designation: Schmitz, F. (1889). Systematische Übersicht der bisher bekannten Gattungen der Florideen. Flora oder Allgemeine botanische Zeitung 72: 435-456, pl. XXI.
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Precise date of publication20 Dec 1889 (publication date of journal issue; see Index Nominum Genericorum (ING) database at http://botany.si.edu./ing); the date 8 Dec 1889 is printed at the bottom of the last page of the article. The requirements for valid publicat

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.

Nomenclatural notes
New name for Endosiphonia Ardissone, 1883, nom. illeg. - (1 Dec 2012) - M.D. Guiry

Monotypic when introduced. - (20 Jan 2017) - M.D. Guiry

Description: Plants partially calcified, lacking genicula, composed of endophytic, unconsolidated filaments and pseudoparenchymatous patches that produce conceptacles external to the host; growing largely within intergenicula of branches of species of Jania (see comments); vegetative filaments possessing specialized lenticular cells that produce fimbriate processes (observable only with transmission electron microscopy) that become connected to host cells; haustoria unknown.  

Thallus without apparent dorsiventral, radial or isobilateral organization; thallus construction largely diffuse, consisting of short, discrete, unbranched or branched filaments that become partially consolidated in areas of conceptacle production but collectively lack any regularised internal structure. Lenticular cells confined to cells of endophytic filaments; epithallial cells absent from endophytic filaments but present on conceptacles; outermost walls of epithallial cells more or less flattened but not flared at the corners; cell-elongation characteristics uncertain; cells of adjacent filaments apparently not linked by cell fusions or by secondary pit-connections.

Gametangia and carposporangia developing in uniporate conceptacles. Spermatangia (male gametangia) and carpogonia (female gametangia) produced in separate conceptacles; male and female conceptacles apparently formed on different plants. Spermatangia formed on unbranched filaments that arise from the conceptacle chamber floor and roof; spermatangial initials apparently not overlain with protective cells during early stages of development; spermatangial conceptacle roof formation presumed to occur centripetally from vegetative filaments peripheral to developing spermatangial filaments on the conceptacle chamber floor. Carpogonia terminating 2-3 celled unbranched filaments that arise from the conceptacle chamber floor. Carposporophytes developing in carpogonial conceptacles after presumed fertilization; mature carposporophytes composed of a central fusion cell and several-celled filaments bearing terminal carposporangia.

Tetrasporangia formed in conceptacles on separate plants from gametangia and carposporangia. Tetrasporangial conceptacles containing an acellular multiporate plate composed only of a calcium carbonate matrix and recessed below a single outer opening bordered by laterally coherent epithallial cells; conceptacle walls composed of a single outer layer of coherent epithallial cells underlain by a layer of calcified acellular material and 1-3 layers of uncalcified or lightly calcified cells from which the epithallial cells arise. Tetrasporangia each containing four zonately arranged spores and producing an apical plug that protrudes through the overlying acellular multiporate plate and becomes tightly clustered with other plugs to collectively block the single outer conceptacle roof opening prior to spore release. Bisporangia unknown.

Information contributed by: Wm. J. Woelkerling. The most recent alteration to this page was made on 20 Jan 2017 by M.D. Guiry.

Characters considered diagnostic of Choreonema: Choreonema is the only currently recognized genus in the subfamily Choreonematoideae. The list below of diagnostic characters the Choreonematoideae, and of the higher taxa to which it belongs, are derived from data in Harvey, Broadwater, Woelkerling & Mitrovski (2003), Harvey, Woelkerling & Millar (2003), Le Gall & Saunders (2007), Woelkerling et al. (2008: 282) and/or Le Gall et al. (2009). Diagnostic characters are those that taken together distinguish a taxon from others of the same taxonomic rank (e.g. characters distinguishing the Choreonematoideae from other subfamilies of the Hapalidiaceae).

