Hemiselmis Parke, 1949
Holotype species: Hemiselmis rufescens Parke
Original publication and holotype designation: Parke, M. (1949). Studies on marine flagellates. Journal of the Marine Biological Association of the United Kingdom 28: 255-288, 73 figs, 2 pls.
Request PDFDescription: Diminutive (4 - 9 &m long), free-swimming, biflagellate monads; generally bean-shaped with the flagella inserted into a vestibulum located between 1/3 and 1/2 the cell length from the anterior; a tubular gullet extends from the vestibulum obliquely across the cell (and slightly posteriorly) and is lined with usually two rows of ejectisomes; a single chloroplast, pyrenoid and nucleomorph are present, the chloroplast in some species possessing the biliprotein pigment Cr-phycoerythrin 555 and in others, Cr-phycocyanin 615 or 630; the periplast consists of internal and superficial plates that are generally hexagonal in shape. Reproduction is only known by simple cell division. Species of Hemiselmis apparently do not form palmelloid colonies, but remain motile even while dividing. The ultrastructure of several species is well known. The periplast of H. brunnescens has crystalline superficial plates and an unusual secondary layer composed of minute "sausage-like" fibrils. The nucleomorph is located outside the pyrenoid between the pyrenoid and the nucleus. There are usually two thylakoids traversing the pyrenoidal matrix. The flagella are covered with an imbricate layer of rosulate, fibrillar scales. Serial reconstruction has shown that there is only one mitochondrion per cell. A ubiquitous genus with species generally found in oceanic or coastal marine waters, although two species were described from fresh waters in the last century. Hemiselmis species may easily be overlooked in samples due to their small size and rapid movement, but can be recognized by the exaggerated corkscrew swimming motion caused by the low insertion point of the flagella.
Information contributed by: D.R.A. Hill. The most recent alteration to this page was made on 2022-10-25 by E.A. Molinari Novoa.
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: Clay, B.L., Kugrens P. & Lee, R.E. (1999). A revised classification of Cryptophyta. Botanical Journal of the Linnean Society 131: 131-152.
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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=44556
Citing AlgaeBase
Cite this record as:
E.A. Molinari Novoa in Guiry, M.D. & Guiry, G.M. 25 October 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 25 April 2024
