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Electronic Flora of South Australia Species Fact Sheet

Sphacelaria biradiata Askenasy 1894: 15, pl. II fig. 12.

Phylum Phaeophyta – Order Sphacelariales – Family Sphacelariaceae

Selected citations: Sauvageau 1901: 418(R166), fig. 38; 1903: 54 (R238). Womersley 1967: 195.


S. harvevana Sauvageau 1902: 380 (R193). Womersley 1967: 199.

Thallus (Figs 51B, 53A) medium brown, 0.2–1.0 (–1.5) cm long, forming loose to (usually) dense, much branched, tufts or mats on larger algae (especially Fucales) or seagrasses, with many axes arising from a compact, cellular-filamentous base on the host surface. Branching (Fig. 53A,B) of main axes frequent, irregularly radial, alternate or occasionally opposite, with 2–3 orders of largely determinate laterals each slenderer than the parent branch and arising at moderate to broad angles; phaeophycean hairs abundant, 12–18 µm in diameter. Axes (Fig. 53B,F) (40–) 50–80 (–90) µm in diameter with segments L/B (0.5–) 0.6–0.8 (–1.0) and showing (3–) 4–7 (–11) longitudinal walls (Fig. 53F); laterals 25–40 (–45) µm in diameter with segments

L/B (0.4–) 0.6–1.0 (–1.2) and showing 2–4 (–5) longitudinal walls; secondary transverse walls absent except where lateral branches or reproductive structures arise; pericysts frequent.

Reproduction: Propagula (Fig. 53C–E) with two arms, each basally constricted and tapering above, straight to curved, 80–160 (–200) pm long and (20–) 25–40 µm in maximum diameter, borne on a pedicel 80–160 µm long, and with a long apical hair 8–12 µ in diameter. Unilocular sporangia (Fig. 53B,F) scattered, with a short, unicellular pedicel, subspherical, (50–) 60–80 µm in diameter. Plurilocular organs (Fig. 53G) scattered, borne on pedicels 1–3 cells long, ovoid to obovoid, 40–60 (–75) µm long and 30–40 (–60) µm in diameter, with small loculi.

Type from "Adelaide", S. Aust. on Laurencia; in B?

Selected specimens: Green I., Rottnest I., W. Aust., on Posidonia sinuosa, 1–2 m deep (Walker, 24.ix.1985; ADU, A56783). Meelup, Cape Naturaliste, W. Aust., on Cystophora brownii, upper sublittoral (Mitchell, 23.ix.1966; ADU, A31175). Aldinga, S. Aust., on Cystophora subfarcinata in outer reef pools (Womersley, 17.ix.1966; ADU, A30715). Pennington Bay, Kangaroo I., S. Aust., on Cystophora in reef pools (Womersley, 1.xi.1947; ADU, A6099). Nora Creina, S. Aust., on Sargassum decipiens in reef pools (Womersley, 26.i.1967; ADU, A31645). Carpenter Rocks , S. Aust., on Sargassum decipiens, upper sublittoral pools (Womersley, 5.ii.1970; ADU, A35177-"Marine Algae of southern Australia" No. 31). Apollo Bay, Vic., on Cladostephus, upper sublittoral (Womersley, 12.iv.1959; ADU, A22652). Walkerville, Vic., on Caulocystis, upper sublittoral (Sinkora A1491, 22.ii.1972; ADU, A42269). White Beach, Wedge Bay, S.E. Tas., on Sargassum verruculosum, upper sublittoral (Wollaston & Mitchell, 29.ii.1964; ADU, A27682). Stewarts Bay, Port Arthur, Tas., on Heterozostera, drift (Womersley, 30.x.1982; ADU, A55781).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: From Rottnest I., W. Aust., around southern Australia and Tasmania to Walkerville, Vic.

Taxonomic notes: S. biradiata is the commonest epiphytic Sphacelaria on southern Australian coasts, occurring on many larger Fucales and cartilaginous red algae, as well as on seagrasses. It is closely related to S. cirrosa but is distinct in having only two arms to the propagula, formed simultaneously, and also has more irregular branching. In S. hiradiata, plurilocular organs with only small loculi are known, but the nature of the zooids is unknown. Propagula on plants also bearing either plurilocular organs or unilocular sporangia are known at most times of the year.

S. harvevana Sauvageau, with the type from Cape Riche, W. Aust., on Cystophora (Harvey), bearing unilocular sporangia, is based on small plants typical of S. hiradiata but not bearing propagula.


ASKENASY, E. (1894). Ober einige australische Meeresalgen. Flora 78, 1–18, Plates 1–4.

WOMERSLEY, H.B.S. (1967). A critical survey of the marine algae of southern Australia. II. Phaeophyta. Aust. J. Bot. 15, 189–270.

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
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustration in Womersley Part II, 1997: FIGS MB, 53 A–G.

Figure 53 image

Figure 53   enlarge

Fig. 53. A–G. Sphacelaria biradiata (A,B,E,F, ADU, A30715; C,D,G, ADU, A31645). A. Branching pattern of thallus. B. Branch with laterals, phaeophycean hairs and unilocular sporangia. C–E. Propagula, young, medium and mature. F. Branch with unilocular sporangia. G. Branch with plurilocular sporangia. H–K. Sphacelaria cirrosa (ADU, A30858). H. Branching pattern of thallus. I. Branch with propagula. J. Axes with laterals and unilocular sporangia. K. Branch with unilocular sporangia.

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