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Electronic Flora of South Australia Species Fact Sheet

Dictyomenia tridens (Mertens ex Turner)Greville 1830: 1i.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Pterosiphonieae

Selected citations: J. Agardh 1841: 27; 1863: 1081; 1885: 105; 1897: 60. De Toni 1903: 985. De Toni & Forti 1923: 43. Falkenberg 1901: 287. Fuhrer et al. 1981: pl. 34. Guiler 1952: 105. Harvey 1855a: 538; 1863, synop.: xviii. Hooker & Harvey 1847: 397. Huisman 1997: 204; 2000: 163. Huisman & Walker 1990: 434. King et al. 1971: 124. Kützing 1849: 848; 1864: 33, pl. 94 f, g. Kylin 1956: 525. Lewis 1984: 53. Lucas 1909: 42; 1929b: 51. Lucas >& Perrin 1947: 281, fig. 128. May 1965: 396. Millar & Kraft 1993: 52. Reinbold 1898: 48. Schmitz & Falkenberg 1897: 445. Shepherd & Womersley 1971: 166; 1981: 367. Silva et al. 1996: 489. Sonder 1853: 697?; 1880: 33. Tate 1882a: 22. Tisdall 1898: 513. Wilson 1892: 167. Womersley 1950: 188.


Fucus tridens Mertens ex Turner 1819: pl. 255.

Rhodomela tridens (Mertens ex Turner)C. Agardh 1822: 373; 1824: 197.

Thallus (Fig. 150A) dark brown-red, erect, 10–40 cm high, complanately and irregularly marginally branched, with flat indeterminate branches 2–3 mm broad, above with a central midrib and reticulate surface pattern, bearing marginally short determinate branches 1–2 mm long, alternately positioned 1–3 mm apart, each with a broader base and tapering to 2–3 slender upper branches. Indeterminate lateral branches develop by continued growth of determinate laterals. Older indeterminate branches become denuded of the wings and the midrib thickened. Holdfast fibrous, 5–20 mm across, with terete branches; epilithic. Structure. Apical cell dome-shaped, 8–18 µm in diameter, segmenting transversely, with determinate laterals (2–) 3–4 cells apart (Fig. 150B), axial cells remaining conspicuous throughout the thallus. Indeterminate branches with 6 pericentral cells (Fig. 150C, D), 2 large lateral ones and 2 smaller ones on each surface, with the large lateral pericentral cells dividing laterally to form the flat branch and becoming corticated early between the pericentral cells and their derivatives (i.e. over the wings), more so over the midrib (Fig. 150D), especially below. Determinate laterals of clusters terete, with 5 (–6) pericentral cells, corticated. Trichoblasts occur near apices of determinate branches but readily caducous, branched, 1–2 mm long, basal and mid cells 20–30 µm in diameter and L/D (1–) 2–3. Cells uninucleate; rhodoplasts discoid.

Reproduction: Reproductive organs borne on branch clusters arising above lateral veins on the surface of main branches or as continued development of determinate laterals near apices.

Gametophytes dioecious. Procarps not observed. Carposporophytes with a small basal fusion cell and short, branched, gonimoblast filaments bearing elongate-clavate terminal carposporangia 30–55 µm in diameter. Cystocarps (Fig. 150E) ovoid to slightly urceolate, 800–1200 µm in diameter; pericarp ostiolate, corticated on mid and lower parts. Spermatangial organs (Fig. 150F) ovoid to elongate, 90–140 µm in diameter and 140–350 µm long, with 1–2 sterile basal cells and a uniseriate sterile apex 5–7 cells and 180–350 µm long.

Tetrasporangia (Fig. 150G) in the branched clusters on branch surface, branches terete, 180–230 µm in diameter, with segments L/D 0.5–1. Tetrasporangia in short series, one per segment, spirally arranged, 140–200 µm in diameter, with 2 cover cells.

Type from "Coast of New Holland" (Peron): probably from SE Australia; holotype in BM (illustrated by Turner).

Selected specimens: 7 mile beach, N of Dongara, W. Aust., drift (Womersley, 17.ix.1979; AD, A51377). Watermans, 20 km N of Perth, W. Aust., drift (Womersley, 20.viii.1979; AD, A50994). Head of Great Australian Bight, S. Aust., drift (Womersley, 4.ii.1954; AD, A19228). 4 km W of Waldegrave I., S. Aust., 30 m deep (Branden, 3.vii.1987; AD, A57605). Tapley Shoal, S. Aust., 10 m deep (Shepherd, 2.ii.1969; AD, A33481). Semaphore, S. Aust., 10 m deep (Branden, 19.vi.1975; AD, A46349). Victor Harbour, S. Aust., drift (Womersley, 24.vii.1949; AD, A11151). Bashams Beach, Port Elliot, S. Aust., drift (Womersley, 15.v.1985; AD, A56607 and 15.viii.1999; AD, A68324). Vivonne Bay, Kangaroo I., S. Aust., drift (Womersley, 14.i.1948; AD, A6898). D'Estrees Bay, Kangaroo 1., S. Aust., drift (Womersley, 23.viii.1963; AD, A26784). Robe, S. Aust., drift (Odic, 20.vii.1974; AD, A45365). Lawrence Rock, Portland, Vic., 20 m deep (Watson, 14.v.1969; AD, A34431). Port Phillip Heads, Vic., 22 m deep (Watson, 29.iii.1985; AD, A57046). San Remo, Vic., drift (Sinkora A1982; 27.xi.1974; AD, A62707). East Cove, Deal I., Bass Strait, 15 m deep (Shepherd & R. Lewis, 7.v.1974; AD, A45104).

