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Polysiphonia senticulosa Harvey 1862b: 169.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae

Selected citations: J. Agardh 1863: 974. Kudo & Masuda 1988: 138, figs 1–9. Scagel et al. 1989: 235.


Polysiphonia pungens Hollenberg 1942a: 774, figs 1, 10. Lewis 1983: 262. Womersley 1979: 472, fig. 3A–D.

Thallus (Fig. 79A) dark red-brown, 5–18 cm high, slender and lax, much branched, arising from slight prostrate and entangled basal filaments. Attachment by rhizoids from prostrate filaments; epiphytic and probably epilithic. Structure. Prostrate filaments 250–350 µm in diameter with segments L/D 0.4–1, with scattered rhizoids in open connection with the pericentral cells; erect main filaments 180–250 µm in diameter with segments L/D 4–12 below, tapering gradually to 100–150 µm in diameter above with segments mostly L/D 1–3 (–4), irregularly branched; branches near apices arising exogenously prior to pericentral cell formation and usually every 2–7 segments, independent of trichoblasts, spirally arranged on a phyllotaxis of about 1/4, with most remaining as simple, determinate, gently tapering and acuminate (Fig. 79D) branchlets (30–) 50–100 (–120) µm in diameter, with segments L/D 0.5–1 which when mature are usually markedly shorter than segments of the parent branch; some branchlets continuing as indeterminate apices; accessory indeterminate branches also occasionally arising endogenously in branch axils from the first axial cell of the branch, or rarely from other axial cells. Pericentral cells 4, ecorticate; trichoblasts and scar cells absent or usually very rare in vegetative and tetrasporangial thalli; in sexual plants trichoblasts bear the reproductive organs, slender, with 1–3 branches. Rhodoplasts discoid to lobed or ribbon like, irregularly arranged.

Reproduction: Gametophytes dioecious. Carposporophytes with a small basal fusion cell and short gonimoblast bearing clavate terminal bearing carposporangia 20–40 µm in diameter. Cystocarps (Fig. 79B) short-stalked, ovoid to urceolate, with the neck prominent and spreading when mature, 200–570 µm in diameter; pericarp 2 cells thick, outer cells isodiametric to slightly transversely elongate. Spermatangial branches (Fig. 79C) 250–350 µm long and 40–50 µm in diameter, replacing the whole trichoblast and with a sterile tip 5–7 cells long.

Tetrasporangia (Fig. 79D) forming a straight series in lesser branchlets, swelling the branch evenly above the sterile basal segments, 60–90 µm in diameter.

Type from Orcas I., Washington, U.S.A. (Lyall); holotype in BM.

Selected specimens: Apollo Bay, Vic., on Sargassum vestitum on pipeline (just subsurface) in dock (Owen, 1.ix.1971; AD, A39494). Kirk Point, Port Phillip, Vic., drift (Womersley, 11.viii.1970; AD, A36032 and 30.viii.1971; AD, A39519). Williamstown, Vic., lower eulittoral (King, 28.viii.1969; AD, A39493, MEL, 45986 and MELU, 4613). Breakwater Pier, Hobsons Bay, Vic., on mussels (J. Lewis, 3.ix.1976; AD, A49786). Ricketts Point, Port Phillip, Vic., lower eulittoral (King, 30.ix.1969; MEL, 45988 and MELU, 4697).

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

Taxonomic notes: Distribution: In southern Australia from harbours in Victoria.
NW North America. Japan (Yoshida 1999, p. 1071).

Kudo & Masuda (1988) have shown that P. pungens Hollenberg is synonymous with P. senticulosa Harvey. Kylin (1941, p. 35, pl. 11 fig. 33) placed the latter as the type of a new genus, Orcasia, due to the endogenous origin of accessory branches (see also Kylin 1956, p. 503). The genus Orcasia has not been recognised by other authors (e.g. Scagel et al. 1989) but the endogenous axillary branching may well be a distinctive feature.

The disparate distribution, and the occurrence in Australia mainly in the harbour of Port Phillip, indicates it may be an adventive, spread by shipping.


AGARDH, J.G. (1863). Species Genera et Ordines Algarum. Vol. 2, Part 3, pp. 787–1291. (Gleerup: Lund.)

HARVEY, W.H. (1862b). Notice of a collection of Algae made on the North-West Coast of North America, chiefly at Vancouver's Island, by David Lyall ... in the years 1859–61. J. Proc. Linnean Soc. Bot. 6, 157–177.

KUDO, T. & MASUDA, M. (1988). Taxonomic notes on Polysiphonia senticulosa Harvey and P. pungens Hollenberg (Ceramiales, Rhodophyta). Jpn. J. Phycol. (Sôrui) 36, 138–142.

KYLIN, H. (1941). Californische Rhodophyceen. Lunds Univ. Årsskr. N.F. Avd. 2, 37 (2), 1–51, Plates 1–13.

KYLIN, H. (1956). Die Gattungen der Rhodophyceen. (Gleerups: Lund.)

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.

SCAGEL, R.F., GABRIELSON, P.W., GARBARY, D.J. et al. (1989). A synopsis of the benthic marine algae of British Columbia, Southeast Alaska, Washington and Oregon. Univ. Brit. Columbia, Vancouver, B.C., Phycological Contr. No. 3.

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. 79 A–D.

Figure 79 image

Figure 79   enlarge

Fig. 79. A–D. Polysiphonia senticulosa (AD, A36032). A. Habit. B. Cystocarp. C. Spermatangial branches. D. Tetrasporangial branches. E. Polysiphonia brevisegmenta (AD, A32615). Branches bearing cystocarps. F, G. Polysiphonia amphibolis (F, AD, A32838; G, AD, A42525). F. Habit, on stems of Amphibolis. G. Thallus, with prostrate axes bearing erect branches. (All as in Womersley 1979, courtesy of Aust. J. Bot.)

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