Electronic Flora of South Australia Species Fact Sheet

Sargassum paradoxum (R. Brown ex Turner) Hooker & Harvey 1847: 413.

Phylum Phaeophyta – Order Fucales – Family Sargassaceae

Selected citations: J. Agardh 1848: 302; 1872: 66; 1889: 68, pl. 20 figs 8–11. Grunow 1915: 358. Harvey 1860: 282. Sonder 1853: 672; 1855: 512.


Fucus paradoxus R. Brown ex Turner 1811: 49, pl. 156. Mertens 1819: 181.

Sargassum grande J. Agardh 1889: 72, pl. 22 figs 1–8.

Sargassum gunnianum J. Agardh 1889: 71, p1. 21 figs 13–19.

Sargassum membranaceum J. Agardh 1872: 68; 1889: 76, pl. 24 figs 8–13.

Sargassum undulatum J. Agardh 1872: 67; 1889: 73, pl. 22 figs 9–15.

Thallus (Fig. 161A) medium to dark brown, 20–100 (–150) cm long, with stipes 1–4 (–10) cm long, terete, simple or occasionally branched, 2–4 mm in diameter, with slight, irregular, branch residues, bearing apically 1–3 (–5) long primary branches. Holdfast discoid-conical, 5–15 (–25) mm across, usually with a single stipe; epilithic. Primary branches 20–100 (–150) cm long, with robust, three-sided (triquetrous) axes bearing tristichously arranged laterals. Laterals (lower) basally retroflex, simple, 5–10 (–20) cm long, 2–3 cm broad, costate, with strongly undulate margins which are usually spinous; upper laterals 2–5 cm long and (0.3–) 0.5–1 cm broad, margins usually not undulate but usually spinous or incised, rarely entire. Vesicles abundant on older thalli, shortly petiolate, subspherical, (3–) 4–10 mm in diameter, mucronate or with a small terminal leaflet.

Reproduction: Thalli dioecious or monoecious. Receptacles (Fig. 164A,B) largely female or male, in openly branched racemes on upper laterals, petiolate, simple, more or less terete, (3–) 5–10 (–15) mm long and 700–1500 µm in diameter, with scattered ostioles; female receptacles (Fig. 164A) terete below, slightly to moderately compressed or triquetrous above with scattered spines (prominent in some specimens); male receptacles (Fig. 164B) more or less terete throughout, with no or few spines. Conceptacles unisexual or occasionally bisexual, with simple paraphyses; oogonia sessile, ovoid, 200–300 µm long and (80–) 120–210 µ in diameter, few per conceptacle; antheridia sessile or on short, branched, paraphyses, ovoid, 20–25 µm long and 8–12 µ in diameter.

Type from (probably) Tasmania or Kent Islands, Bass Strait (R. Brown); in BM.

Selected specimens: Arno Bay, S. Aust., drift ( Womersley, 1.i.1951; ADU, A13818). Tiparra Reef, S. Aust., 5 m deep (Shepherd, 11.i.1978; ADU, A49402). N. Spencer Gulf, S. Aust., 8 m deep (Shepherd, 6.ix.1973; ADU, A44470). Investigator Str., S. Aust., 20 m deep, 35°09'S, 137°31'E (Watson, 7.i.1971; ADU, A38431). Tapley Shoal (off Edithburgh), S. Aust., 15 m deep (Shepherd, 2.ii.1969; ADU, A33546). Marino, S. Aust., drift (Womersley, 29.xi.1959; ADU, A23969). Middle R., Kangaroo I., S. Aust., drift ( Womersley, 13.i.1950; ADU, Al2665). Saunders Beach, Eastern Cove, Kangaroo I., S. Aust., upper sublittoral pools (Womersley, 21.xi.1968; ADU, A32918-"Marine Algae of southern Australia" No. 291). Pennington Bay, Kangaroo I., S. Aust., sublittoral fringe (Womersley, 29.xii.1948; ADU, A10533). Port Fairy, Vic., drift (Womersley, 25.i.1967; ADU, A31742). Crawfish Rock, Westernport Bay, Vic., 3 m deep (Watson, 23.ii.1969; ADU, A33598). Franklin Sound, Flinders I., Bass Str., 5 m deep (Watson, 13.xii. 1972; ADU, A43005). Leading Lights, Tamar Est., Tas., drift (Leering, 21.xi.1948; ADU, A56152). Missionary Bay, Bruny I., Tas., 6–8 m deep (Womersley, 15.i.1949; ADU, A 10172).

