Exilicrusta Y.M.Chamberlain, 1992
Holotype species: Exilicrusta parva Y.M.Chamberlain
Original publication and holotype designation: Chamberlain, Y.M. (1992). Observations on two melobesioid crustose coralline red algal species from the British Isles - Exilicrusta parva, a new genus and species, and Lithothamnion sonderi Hauck. British Phycological Journal 27: 185-201.
Request PDFPrecise date of publication: 1 June 1992 (stated at top of first page of original publication). The requirements for valid publication are specified in the ICBN (International Code of Botanical Nomenclature).
Description: Plants calcified, lacking genicula, entirely pseudoparenchymatous; encrusting in growth-form; epigenous and growing completely attached to rock (the only known substrate); haustoria unknown. Thallus organization wholly dorsiventral; thallus construction dimerous throughout, composed of two groups of filaments: a ventral-most unistratose layer of filaments (primigenous filaments) from which marginal growth occurs; and upright filaments (postigenous filaments) 1 or more cells long that arise perpendicularly from cells of ventral filaments and lead to increase in thallus thickness. Upright filaments each normally terminating at the thallus surface in an epithallial cell; outermost epithallial cell walls flattened with flared corners; cell elongation tending to occur mainly in subepithallial initials that are usually as long as or longer than their inward derivatives. Cells of adjacent filaments linked by fusions; secondary pit-connections unknown. Gametangia and carposporangia developing in uniporate conceptacles. Spermatangia (male gametangia) and carpogonia (female gametangia) produced in separate conceptacles that usually form adjacent to one another on the same plant. Spermatangia terminal on unbranched filaments that arise from the conceptacle chamber floor but not the roof; spermatangial initials not observed; mode of spermatangial conceptacle roof formation uncertain. Carpogonia terminating 3-celled unbranched filaments arising from the conceptacle chamber floor. Carposporophytes developing in carpogonial conceptacles after presumed fertilization, each composed of a central fusion cell and several-celled filaments that arise peripherally and bear terminal carposporangia. Tetrasporangia formed in conceptacles on separate plants from gametangia and carposporangia. 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 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: Knowledge of Exilicrusta and the single known species, E. parva, is based on the original detailed account of the type and other collections by Chamberlain (1992) and the subsequent floristic treatment in Chamberlain & Irvine (1994: 162-165), who describe the species as small, obscure, difficult to find, and known from only a few specimens. In terms of growth-form (Woelkerling et al. 1993), plants of Exilicrusta are classed as encrusting. The extent to which the gametangial characters mentioned by Chamberlain (1992: 200, Table 1) are diagnostic of Exilicrusta requires further study because of the apparent rarity of Exilicrusta, and because for many species of Lithothamnion and Melobesia, spermatangia, carpogonial branches, and/or carposporophytes are unknown or poorly known. These characters have not been included in the list below.
Biogeographically, Exilicrusta presently is known only from several collections gathered on the south coast of England.
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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=42769
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 22 November 2024
