Phaeosaccion Farlow, 1882

Holotype species: Phaeosaccion collinsii Farlow

Original publication and holotype designation: Farlow, W. G. (1882). Notes on New England algae. Bulletin of the Torrey Botanical Club 9: 65-68.

Description: Thallus tubular to saccate, monostromatic, up to 20 cm long and 2 cm wide, olive-brown in color, resembling young plants of Scytosiphon. Thallus somewhat constricted at the base and enlarged towards the distal end, occurring in loose tufts attached by a small, polystromatic disc-like holdfast. Cells (up to 10 &m in diam.) arranged in fairly regular packets of 2's or 4's and embedded in a gelatinous matrix. A single parietal chloroplast, with a membrane-limited, embedded pyrenoid, visible in thin-sections only (Chen and others, 1974). Chrysolaminaran vacuoles and lipid droplets present. Zoospores formed singly from vegetative cells of mature thalli, about 10 &m in diam. with two, lateral, heterokont flagella. The anterior flagellum at least twice the length of the cell directs the cell forwards and bears tripartite mastigonemes; the shorter, posterior flagellum is acronematic. Zoospores negatively phototactic, with one chloroplast and a conspicuous stigma. No stomatocysts nor sexual reproduction recorded in culture. P. collinsii is a sublittoral marine alga, and generally occurs epiphytic on the leaves of the seagrass Zostera marina. An exclusively cold-water plant, it is distributed in boreal-arctic waters (northeast North America and northern Europe). Phaeosaccion was considered a member of the Phaeophyceae for almost a century. Morphological (McLachlan and others, 1971 ; Chen and others, 1974) and biochemical (Craigie and others, 1971) investigations definitely assigned this alga to the Chrysophyceae, where, with respect to size and morphology, P. collinsii is considered the largest and most advanced member. More data are needed to assess its true phylogenetic affinities.

Information contributed by: C. Billard. The most recent alteration to this page was made on 2021-10-20 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: Kawai, H. & Nakayama, T. (2015). Introduction (Heterokontobionta p.p.), Cryptophyta, Dinophyta, Haptophyta, Heterokontophyta (except Coscinodiscophyceae, Mediophyceae, Fragilariophyceae, Bacillariophyceae, Phaeophyceae, Eustigmatophyceae), Chlorarachniophyta, Euglenophyta. In: Syllabus of plant families. Adolf Engler's Syllabus der Pflanzenfamilien. Ed. 13. Phototrophic eukaryotic Algae. Glaucocystophyta, Cryptophyta, Dinophyta/Dinozoa, Haptophyta, Heterokontophyta/Ochrophyta, Chlorarachnniophyta/Cercozoa, Chlorophyta, Streptophyta p.p. (Frey, W. Eds), pp. 11-64, 103-139. Stuttgart: Borntraeger Science Publishers.

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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. 20 October 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 27 March 2023

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