Characters considered diagnostic of higher taxonomic ranks known/presumed to occur in all species of Choreonema: 1) calcification in the form of calcite; 2) pit plugs with two cap layers at cytoplasmic faces, the outer cap dome shaped; membrane absent; 3) cell walls impregnated with calcite; 4) gametangia and carposporangia produced within uniporate conceptacles; 5) tetrasporangia/bisporangia produced within conceptacles and possessing zonately arranged spores; 6) tetrasporangial/bisporangial conceptacles possessing multiporate plates or roofs; 7) tetrasporangia/bisporangia producing apical plugs; 8) tetrasporangial/bisporangial conceptacles with roofs composed of an acellular multiporate plate recessed below a single outer opening; and 9) cells of contiguous vegetative filaments not linked by cell fusions or by secondary pit-connections. Characters 1-2 are considered diagnostic of the Corallinophycidae, 3-5 of the Corallinales, 6-7 of the Hapalidiaceae, and 8-9 of the Choreonematoideae.

Two features of Choreonema discovered from transmission electron microscope studies (the occurrence of lenticular cells with fimbriate processes connected to host cells; conceptacle walls composed of a single outer layer of coherent epithallial cells underlain by a layer of calcified acellular material and 1-3 layers of uncalcified or lightly calcified cells from which the epithallial cells arise) are unknown in other genera or subfamilies assigned to the Hapalidiaceae (or in other families assigned to the Corallinales), but to date, these characters have not been used in a formal diagnostic sense at subfamily or family levels.

Generic synonyms: Chaetolithon (Foslie 1897: 7) is regarded as a heterotypic synonym of Choreonema. Endosiphonia Ardissone (1883: 450) is an older validly published name for Choreonema but is not available because it is a later illegitimate homonym of Endosiphonia Zanardini (1878), a genus of Rhodomelaceae (Rhodophyta). See AlgaeBase entries for Chaetolithon & Endosiphonia Ardissone for further data.

Comments: Information on the taxonomic history, nomenclature, and other matters associated with the name Choreonema is contained in Woelkerling (1988: 88-92); an additional note is provided in Silva et al. (1996: 230). In terms of growth-form (Woelkerling et al. 1993), plants of Choreonema are classed as unconsolidated.

An account of the lectotype specimen of C. thuretii, the type species of Choreonema,is presented in Woelkerling (1987), who also provided an account of the species based on light microscopy and summarized references to earlier studies. The subsequent studies of Broadwater & La Pointe (1997) and Broadwater et al. (2002), based on transmission and scanning electron microscopy, significantly expanded our knowledge of the genus with discoveries that: 1) lenticular cells produce fimbriate processes that become connected to host cells, thus providing evidence for a parasitic mode of nutrition; 2) tetrasporangial conceptacles contain an acellular multiporate plate composed of a calcium carbonate matrix and recessed below a single outer opening; and 3) conceptacle walls are composed of a single outer layer of coherent epithallial cells underlain by a layer of calcified acellular material and 1-3 layers of uncalcified or lightly calcified cells from which the epithallial cells arise. These discoveries, together with molecular and other evidence presented by Harvey, Broadwater, Woelkerling & Mitrovski (2003), resulted in the placement of Choreonema and the Choreonematoideae in the family Hapalidiaceae.

Choreonema grows largely endophytically in various species of Jania (Corallinaceae, subfamily Corallinoideae), including species formerly referred to Haliptilon and Cheilosporum. Based on molecular and morphological evidence, Kim et al. (2007) concluded that Haliptilon and Cheilosporum are heterotypic synonyms of Jania.

Biogeographically, Choreonema is recorded from localities in Europe, Asia, Africa, North and South America, Indonesia, Australia, New Zealand and various islands in the Pacific and Atlantic oceans.

Numbers of names and species: There are 2 species names in the database at present, of which 1 has 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.

References
Ardissone, F. (1883). Phycologia mediterranea. Parte prima, Floridee. Memorie della Società Crittogamologica Italiana 1: i-x, 1-516.

Broadwater, S.T., Harvey, A.S., Lapoint, E.A. & Woelkerling, W.J. (2002). Conceptacle structure of the parasitic coralline red alga Choreonema thuretii (Corallinales) and its taxonmic implications. Journal of Phycology 38: 1157-1168.

Broadwater, S.T. & LaPointe, E.A. (1997). Parasitic interactions and vegetative ultrastructure of Choreonema thuretii (Corallinales, Rhodophyta). Journal of Phycology 33: 396-407, 27 figs.

Foslie, M. (1898). List of species of the Lithothamnia. Kongelige Norske Videnskabers Selskabs Skrifter 1898(3): 1-11.

