Hydrosera Wallich, 1858

Lectotype species: Hydrosera triquetra Wallich

Original publication: Wallich, G.C. (1858). On Triceratium and some allied forms, with figures of the same. Quarterly Journal of Microscopical Science 6: 242-253, pls Xii, XIII.

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Type designated in: Sournia, A. (1987). Atlas du phytoplancton marin. Volume II. Diatomophycées. Vol. 2 pp. 1-215. Paris: Éditions du Centre National de la Recherche Scientifique 15, quai Anatole France - 75700 Paris.

Description: Cells triangular and undulate in valve view, rectangular in girdle view; forming short chains by mucilage pads secreted at all three valve angles; attached to the substratum by secretion at one angle. Plastids: numerous, elliptical platelets (Li & Chiang, 1977). A marine epiphytic genus usually found in estuarine situations; it may penetrate upstream in rivers and even into other freshwater sites (Li & Chiang, 1977). Generally regarded as tropical but now recorded in the R. Thames, U.K. A small distinctive genus with two commonly reported species. Valves triangular, their sides undulate. Valve face flat, curving into a fairly deep mantle; both valve face and mantle coarsely areolate, the areolae being somewhat smaller on the mantle. Pseudocelli on each corner, sometimes with small blunt spines around the outer rim; similar projections may occur on other parts of the valve. Areolae loculate, with foramina externally and small round pores internally, the inner pores forming rows radiating from the valve centre. Small domed structures on the outer valve face in the pits between the outer ornamentation. No vela have been detected; nor did Li & Chiang find any though further investigation is necessary. Valve mantle edge plain. The valve has one conspicuous stalked rimoportula, with an S-shaped slit internally. Plain ridges or folds (pseudosepta) extend across the bases of the three corners of the triangular valve. Between the valve mantle and the rimoportula, which is located opposite one of the central undulations of the wall, is a region with three cavities and a short ridge (the cavities were termed pseudonoduli by Li & Chiang, 1977). The opening of the rimoportula and any connection with the bases of the cavities are not obvious from the outside. Copulae closed, finely porous, with a fimbriate edge on the valvocopula; four(?) per cell. Li & Chiang report a complex overlapping of the valvocopula onto the pseudosepta.

The most recent alteration to this page was made on 2018-05-08 by M.D. Guiry.

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

Gender: This genus name is currently treated as feminine.

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: The 'psedonoduli' do not appear comparable to those in Actinocyclus. The internal folding of the valve, loculate structure and small domed external openings in the primary layer of the wall are reminiscent of other Biddulphiaceae though the relationships of the genera are unclear. Further details are given in Qi (1984) and Qi et al. (1984).

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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=43684

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 08 May 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 18 April 2024

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