Electronic Flora of South Australia Species Fact Sheet

Ecklonia radiata (C. Agardh) J. Agardh 1848: 146; 1896: 28.

Phylum Phaeophyta – Order Laminariales – Family Alariaceae

Selected citations: Jennings 1967: 93. Womersley 1967: 248.

Thallus (Pl. 4 fig. 2; Fig. 120) dark brown, 0.3–2 m high, with a single stipe bearing a complanate blade with distinct laterals. Holdfast more or less conical, usually 5–10 cm across and high, with subdichotomous haptera 2–4 mm in diameter; epilithic. Stipe simple, terete, solid, 2–20 (–100) cm long, and 2–12 mm in diameter. Blade differentiating at its base, with laterals usually developing rapidly from meristems at their bases, more or less alternately distichous; central blade usually smooth, occasionally with surface spines, 1.5–8 (–10) cm broad. Laterals 5–20 (–40) cm long, 1–10 cm broad, basally narrowed, simple to lobed, smooth to corrugate and often spiny (especially in rough-water forms), margin usually spiny; spines broad-based, mostly 2–4 (–10) mm long. Structure of a central filamentous medulla and outer cellular cortex with a surface meristoderm; outer cells with numerous discoid phaeoplasts.

Reproduction: Reproduction by extensive, usually inconspicuous, sori (Fig. 1211) mostly on the central blade but often also on the laterals, ovate to irregular in shape; unilocular sporangia clavate, 30–55 µm long and 8–12 µ in diameter, accompanied by clavate paraphyses 50–70 p.m long and 4–7 µm in diameter.

Type from "New Holland"; in LIV.

Selected specimens: Red Bluff, Kalbarri, W. Aust.. upper sublittoral pools (Womersley, 15.ix.1979; ADU, A51289). Egg I., Isles of St Francis, S. Aust., 32–38 m deep (Shepherd, 11.i.1971; ADU, A3803I-spiny form). Pearson I., S. Aust., upper sublittoral (Specht, 17.ii.1960; ADU, A24505-spiny form). Memory Cove, S. of Port Lincoln, S. Aust., upper sublittoral (Womersley, 25.ii.1959; ADU, A22284-with surface spines on laterals). Brighton, S. Aust., drift (Womersley, May 1944; ADU, A1612—lanciloba form). Aldinga, S. Aust., upper sublittoral (Womersley, 24.x.1954; ADU, A57135-cultured for gametophytes-and 7.ix.1986; ADU, A57144). Victor Harbor, S. Aust., drift (Harris, May 1943; ADU, A1813). Portland, Vic. (N. side Lawrence Rock), 8–11 m deep (Watson, 2.ix.1971; ADU, A39684). Walkerville, Vic., drift (Pope & Bennett, 19.v.1949: ADU, Al2187). Munro Bight, Tasman Pen., Tas., 38 m deep (Brown, 23.x.1982; ADU, A55762). Byron Bay, N.S.W., 2–3 m deep (Silvester, 10.ix.1973: ADU, A44089).

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

Distribution: From Kalbarri and the Abrolhos Is, W. Aust. around southern Australia and Tasmania to Caloundra, Qld., common and often dominant in the upper sublittoral under moderate wave action, and deeper (to 44 m) on rough-water coasts.

New Zealand; South Africa.

Taxonomic notes: Gametophytes 100–400 µ across, from few to many celled, the female (Fig. 121J) with few branches, cells irregularly swollen, 12–30 µm in diameter, forming eggs in terminal cells, the male (Fig. 121K) much-branched, cells 4–8 (–10) µm in diameter, with small, lateral antheridia.

The synonymy of E. radiata was listed and discussed by Womersley (1967, p. 248).

E. radiata is a very variable species in form of the laterals and degree of surface spininess. The laterals are denser (but fewer) and are themselves often lobed, and usually with numerous surface spines, in plants from rough-water situations. Deep water specimens may be either spiny or relatively smooth-surfaced. Some specimens from Cosy Corner, S.W. West Aust., 2–5 m deep (Sanderson, 1.ix.1985; ADU, A56948) have the ends of the laterals proliferous and subdivided, almost hapteroid.

Gametophytes grown from Aldinga plants in 1954 were markedly larger and more branched than those reported by Jennings (1967).


AGARDH, J.G. (1848). Species, Genera et Ordines Algarum. Vol. 1. (Gleerup: Lund.)

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

JENNINGS, R. (1967). The development of the gametophyte and young sporophyte of Ecklonia radiata (C. Ag.) J. Ag. (Laminariales). J. R. Soc. W. Aust. 50, 93–96.

WOMERSLEY, H.B.S. (1967). A critical survey of the marine algae of southern Australia. II. Phaeophyta. Aust. J. Bot. 15, 189–270.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustrations in Womersley Part II, 1997: PLATE 4 fig. 2; FIGS 120, 121 I–K.

Plate 4 image

Plate 4   enlarge

PLATE 4 fig. 1. Lessonia corrugata at Safety Cove, Port Arthur, Tas. (ADU, A54525).>
Ecklonia radiata.

Figure 120 image

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Fig. 120. Ecklonia radiata. A. (ADU, A39684). Plant with smooth surfaced, elongate-linear laterals and active meristematic region. B. (ADU, A22284). Plants with numerous surface spines.

Figure 121 image

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Fig. 121. A–C. Lessonia corrugata (A, ADU, A54525; B,C, ADU, A35562). A. Transverse section of thallus with corrugations, cortex with mucilage cavities, and filamentous medulla. B. Transverse section of thallus showing position of a sporangial sorus. C. Detail of transverse section with unilocular sporangia and paraphyses, cortex, and filamentous medulla. D,E. Macrocystis pyrifera (ADU, A56452). D. Transverse section (diagrammatic) of stipe. E. Detail of transverse section of thallus with unilocular sporangia and paraphyses, cortex, and filamentous medulla. F–H. Macrocystis angustifolia ( F, ADU, A16088; G,H, ADU, A57134). F. Detail of transverse section of thallus with unilocular sporangia and paraphyses, cortex, and filamentous medulla. G,H. Gametophytes from culture, G female, H male. I–K. Ecklonia radiata (I, ADU, A57144; J,K, ADU, A57135). I. Detail of transverse section of thallus with unilocular sporangia and paraphyses, and cortex. J,K. Gametophytes from culture, J female, K male.

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