Stictocyclus A.Mann, 1925

Holotype species: Stictocyclus varicus A.Mann

Currently accepted name for the type species: Stictocyclus stictodiscus (Grunow) R.Ross

Original publication and holotype designation: Mann, A. (1925). Marine diatoms of the Philippine Islands. Bulletin United States National Museum 100(6, part 1): 1-182, 39 pls.

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Description: Cells cylindrical, lying with the multiple copulae visible; attached loosely by the edges of the valve faces to form filaments. Plastids discoid, lobed. recorded from tropical regioins, but only rarely' epiphytic. The one known species has sometimes been put in Actinocyclus or Ethmodiscus, but was confirmed in Stictocyclus (as S. stictodiscus) by Ross & Sims (1973). Valves petri-dish like, with prominent radial ribs, which become indistinct towards the centre. The ribs become thicker and buttress-like at the angle between valve face and mantle and thin out in the centre and along the valve mantle. Valve face flat, sharply differentiated from the deep, vertical mantles. Note: Fig. a has a central segment of the sibling valve lying on the complete valve. Areolae arranged in radial rows, several occurring between each pair of ribs. Towards the centre, where the ribs disappear, the areolae are replaced with scattered puncta, which in SEM are seen to be elongate openings of the rimoportulae. A large pseudonodulus occurs on one side and is closed by a fine plate sunken below a slight rim. Areolae somewhat irregular in outline, with small inwardly projecting pegs supporting a velum. The rimoportulae are short and curved internally and open by elongate slits externally; they are scattered over the central area and also extend slightly amongst the rows of areolae, where they penetrate the siliceous framework rather than replacing the areolae. Copulae complete, numerous, areolate as in the valves, with long fimbriae on their advalvar edges.

The most recent alteration to this page was made on 2015-12-07 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Nikolaev, V.A., Kociolek, J.P., Fourtanier, E., Barron, J.A. & Harwood, D.M. (2001). Late Cretaceous diatoms (Bacillariophyceae) from the Marca Shale member of the Moreno Formation, California. Occasional Papers of the California Academy of Sciences 152: 1-119, 39 plates.

Comments: This genus was studied by Ricard (1970) and Ricard & Gasse (1972), from material collected in Tahiti, and its basic structure described. Round (1978) reported on the SEM structure of material collected in Hawaii and discussed its classification, placing it in a new family, the Stictocyclaceae. Its relationship to other families is still not clear since the presence of a pseudonodulus removes it from the Coscinodiscales and points to a position near the Eupodiscales. However, this order does not possess central rimoportulae and has valves that tend to be loculate (see Round, 1978a, for further discussion).

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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.

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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 07 December 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 05 December 2024

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