Hyalodiscus Ehrenberg, 1845
Holotype species: Hyalodiscus laevis Ehrenberg
Original publication and holotype designation: Ehrenberg, C.G. (1845). Neue Untersuchungen über das kleinste Leben als geologisches Moment.. Bericht über die zur Bekanntmachung geeigneten Verhandlungen der Königlich-Preussischen Akademie der Wissenschaften zu Berlin, 1845: 53-87.
Fossil: This is a genus of fossil species, or a genus with a fossil type species, or a genus the type species of which was originally described as a fossil.
Description: Cells lens-shaped, occurring singly or, more commonly, in pairs united by copulae. Plastids several, irregularly discoid. A common marine genus often attached by thick mucilage pads to seaweeds, in short filaments of up to four cells, but also found in turbulent inshore waters or lying unattached on the sediments. Valves deep, watchglass-shaped to hemispherical, sometimes with a flat area at the centre; the mantle edge is turned outwards. Arrangement of the areolae may be weakly or strongly fasciculate. Valve structure with narrow bullulae; the areolae open to the inside by round pores with rotae, but at the valve centre the areolae are closed on both the inner and outer surfaces by a plain mass of silica; the genus owes its name to this central feature. In transmission electron micrographs the areolar pattern can be seen continuing into the hyaline area; it is very variable in extent (see the three light micrographs). Rimoportulae occur in a ring around the mantle edge and also sparsely scattered over the rest of the valve. Internally the rimoportulae are simple and sessile. On the outside it is difficult to distinguish the outer openings of the rimoportulae from the areolae, though in some valves there are slightly wider openings, which almost certainly represent the rimoportulae. The copulae have not been investigated in detail but appear to be very thin, porous bands.The most recent alteration to this page was made on 2018-03-13 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Comments: The relationship of this genus to Podosira needs re-investigation. Only a few species are regularly found and the others, e.g. in VanLandingham (1971), are often single records. The cells are attached to each other by conspicuous blocks of mucilage which must be secreted from around the central hyaline area yet this is not a place where there are any obvious secretory organelles.
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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=43723
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 13 March 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 01 February 2023