Hemisphaerella Pascher, 1938

Holotype species: Hemisphaerella operculata Pascher

Original publication: Pascher, A. (1938). Heterokonten. In: Kryptogamen-Flora von Deutschland, Österreich und der Schweiz. (Rabenhorst, L. Eds) Vol. 11, Teil 3, pp. 321-480. Leipzig: Akademische Verlagsgesellschaft.

Type designated in: Pascher, A. (1939). Heterokonten. In: Kryptogamen-Flora von Deutschland, Österreich und der Schweiz. (Rabenhorst, L. Eds) Vol. 11 Teil 6, pp. 833-1092, [iii-x]. Leipzig: Akademische Verlagsgesellschaft.

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Description: Unicellular, solitary organisms attached to substratum with an enlarged base. Cells 15-22 _m diameter and 8-15 _m high, hemispherical or cap-shaped, non pedicellate with flattened, circular base encrusted with iron salts which give a brown color. The large axis of the cell is parallel to the substratum. Cell wall thick and rough comprised of two parts with the smaller apical portion often only slightly thickened. In young cells the protoplast does not occupy the entire space delimited by the cell wall, however, with age the protoplast fills the entire space. Chloroplasts two to three per cell and discoid or cup shaped and parietal, yellow green and without pyrenoids. Oil granules present. Contractile vacuoles observed in young cells. Asexual reproduction by zoospores, (two or four produced per mother cell); these ovoid, with two unequal flagella, one chloroplast, some contractile vacuoles and a stigma. Spores released by dehiscence of the upper portion of the cell which serves as a cover. Hemisphaerella always attached to filamentous algae in freshwater; known only from central Europe. Rarely reported. Genus with similar organization to Chlorothecium (Tribophyceae) from which it is distinguished based on the hemispherical shape.

Information contributed by: G. Tell. The most recent alteration to this page was made on 2021-10-05 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: Kawai, H. & Nakayama, T. (2015). Introduction (Heterokontobionta p.p.), Cryptophyta, Dinophyta, Haptophyta, Heterokontophyta (except Coscinodiscophyceae, Mediophyceae, Fragilariophyceae, Bacillariophyceae, Phaeophyceae, Eustigmatophyceae), Chlorarachniophyta, Euglenophyta. In: Syllabus of plant families. Adolf Engler's Syllabus der Pflanzenfamilien. Ed. 13. Phototrophic eukaryotic Algae. Glaucocystophyta, Cryptophyta, Dinophyta/Dinozoa, Haptophyta, Heterokontophyta/Ochrophyta, Chlorarachnniophyta/Cercozoa, Chlorophyta, Streptophyta p.p. (Frey, W. Eds), pp. 11-64, 103-139. Stuttgart: Borntraeger Science Publishers.

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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=46521

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 05 October 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 26 April 2024