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Platysiphonia mutabilis (Harvey) Womersley & Shepley 1959: 209.

Phylum Rhodophyta – Family Sarcomeniaceae

Selected citations: May 1965: 377. Millar & Kraft 1993: 48. Shepherd 1983: 83. Silva et al. 1996: 465.


Polysiphonia mutabilis Harvey 1855a: 540. Kützing 1864: 20, pl. 55 d-g.

Sarcomenia mutabilis (Harvey) J. Agardh 1863: 1261; 1896: 134. Børgesen 1931 b: 8. De Toni 1900: 736. Harvey 1863, synop.: xvii. Lucas 1909: 37.; 1929b: 50. Lucas & Perrin 1947: 234. Reinbold 1899: 46. Sonder 1880: 33. Tisdall 1848: 513. Womersley 1950: 184. Womersley & Shepley 1959: 187, figs 55, 56, p1. 3 fig. 2.

Thallus (Fig. 74A) medium to dark red-brown, 4–10 cm high, much branched with slender branches corticated only near their base. Attachment by a rhizoidal holdfast; epiphytic. Structure. Apical cell hemispherical, with axial cells producing 4 pericentral cells, the abaxial one first, followed by the lateral cells then the adaxial pericentral cell, with each lateral cell cutting off 2 flanking cells giving a compressed branch 5 cells broad. Mid blades 80–140 µm broad, segments L/D 0.6–1. Lower corticated axes 0.7–1.5 mm thick. Branches arise endogenously from the axial cells, with their basal 1–2 segments usually lacking flanking cells. Cortication (Fig. 74C) is slight above by small cells cut off from pericentral cells and becomes complete and moderate only on lower parts of older branches. Cells uni- to multinucleate; rhodoplasts discoid, becoming chained.

Reproduction: Gametophytes dioecious. Procarps adaxial on lateral branches, with the adaxial pericentral cell cutting off sterile cells and a 4-celled carpogonial branch. Carposporophytes with a small basal fusion cell and branched gonimoblast filaments bearing elongate-ovoid to clavate terminal carposporangia 16–22 µm in diameter. Cystocarps (Fig. 74B) sessile, ovoid, 500–700 µm in diameter. Pericarp with about 16 erect filaments, each cell producing 2 transversely elongate outer cells, slightly corticated only at the base. Spermatangia (Fig. 74C) covering the lower part of laterals, the fertile part 1–1.5 mm long and 180–220 µm broad, with spermatangia produced from the lateral pericentral cells, the transverse pericentral cells and flanking cells remaining sterile.

Tetrasporangia (Fig. 74D) borne in lateral blades 0.5–1.2 mm long and 100–180 µm broad, with 2 rows of tetrasporangia derived from the lateral pericentral cells which form a cover cell on each side, with each flanking cell dividing horizontally into 2; tetrasporangia 30–45 µm in diameter.

Type: From Fremantle, W. Aust., on "Zostera" (= Posidonia); lectotype in Herb. Harvey, TCD (Alg. Aust. Exsicc. 116A).

Selected specimens: Yanchep, W. Aust., on Amphibolis, drift (Womersley, 22.ix.1979; AD, A51272). Safety Bay, W. Aust., on Amphibolis, drift (Womersley, 29.ix.1979; AD, A50737 – “Marine Algae of southern Australia” No. 208). N Spencer Gulf, S. Aust., 11 m deep (Shepherd, 5.ix.1973; AD, A44226). Sturt Bay, S. Aust., on a fucoid alga (Davey; AD, A1137). Seal Bay, Kangaroo I., S. Aust., in pools on outer reef (Womersley, 29.x.1966; AD, A30848). Stinky Bay, Nora Creina, S. Aust., on Codium galeatum, drift (Abbott, 7.xi.1965; AD, A29697). Shoreham, Western Port, Vic., drift (Sinkora A1306, 29.x.1971; AD, A62753). Low Head, Tas., drift (Perrin, Nov. 1949; AD, A16465).

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

Distribution: Yanchep, W. Aust., to Port Stephens, NSW and N Tasmania.

Taxonomic notes: Børgesen (1931b, p. 8) first stated that S. mutabilis could be referred to Platysiphonia, but did not validate the transfer.


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

AGARDH, J.G. (1896). Analecta Algologica. Cont. III. Acta Univ. lund. 32, 1–140, Plate 1.

BØRGESEN, F. (1931b). Sur Platysiphonia nov. gen. et sur les organes mâles et femelles du Platysiphonia miniata (Ag.) nov. comb. (Sarcomenia miniata (Ag.) J.Ag.) Recueil Tray. Crypt. ded. Louis Mangin, pp. 21–29.

DE TONI, G.B. (1900). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2. pp. 387–776. (Padua.)

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

KÜTZING, F.T. (1864). Tabulae Phycologicae. Vol. 14. (Nordhausen.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

LUCAS, A.H.S. (1929b). A census of the marine algae of South Australia. Trans. R. Soc. S. Aust. 53, 45–53.

MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S. W. Natl Herb. 3, 349–429.

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.

REINBOLD, T. (1899). Meeresalgen von Investigator Street (Süd Australien), gesammelt von Miss Nellie Davey (Waltham, Honiton). Hedwigia 38, 39–51.

SHEPHERD, S.A. (1983). Benthic communities of upper Spencer Gulf, South Australia. Trans. R. Soc. S. Aust. 107, 69–85.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (Univ. California Press: Berkeley.)

SONDER, O.W. (1880). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1959). Studies on the Sarcomenia group of the Rhodophyta. Aust. J. Bot. 7, 168–223.

WOMERSLEY, H.B.S. (1950). The marine algae of Kangaroo Island. III. List of Species 1. Trans. R. Soc. S. Aust. 73, 137–197.

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. 74.

Figure 74 image

Figure 74   enlarge

Fig. 74. Platysiphonia mutabilis (A, AD, A44226; B–D, AD, A29697). A. Habit. B. Cystocarps. C. Spermatangial branches with corticated branch on left. D. A stichidium.

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