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.
Taxonomic status: currently recognized as a distinct genus.
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.
Description: 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 26 May 2017 by M.D. Guiry.
Numbers of names and species: There are 16 species names in the database at present, of which 14 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..
Names: ('C' indicates a name that is accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):
Click here to also show infraspecific names in the list below.
Bérard-Therriault, L., Poulin, M. & Bossé, L. (1999). Guide d'identification du phytoplancton marin de l'estuaire et du Golfe du Saint-Laurent incluant également certains protozoaires. Publication Spéciale Canadienne des Sciences Halieutiques et Aquatiques 128: 1-387.
Hoef-Emden, K. (2008). Molecular phylogeny of phycocyanin-containing cryptophytes: evolution of biliproteins and geographical distribution. Journal of Phycology 44: 985-993.
Verification of data
Users are responsible for verifying the accuracy of information before use, as noted on the website Content page.
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.
Created: 19 August 2004 by M.D. Guiry
Verified by: 13 March 2017 by M.D. Guiry
Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=44556
Please cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 14 November 2018.