Electronic Flora of South Australia Species Fact Sheet

Cystoseira trinodis (Forsskál) C. Agardh 1820: 67.

Phylum Phaeophyta – Order Fucales – Family Cystoseiraceae

Selected citations: Papenfuss & Jensen 1967: 21, fig. 1.


Cystophyllum onustum (Mertens) J. Agardh 1848: 230. Womersley 1967: 254.

Cystophyllum muricatum (Turner) J. Agardh 1848: 231. Harvey 1860: pl. 139. Lucas 1936: 74. Nizamuddin 1962b: 233, figs 1–21.

Thallus (Fig. 128B) medium brown, 20–60 (–100) cm long, much branched radially with several long primary branches from stipes 1–4 (–10) cm long. Holdfast discoid-conical, 1–2 cm across, with one to several stipes; epilithic. Primary branches 20–50 (–100) cm long, with radially arranged laterals bearing short, terete, simple or branched ramuli; basal ramuli usually crowded, simple or branched, terete (flat and leaf-like only in tropical-subtropical forms), 1–2 (–3) cm long and 0.5–1 mm in diameter; rhachis usually densely covered (especially near the base) with short, muricate, processes 0.5–1.5 mm long, each at first with a terminal cryptostomatum. Vesicles (Fig. 131E) formed within ramuli, single or in chains of 2–4, each ovoid to fusiform, 2–4 (–5) mm long and 0.5–1.5 (–2) mm in diameter, with a terminal awn and prominent cryptostomata. Growth from a single, three-sided, apical cell in an apical depression. Structure of a compact medulla of elongate cells and a cortex of isodiametric cells decreasing in size to the phaeoplastic meristoderm; slender hyphae present in medulla and inner cortex.

Reproduction: Thalli monoecious. Receptacles (Fig. 131E) developed from ends of ramuli or laterally below vesicles, terete to lanciform, 2–10 (–20) mm long and 0.5–1.5 mm in diameter, simple or once branched. Conceptacles (Fig. 131F) bisexual, with scattered ostioles and a basal group(s) of phaeophycean hairs; oogonia comparatively large, few per conceptacle and largely filling it, sessile and partly embedded in the conceptacle wall; oogonia 120–200 µm across and 100–150 µm high; antheridia usually near the ostiole, sessile or on branched paraphyses, ovoid, 30–40 µm long and 10–15 µ in diameter. Embryo with four primary rhizoids.

Type from the Red Sea; in C(?)

Selected specimens: Jacques Point, Kalbarri, W. Aust., upper sublittoral pools (Womersley, 15.ix.1979; ADU, A51281). Point Valliant, Two People Bay, W. Aust., in large pool (Womersley, 30.viii.1979; ADU, A50953). Wittelbee Point, near Ceduna, S. Aust., drift (Womersley, 22.i.1951; ADU, A13704). Kellidie Bay, Coffin Bay, S. Aust., upper sublittoral (Womersley, 10.i.1987; ADU, A57369). Fisherman Bay (Port Broughton), S. Aust., drift (Womersley, 10.ix.1963; ADU, A26734). Aldinga, S. Aust., upper sublittoral pools near shore (Womersley, 3.xii.1986; ADU, A57282-"Marine Algae of southern Australia" No. 274). Petrel Cove, Victor Harbor, S. Aust., in sheltered pools ( Womersley, 10.xii.1944; ADU, A1596). Pennington Bay, Kangaroo I., S. Aust., in rear reef pools ( Womersley, 28.i.1946; ADU, A2831). American R. inlet, Kangaroo I., S. Aust., 0.5–1 m deep ( Womersley, 26.i.1946; ADU, A3160).

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

Distribution: Indian Ocean tropics and subtropics; Indonesia; northern Australia.

The form without broader basal laterals extends from Kalbarri, W. Aust. around southern Australia to Victor Harbor, S. Aust.

Taxonomic notes: Nizamuddin (1962) and Papenfuss & Jensen (1967) have shown that C. trinodis is closer to Cystoseira in anatomical and reproductive features (Fensholt 1955) than to Myagropsis Kützing (over which Cystophyllum has been conserved).

Southern Australian plants here ascribed to Cystoseira trinodis have only very slender, almost terete, lower "leaves", never the 2–4 mm broad ones found in the more typical tropical or subtropical plants of this species (Nizamuddin 1962, p. 233; Womersley 1967, p. 255). However, these two forms are otherwise very similar, and for the present the southern Australian "leaf-less" plants are regarded as a cooler water form of the species. Roberts (1978, pp. 405, 418) discussed similar variation in the basal "leaves" of C. foeniculacea and C. humilis, and regarded it as of subspecific importance.

Should the southern Australian form ever be shown to be a distinct species, it will have to be given a new name since the other synonyms of C. trinodis are based on "leafy" plants and the type of C. onustum has no basal parts but is probably of the "leafy" form.


AGARDH, C.A. (1820). Species Algarum. Vol. 1, Part 1, Fucoideae, pp. 1–168. (Lund.)

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

FENSHOLT, D.E. (1955). An emendation of the genus Cystophyllum (Fucales). Am. J. Bot. 42, 305–22.

HARVEY, W.H. (1860). Phycologia Australica. Vol. 3, Plates 121–180. (Reeve: London.)

LUCAS, A.H.S. (1936). The Seaweeds of South Australia. Part 1. Introduction and the Green and Brown Seaweeds. (Govt Printer: Adelaide.)

NIZAMUDDIN, M. (1962b). Studies on Cystophyllum muricatum (Turner) J. Agardh, 1848. New Phytol. 61, 233–243.

PAPENFUSS, G.F. & JENSEN, J.B. (1967). The morphology, taxonomy and nomenclature of Cystophyllum trinode (Forsskål) J. Agardh and Cystoseira myrica (S.G. Gmelin) C. Agardh (Fucales: Cystoseiraceae). Blumea 15, 17–24, Figs 1–4.

ROBERTS, M. (1978). Active speciation in the taxonomy of the genus Cystoseira C. Ag. In Irvine, D.E.G. & Price, J.H. (Eds) Modern approaches to the taxonomy of red and brown algae. Systematics Association Special Vol. 10, pp. 399–422. (Academic Press: London.)

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: FIGS 128B, 131E,F.

Figure 128 image

Figure 128   enlarge

Fig. 128. A. Hormophysa triquetra (ADU, A26730). B. Cystoseira trinodis (ADU, A26734).

Figure 131 image

Figure 131   enlarge

Fig. 131. A,B. Scaberia agardhii (ADU, A57281). A. Upper branches of thallus with peltate laterals and vesicles (lower right). B. Cross section of branch with conceptacles and a vesicle. C,D. Hormophysa triquetra (ADU, A57314). C. Cross section of branch with central vesicle and conceptacles. D. Section of vesicle wall with a bisexual conceptacle and a strand of small cells. E,F. Cystoseira trinodis (ADU, A57282). E. Upper branches with vesicles and receptacles. F. Cross section of receptacle with bisexual conceptacles.

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