Percursaria Bory de Saint-Vincent, 1823

Holotype species: Conferva percursa C.Agardh

Currently accepted name for the type species: Percursaria percursa (C.Agardh) Rosenvinge

Original publication and holotype designation: B[ory de Saint-Vincent, J.B.G.M.] (1823). Confervées. In: Dictionnaire Classique d'Histoire Naturelle. (Audouin, I. et al. Eds) Vol. 4, pp. 391-393. Paris: Rey et Gravier; Baudouin Frères.

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Description: Mature thallus filamentous and unbranched, largely biseriate, cells of filaments paired and forming two longitudinal rows. Filaments attached to substrate by monostromatic prostrate discs of coalesced branched filaments. Cells of disc mostly isodiametric or slightly elongate. Disc can give rise to several upright filaments. Upright filaments uniseriate at first, later becoming biseriate by a longitudinal division of cells behind the apical cell. Cells of filaments rectangular or slightly rounded, 10 to 25 µm wide by 10 to 40 µm long. Single parietal chloroplast with 1-4 pyrenoids. Life history an alternation of isomorphic gametophytes and sporophytes. Asexual reproduction by quadriflagellated zoospores; sexual reproduction by biflagellated anisogametes. Zoospores 4 to 5 µm wide by 7 to 8 µm long; male gametes ca. 2 µm wide by 6 to 7 um long; female gametes 3 to 4 µm wide by 6 to 7 µm long. Zoospores and gametes sometimes observed to be released from same thallus. Swarmers with stigma and phototactic. Swarmers leave fertile cells in mass while enclosed within a hyaline envelope, from which they burst moments later. Zoospores, zygotes, and gametes (apomictotic and parthenogenetic) develop into prostrate basal discs which later give rise to upright filaments, or directly into upright filaments attached by rhizoidal cells.

Information contributed by: C. Tanner & M.D. Guiry. The most recent alteration to this page was made on 2012-11-05 by M.D. Guiry.

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

Comments: Percursaria is more or less cosmopolitan in temperate waters and tropical waters, in brackish tidepools, lagoons and salt marshes. Epilithic or on other hard substrates, often entangled with floating mats of algae. Percursaria resembles most other members of the Ulvaceae in its life history, early development and cell structure, but differs by never developing beyond the biseriate filamentous stage. Release of swarmers in a hyaline envelope resembles that of Capsosiphon.

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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.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 05 November 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 25 September 2023

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