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Electronic Flora of South Australia Species Fact Sheet

Melanthalia obtusata (Labillardière) J. Agardh 1852: 614; 1876: 404.

Phylum Rhodophyta – Class Florideophyceae – Order Gracilariales – Family Gracilariaceae

Selected citations: De Toni 1900b: 422. Guiler 1952: 89. Harvey 1858: pl. 25; 1859b: 313. Kylin 1932: 58. Lucas 1929b: 49. Lucas & Perrin 1947: 183, fig. 51. May 1965: 391. Reinbold 1897: 51. Sonder 1853: 689; 1881: 22. Tisdall 1898: 508. Wilson 1892: 176. Womersley 1950: 169; 1966: 147.


Fucus obtusatus Labillardière 1807: 111, pl. 255. Turner 1811: 26, pl. 145.

Rhodomela obtusata (Labillardière) C. Agardh 1822: 383; 1824: 200.

Melanthalia billardieri Montagne 1843: 298. Kützing 1849: 784; 1869: 15, pl. 42a, b. Sonder 1855: 522.

Thallus (Fig. 9A) dark red-brown, drying darker to almost black, 10–40 cm high, subdichotomously and complanately branched from the margins, usually at intervals of 1–3 cm, branches strongly compressed (Fig. 9B), (1.5–) 2–3 (–4) mm broad, linear or with occasional marginal irregularities or constrictions (associated with new growth), raised centrally in surface view (elliptic to biconvex in transverse section), branch apices (Fig. 9C) with a distinct, broad, cap and 2–3 mm wide just below apex. Holdfast discoid, 5–15 mm across, bearing one to a few terete stipes; epilithic. Structure multiaxial, with sudden transition from densely protoplasmic cap cells (Fig. 9C) to clearer and larger medullary cells, pseudoparenchymatous throughout with small outer cortical cells, 3–5 µm in diameter and L/D 1–1.5, in anticlinal rows, the outer cells dividing obliquely longitudinally and then transversely, secondary pit-connections abundant, globules within the cells frequent; medullary cells 20–35 µm in diameter, walls 2–4 µm thick. Rhodoplasts discoid.

Reproduction: Female plants with 2-celled carpogonial branches borne near the branch margins on mid cortical supporting cells with closely adjacent cortical branches. Carposporophytes with a dense gonimoblast reticulum involving a small basal fusion cell and cell fusions with gametophytic cells, producing a dense tuft of erect gonimoblast filaments terminating in straight chains (Fig. 9E) of numerous ovoid to subspherical carposporangia 8–11 µm in diameter, maturing apically. Cystocarps (Fig. 9D) marginal or submarginal, often subopposite or clustered, hemispherical, 1–1.5 mm across; pericarp massive, with inner tangentially elongate cells and outer anticlinal cell rows 2–4 µm in diameter, with a prominent ostiole produced by breakdown of pericarp tissue. Spermatangia not observed.

Tetrasporangial nemathecia (Fig. 9F) shallow, inconspicuous, on upper branches below apices; tetrasporangia basally pit-connected to outer cortical cells among dense 2–4-celled paraphyses 30–40 µm long and 3–6 µm in diameter, sporangia elongate-ovoid to clavate, 25–30 µm long and 8–12 µm in diameter, irregularly cruciately divided.

Type from SE Tasmania (Labillardière); holotype in FI. Syntype in Herb. Montagne, PC.

Selected specimens: Pennington Bay, Kangaroo I., S. Aust., upper sublittoral, shaded (Womersley, 22.i.1948; AD, A6439). Toad Head, West I., S. Aust., 6–9 m deep (Shepherd, 15.i.1966; AD, A30169). 1.3 km off Middle Point, Cape Northumberland, S. Aust., 13 m deep (Shepherd, 19.iii.1974; AD, A44943). Nora Creina, S. Aust., upper sublittoral pool (Womersley, 26.i.1967; AD, A31644). Lady Julia Percy I., Vic., 19 m deep (Shepherd, 4.i.1968; AD, A32418). Point Roadknight, Vic., drift (Womersley, 6.vi.1953; AD, A18810). Port Phillip Heads, Vic., 10 m deep (Watson, 8.iii.1985; AD, A57039 -"Marine Algae of southern Australia" No. 306). Little Squally Cove, Deal 1., Bass Strait, 21 m deep (Houridis, 14.iii.1993; AD, A63281). Lady Bay, Southport, Tas., 3–5 m deep (Brown & Womersley, 28.x.1982; AD, A56507).

