Pterosperma Pochet, 1893: 178, footnote
Lectotype species: Pterosperma rotondum Pouchet
Taxonomic status: currently recognized as a distinct genus.
Description: Unicellular green algae occurring in two phases. The coccoid stage, the Phycoma, measures 14-230 _m in diameter when mature. It is surrounded by a double wall, the inner wall delicate and containing pectic material, the outer wall tough and of unknown composition, perhaps containing material related to sporopollenin. Outer wall smooth, hebetate, papillose and/or poroid, bearing one or more alae (wings) protruding at right angles from the wall surface. The alae divide the surface into two halves or into triangular, quadrangular or polygonal areas. Mature Phycoma contain a single nucleus at first, and numerous chloroplasts each with a pyrenoid. Cell divisions take place in the mature Phycoma, resulting in the formation of a large number of quadriflagellate swarmers. These are released through a slit in the outer wall, still surrounded by the inner wall. Eventually the inner wall bursts, liberating the swarmers. Swarmers with 4 very long flagella (3-10 times cell diameter) which in the swimming cell are directed backwards and held together as a "compound flagellum" (Inouye and others 1990). They contain a single chloroplast with pyrenoid, but lack eyespot. Extrusomes are located beneath the plasmalemma. All surfaces covered with organic scales of several kinds. Cell body with three-layered scale covering, the inner layer consisting of tiny square scales, the outer layers of 2-3 types of roughly octagonal or nonagonal plates. Flagella covered with square/rounded underlayer scales, overlaid by limuloid scales. Two opposite rows of hair-shaped scales are also present. Fission in the motile stage. Sexual reproduction unknown. The changeover from Phycoma to motile phase is apparently related to lunar periodicity. The species differ mainly in the morphology of the Phycoma, notably the structure of the outer wall, including the arrangement of the alae. The Phycoma of Pterosperma occur in all seas, but are rarely reported in large numbers. They contain substantial amounts of lipid and, being lighter than water, rise to the surface of the sea under calm conditions. Pterosperma is closely related to Pachysphaera, apparently differing only in the structure of the Phycoma. The ultrastructure of P. cristatum was studied by Hori and others (1990).
NCBI Nucleotide Sequences
Numbers of names and species: There are 21 species (and infraspecific) names in the database at present, of which 19 have been flagged as currently accepted taxonomically.
Names: ('C' indicates a name that is currently 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):
Pterosperma citriforme Parke C
Pterosperma cristatum Schiller C
Pterosperma cuboides Gaarder C
Pterosperma dictyon (Jørgensen) Ostenfeld C
Pterosperma eurypteron Parke C
Pterosperma hemisphaericum Meunier C
Pterosperma inornatum Parke C
Pterosperma joergensenii Schiller C
Pterosperma jorgensenii J.Schiller C
Pterosperma labyrinthus Ostenfeld S
Pterosperma marginatum Gaarder C
Pterosperma michaelsarsii (Gaarder) Parke & Boalch P
Pterosperma moebii (Jørgensen) Ostenfeld C
Pterosperma nationalis Lohmann C
Pterosperma ornatum J.Schiller P
Pterosperma parallelum Gaardner C
Pterosperma polygonum Ostenfeld C
Pterosperma porosum Parke C
Pterosperma rotondum Pouchet C - type
Pterosperma undulatum Ostenfeld C
Pterosperma vanhoeffenii (Jørgensen) Ostenfeld C
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: http://www.algaebase.org/search/genus/detail/?genus_id=44988
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 22 May 2013.
Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:6109