Choreonema F.Schmitz, 1889
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.
Request PDFPrecise date of publication: 20 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
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 2017-01-20 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
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.
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.
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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.
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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 20 January 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 16 April 2024