Harvey, A.S., Broadwater, S.T., Woelkerling, W.J. & Mitrovski, P.J. (2003). Choreonema (Corallinales, Rhodophyta): 18S rDNA phylogeny and resurrection of the Hapalidiaceae for the subfamilies Choreonematoideae, Austrolithoideae and Melobesioideae. Journal of Phycology 39: 988-998.

Harvey, A.S., Woelkerling, W. J. & Millar, A.J.K. (2003). An account of the Hapalidiaceae (Corallinales, Rhodophyta) in south-eastern Australia. Australian Systematic Botany 16: 647-698.

Harvey, A.S., Woelkerling, W.J. & Millar, A.J.K. (2009). The genus Amphiroa (Lithophylloideae, Corallinaceae, Rhodophyta) from the temperate coasts of the Australian continent, including the newly described A. klochkovana. Phycologia 48: 258-290.

Kim, J.H., Guiry, M.D., Oak, J.H., Choi, D.-S., Kang, S.-H., Chung, H. & Choi, H.-G. (2007). Phylogenetic relationships within the tribe Janieae (Corallinales, Rhodophyta) based on molecular and morphological data: a reappraisal of Jania. Journal of Phycology 43: 1310-1319.

Le Gall, L., Payri, C.E., Bittner, C.E., & Saunders, G.W. (2010). Multigene polygenetic analyses support recognition of the Sporolithales, ord. nov. Molecular Phylogenetics and Evolution 54(1): 302-305.

Le Gall, L. & Saunders, G.W. (2007). A nuclear phylogeny of the Florideophyceae (Rhodophyta) inferred from combined EF2, small subunit and large subunit ribosomal DNA: establishing the new red algal subclass Corallinophycidae. Molecular Phylogenetics and Evolution 43: 1118-1130.

McNeill, J., Barrie, F.R., Burdet, H.M., Demouline, V., Hawksworth, D.L., Marhold, K., Nicolson, D.H., Prado, J., Silva, P.C., Skog, J.E., Wiersema, J.H. & Turland, N.J. (2006). International Code of Botanical Nomenclature (Vienna Code) adopted by the Seventeenth International Botancial Congress Vienna, Austria, July 2005. pp. [i-iv], v-xviii + 1-568. Liechtenstein: A.R.G. Gantner Verlag.

Schmitz, F. (1889). Systematische Übersicht der bisher bekannten Gattungen der Florideen. Flora oder Allgemeine botanische Zeitung 72: 435-456, pl. XXI.

Silva, P.C., Basson, P.W. & Moe, R.L. (1996). Catalogue of the benthic marine algae of the Indian Ocean. University of California Publications in Botany 79: 1-1259.

Thuret, G. & Bornet, É. (1878). Études phycologiques. Analyses d'algues marines. Publiées par les soins de M. le Dr Édouard Bornet. Ouvrage accompagné de cinquante planches gravées d'après les desssins de M. Alfred Riocreux. pp. [i-v], i-iii, 1-105, pls I-LI . Paris: G. Masson.

Woelkerling, W.J. (1986). The genus Choreonema in southern Australia and its subfamilial classification within the Corallinaceae (Rhodophyta). Phycologia 26: 111-127.

Woelkerling, W.J. (1988). The Coralline Red Algae: an analysis of the genera and subfamilies of nongeniculate Corallinaceae. pp. i-xi, 1-268, 259 figs, tables numbered by chapter. London & Oxford: British Museum (Natural History) & Oxford University Press.

Woelkerling, W.J., Millar, A.J.K., Harvey, A. & Baba, M. (2008). Recognition of Pachyarthron and Bossiella as distinct genera in the Corallinaceae, subfamily Corallinoideae (Corallinales, Rhodophyta). Phycologia 47: 265-293.

Zanardini, G. (1878). Phyceae papuanae novae vel minus cognitae a cl. O. Beccari in itinere ad Novam Guineam annis 1872-75 collectae. Nuovo Giornale Botanico Italiano 10: 34-40.

Wynne, M.J. & Schneider, C.W. (2010). Addendum to the synoptic review of red algal genera. Botanica Marina 53: 291-299.

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Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.

Contributors
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: 28 December 2000 by M.D. Guiry

Verified by: 20 January 2017 by M.D. Guiry

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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 13 November 2018.

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