Pterosperma Pouchet, 1893
Original publication: Pouchet, G. (1893). Histoire naturelle. In: Voyage de "La Manche" à l'Ile Jan Mayen et au Spitzberg (juillet-aôut 1892). Nouvelles Archives des Missions Scientifiques et Littéraires 5(10): 155-217.
Type designated in: Bourrelly, P. (1957). Recherches sur les Chrysophycées. Morphologie, phylogénie, systématique. Mémoire Hors-Série Revue Algologique 1: -412, incl. 11 pls.
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.
Information contributed by: Ø. Moestrup. The most recent alteration to this page was made on 2023-09-11 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 neuter.
Most recent taxonomic treatment adopted: Parke, M., Boalch, G.T., Jowett, R. & Harbour, D.S. (1978). The genus Pterosperma (Prasinophyceae): species with a single equatorial ala.. Journal of the Marine Biological Association of the United Kingdom 58: 239-276, 2 figs, 1 table, 14 pls [I-XIV].
Comments: 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).
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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=44988
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 11 September 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 06 December 2023