Crenotia A.Z.Wojtal, 2013

Holotype species: Crenotia thermalis (Rabenhorst) Wojtal

Original publication and holotype designation: Wojtal, A.Z. (2013). Species composition and distribution of diatom assemblages in spring waters from various geological formations in Southern Poland. Bibliotheca Diatomologica 59: [1]-436, 4 text-fig., 5 tables, 170 pls.

Description: LM. Cells with two large plate-like chloroplasts, one lying along each side of the girdle, extending under the valve face. The plates are connected by a central pyrenoid bridge. The cells are heterovalvar, with a raphid hypovalve and rapheless epivalve. They are solitary or form short chains. In girdle view the cells are bent about the median transapical plane, with a convex epivalve and concave hypovalve. Valves elliptical–lanceolate or linear, sometimes with gibbous centre. Apices broadly rounded, sometimes subcapitate. Axial areas of hypovalve and epivalve hyaline, lanceolate. Central area not clearly differentiated, sometimes unilaterally expanded up to the valve margin. Striae moderately radiate at the valve centre, 28–30 in 10 µm, becoming denser and more strongly radiate towards the apices, expanding onto the valve mantle.
SEM. Valve face of hypovalve flat, slightly convex in the central area, whereas the valve face of the epivalve is apically concave. Raphe is fine, with proximal ends not expanded or slightly expanded and with terminal ends curved in the same direction, extending onto the valve mantle. Transapical striae biseriate composed of alternating areolae of irregular outline, usually transapically elongated. The biseriate structure of the striae is always clearly visible from from inside the valve the valve face of the epivalve is apically concave. Raphe is fine, with proximal ends not expanded or slightly expanded and with terminal ends curved in the same direction, extending onto the valve mantle. Transapical striae biseriate composed of alternating areolae of irregular outline, usually transapically elongated. The biseriate structure of the striae is always clearly visible from from inside the valve and near the poles. In the centre the transapical striae are shorter and may be lacking on one side. Transapical striae end proximally with one areola, sometimes apically elongated. Internally the proximal raphe end is not expanded and the distal raphe ends terminate in helictoglossae on an elevated apical rib near the poles. Rapheless valves have a unilaterally bent axial area near the poles. The most distinctive feature of this genus is the internal structure of the transapical striae. They are composed of larger areolae openings, and proximally every stria terminates in a large, round, shallow depression covered by a thin layer of silica. Corroded structures show distal groove ornamentation to the outside valve. These depressions are visible from the outside as shadows (ghost alveolae). Girdle elements are without ornamentation (slits, areolae).

Origin of description: this description is from the original publication; it may have been modified slightly. The most recent alteration to this page was made on 2020-03-12 by Wendy Guiry.

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

Gender: This genus name is currently treated as feminine.

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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=52043

Citing AlgaeBase
Cite this record as:
Wendy Guiry in Guiry, M.D. & Guiry, G.M. 12 March 2020. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 25 November 2024