Melosira C.Agardh, 1824, nom. cons.

Holotype species: Melosira nummuloides C.Agardh

Original publication and holotype designation: Agardh, C.A. (1824). Systema algarum. pp. [i]-xxxvii, [1]-312. Lundae [Lund]: Literis Berlingianis [Berling].

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Description: Cells cylindrical to subsperical, united in filaments by mucilage pads secreted onto their valve faces; in addition irregular spines may assist the linkage. Cells united distinctively into pairs or triplets by their cingula. Plastids lobed, small plate-like, lying in the peripheral cytoplasm. A common genus in freshwater (M. varians) and marine epibenthic habitats (M. nummuloides, M. moniliformis). Valve face flat or domed, covered with small spines or granules; a more or less well-developed corona consisting of larger irregular spines is sometimes developed. This may be surrounded by a carina (a flat collar-like structure) as in M. nummuloides. Valve mantle not readily distinguishable from valve face in most species. Valve mantle edge having a milled appearance. The valve structure is loculate, the loculus being open to the outside via a number of small simple pores and to the inner surface by somewhat larger pores, which may be partially or completely bridged by silica struts (in the latter instnace forming rotae). The pattern of these inner pores is independent of the loculi (cf. Stephanopyxiz). The loculi may be randomly arranged or lie in rows radiating from the centre of the valve. Rimoportulae occur usually in a ring near the mantle edge and sometimes scattered or grouped on the valve; there is a circular external aperture surrounded by an irregular rim. The internal apertures are in the form of elongate slits also surrounded by an irregular, low rim. Copulae split, ligulate, with regular longitudinal rows of small pores; pars media distinct and near advalvar edge. The two valves are closely associated during the greater part of the cell cycle and the cingula of adjacent daughter cells overlap one another considerably.

The most recent alteration to this page was made on 2015-10-19 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Stoermer, E.F. & Julius, M.L. (2003). Centric Diatoms. In: Freshwater Algae of North America. (Wehr, J.D. & Sheath, R.G. Eds), pp. 559-594. San Diego: Academic Press.

Comments: The genus as conceived by previous workers has included a great range of taxa, some of which have been transferred to other genera (see Aulacoseira, Paralia, Orthoseira and Ellerbeckia). For reference on Melosira and related genera see Crawford, 1988.

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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=43727

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 19 October 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 17 August 2022

 
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