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

Distribution: From Arno Bay, S. Aust., to Westernport Bay, Vic. (to Eden, N.S.W.?-May 1939, p. 202), and around Tasmania. Recorded from Geraldton, W. Aust., by De Toni & Forti (1923, p. 66), but this record is doubtful.

Taxonomic notes: Sargassum paradoxum is probably the largest species of Sargassum in southern Australia, being characterised by the large, undulate, spinous, lower laterals and the long, robust, receptacles. Hooker & Harvey (1847, p. 413) first recognised that the female receptacles could be somewhat 3-angled above, with conical protruberances or spines, while the male receptacles are cylindrical and smooth, tending to be larger than the female. However, not all plants are dioecious, and thalli intermediate in sexuality appear to have receptacles intermediate in morphology. Some specimens have more prominent spines than others, and this is taken to be a variable character.

S. grande J. Agardh, from "Tasmania and southern Australia", is identical with S. paradoxum. The lectotype (Herb. Agardh, LD, 2147) from Tasmania has fairly mature, irregularly spiny, receptacles. There is no specimen named S. grande in Herb. Agardh with attached basal and upper parts.

S. gunnianum J. Agardh is based on 7 specimens in Herb. Agardh of R. Gunn, from Georgetown, Tasmania, but none have basal laterals. No. 2132 is selected as lectotype, but has fairly young receptacles; they are almost certainly the same as S. paradoxum.

S. membranaceum J. Agardh from Tasmania (Gunn), lectotype in Herb. Agardh, LD, 2238, appears to be the upper parts of S. paradoxum, with moderately compressed, spinous, receptacles.

S. undulatum J. Agardh from Tasmania (Gunn), lectotype Herb. Agardh, LD, 2154 (lower left) is represented in Herb. Agardh by only this one good fertile specimen; others consist of basal laterals only and must be disregarded. The receptacles illustrated by J. Agardh are young, and older receptacles on the lectotype are 2–5 mm long and similar to the female receptacles of S. paradoxum.


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

AGARDH, J.G. (1872). Till algernes systematik. Ada Univ. lund. 9(8), 1–71.

AGARDH, J.G. (1889). Species Sargassorum Australiae. K. Svenska Vetenskapsakad. Handl. 23(3), 1–133, Plates 1–31.

DE TONI, G.B. & FORTI, A. (1923). Alghe di Australia, Tasmania e Nouva Zelanda. Memorie R. Inst. veneto Sci. 29, 1–183.

GRUNOW, A. (1915). Additamenta ad cognitionem Sargassorum. Verh. Zool. -Bot. Wien 65, 329–448.

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

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

MAY, V. (1939). A key to the marine algae of New South Wales. Part. II. Melanophyceae (Phaeophyceae). Proc. Linn. Soc. N.S.W. 64, 191–215.

MERTENS, M. (1819). Sur plusieurs espêces de Fucus, nouvelles ou peu connues, observées dans la collection du Muséum. Mem. Mus. Natl Hist. Nat., Paris 5, 172–90, Plates 13–15.

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

SONDER, O.W. (1855). Algae annis 1852 et 1853 collectae. Linnaea 26, 506–528.

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

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 161A, 164A,B.

Figure 161 image

Figure 161   enlarge

Fig. 161. A. Sargassum paradoxum (ADU, A23969). B. Sargassum fallax from Hamelin Bay, W. Aust. (ADU, A34358).

Figure 164 image

Figure 164   enlarge

Fig. 164. Receptacles of species of Sargassum subgenus Arthrophycus. A,B. Sargassum paradavum (A, ADU, A23969; B, ADU, A43005). A. Largely female. B. Largely male. C–E. Sargassum fallax ( C, From type; D, ADU, A37370; E, ADU, A34230). C. Young receptacles. D. With smooth receptacles. E. Receptacles with awns. F,G. Sargassum vestitum ( F, ADU. A31733; G, ADU, A30086). F. Small receptacles. G. Large receptacles. H. Sargassum tristichum (ADU, A19552). With triquetrous receptacles.

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