Platichthys Lange-Bertalot, Kulikovskiy, Witkowski, Seddon & Kociolek, 2015

Holotype species: Platichthys krammeri Lange-Bertalot & Kulikovskiy

Original publication and holotype designation: Lange-Bertalot, H. Witkowski, A. & Krammer, K., Kulikovskiy, M.S., Seddon, A.W.R. & Kociolek, J.P. (2015). Taxonomy, frustular morphology and systematics of Platichthys, a new genus of canal raphe bearing diatoms within the Entomoneidaceae. Phytotaxa 236(2): 135-149, 62 figs.

Description: Cells solitary. Plastids currently unknown. Frustules lying exclusively in girdle view, linear-elliptical to linear with broadly rounded ends. Between both valves the girdle consists of several barely recognizable copulae. Prominent fibulae, approximately developed as circular structures are apically arranged at some distance below the frustule margins. In straight view the fibulae lie on the same level in both valves. Consequently a nitzschioid or hantzschioid symmetry classification (i.e. raphe on the same or opposite sides, respectively) becomes obsolete. Valve ends appear slightly rostrate in an appropriately oblique position. Transapical striae, areolae, raphe canals or raphe slit are not discernible, sometimes phase contrast optics allows observation of the central nodule and the apical raphe endings. EM, valve exterior: the shape of the frustules resembles a flat tongue when the valves are separated from each other, or a cigar when the valves are connected through the girdle bands. The girdle is composed of numerous open, porous copulae. The valve face is steep and compressed laterally to form a narrow keel. Below the keel, around the mid-width, the valve becomes broader. The valve mantle is developed as a very narrow, structureless rim. The raphe runs within a well-separated, structureless axial area with two raphe branches separated by a narrow central nodule. External central raphe endings are relatively simple, slightly expanded, whereas the apical external endings are bent in the same direction. In a hypothetical cross-section of a frustule, the position of both valves is roughly like two hairpins lying opposed with the open ends connected, and the raphe canals are situated at the closed ends. Transapical striae uniseriate, very densely spaced, far beyond the resolution power of LM. The areolae are simple, sometimes, slightly transapically elongate pores. SEM, valve interior: internally the fibulae are column-shaped, short and arched. They separate the raphe canal from the major part of the valve lumen (cavity). The fibulae are positioned at some distance from the raphe. As the fibulae are large, usually a few striae merge into one fibula. Wave crests begin at the basis of fibulae while wave troughs continue into the interfibula spaces (portulae). The portulae are very simple and are formed as a result of a slight broadening of the base of the fibulae. Internally, the raphe slit is straight, the two raphe branches are separated by a narrow central nodule, whereas at the apices they terminate in a small helictoglossa. Internally, the areolae are positioned in shallow depressions formed by the virgae.

Information contributed by: Original description; slightly modified by M.D. Guiry. The most recent alteration to this page was made on 2017-10-06 by M.D. Guiry.

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

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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=51908

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 06 October 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 29 April 2024