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

Distribution: Houtman Abrolhos, W. Aust., to San Remo, Vic., Deal I., Bass Strait, and Twofold Bay, N.S.W. (Millar & Kraft 1993, p. 52); doubtfully further north (Lewis 1984, p. 53).

Taxonomic notes: Dictyomenia tridens is a deep-water alga on rough-water coasts along most of southern Australia.


AGARDH, C.A. (1822). Species Algarum. Vol. 1, Pt 2, pp. 169–398. (Berling: Lund.)

AGARDH, C.A. (1824). Systema Algarum. (Berling: Lund.)

AGARDH, J.G. (1841). In historiam algarum symbolae. Linnaea 15, 1–50, 443–457.

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

AGARDH, J.G. (1885). Till algernes systematik. VII. Florideae. Acta Univ. lund. 21, 1–120, Plate 1.

AGARDH, J.G. (1897). Analecta Algologica. Cont. IV. Acta Univ. lund. 33, 1–106, Plates 1, 2.

DE TONI, G.B. & FORTI, A. (1923). Alghe di Australia, Tasmania e Nouva Zelanda. Mem. R. Inst. Veneto Sci., Lett. Arti 29, 1–183, Plates 1–10.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3. pp. 775–1521 + 1523–1525. (Padua.)

FALKENBERG, P. (1901). Die Rhodomelaceen des Golfes von Neapel und der angrenzenden Meeres-abschnitte. Fauna und Flora des Golfes von Neapel. Monogr. 26. (Friedländer: Berlin.)

FUHRER, B., CHRISTIANSON, I.G., CLAYTON, M.N. & ALLENDER, B.M. (1981). Seaweeds of Australia. (Reed: Sydney.)

GREVILLE, R.K. (1830). Algae Britannicae. (Maclachlan & Stewart: Edinburgh.)

GUILER, E.R. (1952). The marine algae of Tasmania. Checklist with localities. Pap. Proc. R. Soc. Tasmania 86, 71–106.

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.)

HOOKER, J.D. & HARVEY, W.H. (1847). Algae Tasmanicae. Lond. J. Bot. 6, 397–417.

HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.

HUISMAN, J.M. (1997). Marine Benthic Algae of the Houtman Abrolhos Islands, Western Australia. In Wells, F.E. (Ed.) The Marine Flora and Fauna of the Houtman Abrolhos Islands, Western Australia, pp. 177–237. (W. Aust. Museum: Perth.)

HUISMAN, J.M. (2000). Marine Plants of Australia. (Univ. W. Aust. Press, Nedlands, W. Aust. & ABRS, Canberra, A.C.T.)

KÜTZING, F.T. (1849). Species Algarum. (Leipzig.)

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

KING, R.J., BLACK, J.H. & DUCKER, S. (1971). Port Phillip Bay Survey 2.8. Intertidal ecology of Port Phillip Bay with systematic lists of plants and animals. Mem. Natn. Mus., Vict. 32, 93–128.

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

LEWIS, J.A. (1984). Checklist and bibliography of benthic marine macroalgae recorded from northern Australia. I. Rhodophyta. Dept. Defence, Materials Res. Lab., Melbourne, Vic. Report MRL-R-912.

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. (1898). Die Algen der Lacepede und Guichen Bay (Süd Australien) und deren näherer Umgebung, gesammelt von Dr. A. Engelhart-Kingston. II. Nuova Notarisia 9, 33–54.

SCHMITZ, F. & FALKENBERG, P. (1897). Rhodomelaceae. In Engler, A. & Prantl, K., Die natürlichen Pflanzenfamilien. T.1. Abt. 2, pp. 421–480. (Englemann: Leipzig.)

SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1971). Pearson Island Expedition 1969.-7. The subtidal ecology of benthic algae. Trans. R. Soc. S. Aust. 95(3), 155–167.

SHEPHERD, S.A. & WOMERSLEY, H.B.S. (1981). The algal and seagrass ecology of Waterloo Bay, South Australia. Aquat. Bot. 11, 305–371.

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. (1853). Plantae Muellerianae. Algae. Linnaea 25, 657–709.

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

TATE, R. (1882a). A list of the charas, mosses, liverworts, lichens, fungs, and algals of extratropical South Australia. Trans. R. Soc. S. Aust. 4, 5–24.

TISDALL, H.T. (1898). The algae of Victoria. Rep. 7th Meet. Aust. Ass. Adv. Sci., Sydney, 1898, pp. 493–516.

TURNER, D. (1819). Fuci sive Plantarum Fucorum Generi a Botanicis Ascriptarum Icones Descriptiones et Historia. Vol. 4, pp. 1–153, Plates 197–258. (London.)

WILSON, J.B. (1892). Catalogue of algae collected at or near Port Phillip Heads and Western Port. Proc. R. Soc. Viet. 4, 157–190.

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. 150.

Figure 150 image

Figure 150   enlarge

Fig. 150. Dictyomenia tridens (A, AD, A56607; B, F, AD, A45365; C, G, AD, A68324; D, AD, A46349; E, AD, A50994). A. Habit. B. Apex of indeterminate branch with determinate laterals. C. Transverse section of young thallus showing axial and 6 pericentral cells (arrows to 4 smaller cells). D. Transverse section of central region of older axis. E. Cystocarp. F. Spermatangial organs on trichoblasts. G. Branches with tetrasporangia.

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