Arcocellulus Hasle, Stosch & Syvertsen, 1983

Holotype species: Arcocellulus mammifer Hasle, Stosch & Syvertsen

Original publication and holotype designation: Hasle, G.R., Stosch, H.A. von & Syvertsen, E.E. (1983). Cymatosiraceae, a new diatom family. Bacillaria 6: 9-156.

Description: Cells rectangular, genuflex or falcate in girdle view, spindle-shaped in valve view but tending towards being round in small cells. One plastid per cell. Cells solitary or chain-forming, planktonic or benthic, marine. Valves elongate to oval, sometimes with slightly capitate ends. Frustules heterovalvar, the concave valve bearing two long pili (spines) at least in larger cells. Pili attached near the poles and with reflexed branches arising from their proximal portion and short spines on the distal portion; small areas of papillae can also occur, usually towards the bases of the pili. The valve surface may be ornamented with low costae. Poroids more-or-less circular. A row of poroids lies along each margin and occasional single poroids are scattered on the valve face. The vela are fine porous membranes or cribra. A shallow marginal ridge is present which is better developed towards the apices; it is formed by a series of loops of silica. A rimoportule occurs near the centre of the convex valve. Valve mantle narrow and plain. Copulae 10-15, split and alternate, with their ends in line with the valve poles. The copulae lack pores but have more-or-less regularly arranged pits in the surface.

The most recent alteration to this page was made on 2016-05-20 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Round, F.E., Crawford, R.M. & Mann, D.G. (1990). The diatoms biology and morphology of the genera. pp. [i-ix], 1-747. Cambridge: Cambridge University Press.

Comments: The genus contains two species, which differ from each other in the attitude of pili, the curvature of the frustule in girdle view, relative valve length, velum structure, and valve markings. It is closely related to Leyanella, which has pili on the convex valves and a more elaborate marginal ridge. Arcocellulus has been thoroughly described by Hasle et al. (1983). The tubular process is presusmably a very much simplified rimoportula, and this simplification is also carried through to the ocelluli. The reduction of the valve face to a network of costae is also reminiscent of the reduction seen in some species of the quite unrelated genus Cylindrotheca (but living under similar ecological conditions).

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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.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 20 May 2016. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 26 September 2023

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