Electronic Flora of South Australia Genus Fact Sheet

Genus SCYTOSIPHON C. Agardh 1820: 160, nom. cons.

Phylum Phaeophyta – Order Scytosiphonales – Family Scytosiphonaceae

Thallus (potential gametophyte) elongate, linear, simple, usually 10–30 cm high and 1–5 mm broad, terete, often constricted at intervals, or compressed, hollow (or with sides adjacent but not united), with one to numerous fronds from a small discoid holdfast. Growth diffuse. Structure polystichous, with a medulla of large, irregular, clear cells, 2–4 (–6) cells thick, and a 1–2 cell thick cortex of small cells, each with a single phaeoplast and a pyrenoid, with abundant, scattered, groups of phaeophycean hairs. Alternate stage (potential sporophyte) filamentous or crustose, haplostichous, with a base of radiating filaments, each cell bearing a short, erect filament (corresponding to Ralfsia clavata).

Reproduction: The erect phase with extensive sort of plurilocular organs, accompanied by unicellular, elongate, paraphyses, forming zooids which reproduce the erect thallus directly, or via a filamentous or discoid stage, or act as gametes (slightly anisogamous). The discoid stage producing unilocular sporangia, with zooids giving rise to the erect stage.

Life history plastic, depending on conditions of day-length and temperature; diplohaplontic and heteromorphic, or direct from the erect phase.

Type species: S. lomentaria (Lyngbye) Link, type cons.

Taxonomic notes: A genus of several taxa, most of which may be forms of the type species (Clayton 1976a, p. 207). The life history of Scytosiphon has been studied in detail in various parts of the world. The plastic life history (Clayton 1976a,b, 1980) appears to be an alternation of the potentially gametophytic erect winter phase with the sporophytic summer phase (identical with the subgenus Stragularia of Ralfsia), but with direct reproduction of the erect phase under certain conditions.

References:

AGARDH, C.A. (1820). Species Algarum. Vol. 1, Part 1, Fucoideae, pp. 1–168. (Lund.)

CLAYTON, M.N. (1976a). The morphology, anatomy and life history of a complanate form of Scytosiphon lomentaria (Scytosiphonales, Phaeophyta) from southern Australia. Mar. Biol. (Berl.) 38, 201–208.

The Marine Benthic Flora of Southern Australia Part II complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
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