Austrolithon A.S.Harvey & Woelkerling, 1995
Holotype species: Austrolithon intumescens A.S.Harvey & Woelkerling
Original publication and holotype designation: Harvey, A.S. & Woelkerling, W.J. (1995). An account of Austrolithon intumescens gen. et. sp. nov. and Boreolithon van-heurckii (Heydrich) gen. et. comb. nov. (Austrolithoideae subfam. nov., Corallinaceae, Rhodophyta). Phycologia 34: 362-382.
Request PDFPrecise date of publication: 25 September 1995
Description: Plants calcified (but see comments), lacking genicula, composed largely of unconsolidated filaments but becoming pseudoparenchymatous in areas of conceptacle production; entirely endophytic except for portions of conceptacle roofs, growing within deformed gall-like growths of Jania rosea (the only known host ‘substrate’); haustoria unknown.
Thallus without apparent dorsiventral, radial or isobilateral organization; thallus construction diffuse to monomerous, consisting of discrete, branched filaments that become partially consolidated in areas of conceptacle production but collectively lack any regularised internal structure. Endophytic filaments apparently lacking epithallial cells but most conceptacle roof filaments each terminating in an epithallial cell; outermost walls of epithallial cells rounded or 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 that are largely but not entirely buried within deformed gall-like growths of the host. Spermatangia (male gametangia) and carpogonia (female gametangia) produced in separate conceptacles; male and female conceptacles apparently formed on different plants. Spermatangia formed on branched or more often on unbranched filaments that arise from the conceptacle chamber floor and roof; spermatangial initials at first each overlain by one or several protective cells that soon degenerate; spermatangial conceptacle roof formation occurring centripetally from groups of vegetative filaments peripheral to developing spermatangial filaments on the conceptacle chamber floor. Carpogoina terminating 2 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, conceptacles largely but not entirely buried within deformed gall-like growths of the host. Roofs of tetrasporangial conceptacles multiporate and composed of cells. Tetrasporangia each containing four zonately arranged spores and producing an apical plug that blocks a roof pore before spore release. Bisporangia unknown.
Information contributed by: Wm. J. Woelkerling. The most recent alteration to this page was made on 2010-10-05 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: Knowledge of Austrolithon and the single known species, A. intumescens, is based on the original detailed account of the type and other collections by Harvey & Woelkerling (1995) and the subsequent floristic account of Woelkerling & Harvey (1996). According to those authors, the extent to which vegetative thallus filaments are calcified is uncertain, but conceptacle roofs definitely are calcified. In terms of growth-form (Woelkerling et al. 1993), plants of Austrolithon are classed as unconsolidated.
The only known host ‘substrate’ is Jania rosea (Corallinaceae, subfamily Corallinoideae) (formerly Haliptilon roseum; see separate AlgaeBase entry). The development of gall-like deformities of infected branch tips of the host are thought (Harvey & Woelkerling 1995: 366) to be reactions triggered by the invasion of developing Austrolithon plants. Except for portions of conceptacle roofs, plants of Austrolithon develop entirely within the host. The extent to which Austrolithon intumescens may be dependent upon the host as an energy source is unknown. No haustoria or other cellular connections between host and endophyte have been found.
Biogeographically, Austrolithon presently is known only from the southern coast of Australia (South Australia, Victoria and Tasmania).
The lists below of diagnostic characters of Austrolithon, and of the higher taxa to which it belongs, are derived from data in Harvey & Woelkerling (1995), 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 Austrolithon from other genera of the Hapalidiaceae, subfamily Austrolithoideae).
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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.
Linking to this page: https://www.algaebase.org/search/genus/detail/?genus_id=42689
Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 05 October 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 18 December 2024
