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Polysiphonia constricta Womersley 1979: 497, fig. 11F–H.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Selected citations: Adams 1983: 2; 1994: 325. Lewis 1983: 262. Millar 1990: 442, fig. 65A–D? Millar & Kraft 1993: 57.

Thallus (Fig. 87F) brown-red, 5–12 cm high, tufted, with an erect basal axis arising from a short prostrate filament, branched above subdichotomously to alternately with upper parts densely fibrilliferous to fastigiate. Attachment by rhizoids from prostrate base; probably epilithic. Structure. Prostrate base only a few mm long, 200–700 µm in diameter with segments L/D 0.3–0.7 (–1), attached by unicellular rhizoids cut off from pericentral cells; erect lower axis 300–800 µm in diameter with segments L/D 0.4–1, tapering gradually to 200–400 µm in diameter with segments L/D (0.3–) 0.5–0.8 (–1.8) in mid parts and to (60–) 75–100 µm in diameter with segments L/D 0.8–1 in branchlets; lateral branchlets, especially those unbranched or virtually so, usually markedly basally constricted (Fig. 87G), mostly 0.5–1 mm long and 70–150 µm in greatest diameter; apices straight, with few, inconspicuous trichoblasts; lateral branches arising from the basal cell of trichoblasts but remainder of trichoblast soon lost, with occasional cicatrigenous branchlets. Pericentral cells 7, elongate except close to apices, ecorticate throughout, much slenderer for 2–3 segments at base of constricted branchlets; trichoblasts and scar cells occasional, trichoblasts slender, often relatively undeveloped, 1–3 times furcate. Rhodoplasts discoid, scattered or in slight chains.

Reproduction: Sexual reproduction unknown.

Tetrasporangia (Fig. 87H) formed in linear series (usually adaxial) in lesser branchlets, often extending below 1–2 branchings, slightly but evenly distorting the segments on one side of the branchlet, subspherical to ovoid, 40–60 µm.

Type from Muston, American R. inlet, Kangaroo I., S. Aust., 2–3 m deep (Womersley, 21.xi.1968); holotype in AD, A32927.

Selected specimens: Mt Dutton Bay, Coffin Bay, S. Aust, 5 m deep (Womersley, 1.xii.1975; AD, A46810). Tapley Shoal, Gulf St Vincent, S. Aust., 13 m deep (Shepherd, 5.ii.1969; AD, A33772). West Beach, S. Aust., drift (Womersley, 1.xii.1946; AD, A4513). Muston, Kangaroo I., S. Aust., 2–3 m deep (Kraft, 7.iv.1972; AD, A42411). American R. inlet, Kangaroo I., S. Aust., on outer black buoy (Womersley, 15.i.1948; AD, A9487). Bay of Shoals, Kangaroo I., S. Aust. (AD, A2634). 4 km off Seacliff, S. Aust., 13 m deep on shell (Rowland, 5.iii.1988; AD, A58637). Hobson Bay, Port Phillip, Vic., 0.5 m deep on power station water outlet (Watson, 2.v.1972; AD, A42354). Crawfish Rock, Westernport Bay, Vic., 2 m deep (Watson, 28.v.1974; AD, A45379).

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

Distribution: Coffin Bay, S. Aust. to Crawfish Rock, Westernport Bay, Victoria. N.S.W.? (see Millar 1990, p. 443 and Millar & Kraft 1993, p. 57).

New Zealand (Adams 1983, p. 2).

Taxonomic notes: P. constricta is a distinctive species in southern Australia, separated from the other species (P. decipiens) with 7 pericentral cells by its habit (without short patent laterals) and by the usual strong basal constriction of the young branchlets. The type and most specimens are sterile, but it is possible that the constricted, usually more densely protoplasmic branchlets could act as propagules. P. constricta is confined to very sheltered waters in bays and inlets.

Specimens from Coffin Bay, S. Aust. (AD, A46810) and Hobson Bay, Port Phillip, Vic. (AD, A42354 and MELU, L1065–6, L1073, L1086) agree well with P. constricta except for the absence of laterals with constricted bases. Of these, A42354 is tetrasporangial. Further study is needed on such specimens in relation to the type, but if they do prove to be the same species it is possible that sterile plants bear constricted laterals which can propagate the plants, while fertile plants do not bear such laterals. Further study is also needed of N.S.W. plants referred to this species.

Some other specimens with 7 pericentral cells are at present referred to P. isogona Harvey (see below). These differ from P. constricta in being slenderer plants with numerous axes from prostrate entangled filaments, not having markedly constricted branch bases and in having more frequent trichoblasts or scar cells.


ADAMS, N.M. (1983). Checklist of marine algae possibly naturalised in New Zealand. N.Z. J. Bot. 21, 1–2.

ADAMS, N.M. (1994). Seaweeds of New Zealand. (Cant. Univ. Press: Christchurch.)

LEWIS, J.A. (1983). Floristic composition and periodicity of subtidal algae on an artifical structure in Port Phillip Bay (Victoria, Australia). Aquatic Bot. 15, 257–274.

MILLAR, A.J.K. & KRAFT, G.T. (1993). Catalogue of marine and freshwater Red Algae (Rhodophyta) of New South Wales, including Lord Howe Island, South-western Pacific. Aust. Syst. Bot. 6, 1–90.

MILLAR, A.J.K. (1990). Marine Red Algae of the Coffs Harbour Region, northern New South Wales. Aust. Syst. Bot. 3, 293–593.

WOMERSLEY, H.B.S. (1979). Southern Australian species of Polysiphonia Greville (Rhodophyta). Aust. J. Bot. 27, 459–528.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 2003: FIG. 87 F–H.

Figure 87 image

Figure 87   enlarge

Fig. 87. A–E. Polysiphonia brodiei (A, B, E, AD, A49156; C, D, AD, A44594). A. Habit. B. Young cortication. C. Branches with cystocarps. D. Spermatangial branches. E. Tetrasporangial branches. F–H. Polysiphonia constricta (F, G, AD, A32927; H, AD, A42354). F. Habit. G. Branch with basally constricted laterals. H. Tetrasporangial branches. (All as in Womersley 1979, courtesy of Aust. J. Bot.)

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