Pyramimonas Schmarda, 1849

Holotype species: Pyramimonas tetrarhynchus Schmarda

Original publication and holotype designation: Schmarda, L.K. (1850). Neue Formenvon Infusorien. Denkschriften der Kaiserlichen Akademie der Wissenschaften, Wien. Mathematisch-Naturwissenschaftliche Klasse 1(2): 9-14.

Description: Unicellular flagellates. Cells usually more or less inversely pyramidal, in transverse section square to rounded. Four thick flagella emerge from an anterior depression. A few species possess 8 flagella, one newly found species has 16 flagella. The cell contains a single cup-shaped chloroplast divided anteriorly into 4 or 8 lobes. It possesses a single pyrenoid posteriorly. Depending on the species, one or two eyespots are present anteriorly, in the cell middle, or posteriorly. The 16-flagellated species differs in having two chloroplasts, 2 pyrenoids and 4 eyespots. Freshwater species contain contractile vacuoles near the flagellar pit. The single nucleus is located in a lateral position near the anterior end. A few marine species form trichocysts. The flagella are notably thick and directed anteriorly, the distal part sometimes curved back along the cell. Opposite flagella form pairs which beat synchronously in opposite direction. Flagella and cell body covered with unmineralized scales in several layers. The flagella, all of equal length, are covered with an underlayer of square to diamond-shaped scales in 24 longitudinal rows, overlaid by 9 rows of limuloid scales. Two rows of hair-like scales emanate from opposite sides of each flagellum. The cell body is covered with an underlayer of square scales (in some species this layer is confined to the flagellar pit) and one or 2 layers of larger scales, the structure of which is an important species characteristic. In some species a special type of very small scales is present among the larger body scales. All scales are manufactured in the cisternae of the Golgi apparatus. Most or all are transported from the Golgi apparatus to a special container, the scale reservoir, and released to the flagellar pit through a canal from the scale reservoir. Palmelloid stages known. Sexual reproduction has not been demonstrated with certainty, but cysts are well known, sometimes with smooth, in other species with warty, spiny or scrobiculate surface. Important specific characters are cell size and (to some extent) shape, location of eyespot and pyrenoid and structure of the scaly covering. While many species have been described from fresh water, only one, the type species, is well known. It is a benthic epiphytic species which may attach by the front end to filamentous algae or other objects. Many species originally described as belonging to Pyramimonas have recently been found to lack scales, and have been transferred to the new genus Hafniomonas (Volvocales). The identity of all other remaining freshwater species remains uncertain. The marine species are mainly planktonic, while a few are benthic. Most are widely distributed (cosmopolitan), but a few species are presently known only from the Antarctic and a few from the Arctic. A large number of papers have been published on the ultrastructure of Pyramimonas since the first paper by Manton and others (1963). For general and taxonomic papers, see Inouye and others (1985), McFadden and others (1986) and Moestrup and Hill (1991). For detailed studies on the flagellar apparatus, see Melkonian (1981), Moestrup and Hori (1989) and Hori and Moestrup (1987), the latter two describing an octoflagellate species. For studies of the only known 16-flagellate species, see Daugbjerg and Moestrup (1992). For studies on scale morphogenesis, see Moestrup and Thomsen (1974) and Moestrup and Walne (1979). For flagellar movement pattern, see Inouye and Hori (1991).

Information contributed by: Ø. Moestrup. The most recent alteration to this page was made on 2014-09-22 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Moestrup, Ø. (2002). Phylum Prasinophyta. In: The Freshwater Algal Flora of the British Isles. An identification guide to freshwater and terrestrial algae. (John, D.M., Whitton, B.A. & Brook, A.J. Eds), pp. 281-286. Cambridge: Cambridge University Press.

Comments: Throndsen (1997: 655) records this as being a member of the Phylum Chromophyta.

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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.

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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 22 September 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 27 May 2024

 
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