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

Distribution: Pennington Bay, Kangaroo I., S. Aust., to Port Phillip Heads, Vic. and Deal I., Bass Strait, and around Tasmania.

Taxonomic notes: M. obtusata is a deep-water species found on rough-water coasts.

Harvey (1858, pl. 25) distinguished var. intermedia, giving as synonyms M. abscissa as in Hooker & Harvey (1845, p. 548) and M. jaubertiana (as in Sonder 1853, p. 689). These names are here considered to apply to M. abscissa (Turner) Hooker & Harvey. M. obtusata has been recorded from New Zealand as varieties which are M. abscissa. May (1966, p. 18) also recorded it from New Caledonia, but this record is more likely to apply to one of the two New Caledonian species described by Kützing, both of which need investigation.


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

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

AGARDH, J.G. (1852). Species Genera et Ordines Algarum. Vol. 2, Part 2, pp. 337–720. (Gleerup: Lund.)

AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 — Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

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

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

HARVEY, W.H. (1858). Phycologia Australica. Vol. 1, Plates 1–60. (Reeve: London.)

HARVEY, W.H. (1859b). Algae. In Hooker, J.D., The Botany of the Antarctic Voyage. HI Flora Tasmaniae. Vol. II, pp. 282–320. (Reeve: London.)

HOOKER, J.D. & HARVEY, W.H. (1845). Algae Novae Zelandiae. Lond. J. Bot. 4, 521–551.

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

KÜTZING, F.T. (1869). Tabulae Phycologicae. Vol. 19. (Nordhausen.)

KYLIN, H. (1932). Die Florideenordnung Gigartinales. Lunds Univ. Årsskr. N.F. Avd. 2, 28 (8), 1–88, Plates 1–28.

LABILLARDIÈRE, J.J. (1807). Novae Hollandiae plantarum specimen. Vol. 2. (Huzard: Paris.)

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

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. natn. Herb. 3, 349–429.

MAY, V. (1966). Further records of algae from New Caledonia, collected by Mrs R. Catala. Contr. N.S.W. natn. Herb. 4, 17–18. MAllA, A. (1918). Saggio di Algologica Oceanica. Nuova Notarisia 29, Nos 626–660. MAllA, A. (1921). Saggio di Algologia Oceanica. Nuova Notarisia 32, 73–132 (Nos 738–769).

MONTAGNE, C. (1843). Quatrième centurie de plantes cellulaires exotiques nouvelles. Ann. Sci. Nat. Sér. 2, Bot. 20, 294–306.

REINBOLD, T. (1897). Die Algen der Lacepede und Guichen Bay und deren näherer Umgebung (Süd Australien), gesammelt von Dr. A. Engelhart-Kingston. Nuova Notarisia 8, 41–62.

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

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

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

TURNER, D. (1811). Fuci sive Plantarum Fucorum Generi a Botanicis Ascriptarum Icones Descriptiones et Historia. Vol. 3, pp. 1–148, Plates 135–196. (London.)

WILSON, J.B. (1892). Catalogue of algae collected at or near Port Phillip Heads and Western Port. Proc. R. Soc. Vict. 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.

WOMERSLEY, H.B.S. (1966). Port Phillip survey, 1957–1963: Algae. Mem. natn. Mus., Vict. No. 27, 133–156.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1996: FIG. 9.

Figure 9 image

Figure 9   enlarge

Fig. 9. Melanthalia obtusata (A–D, AD, A57039; E, F, AD, A56507). A. Habit. B. Transverse section of thallus. C. Longitudinal section of branch apex showing meristematic cap. D. Longitudinal median section of a cystocarp. E. Longitudinal section of carposporophyte with chains of carposporangia. F. Transverse section of thallus with a tetrasporangial nemathecium.

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