Electronic Flora of South Australia Species Fact Sheet

Sargassum decurrens (R. Brown ex Turner) C. Agardh 1820: 42.

Phylum Phaeophyta – Order Fucales – Family Sargassaceae

Selected citations: J. Agardh 1872: 53; 1889: 47, pl. 15 figs 6,7. De Toni & Forti 1923: 64. Grunow 1915: 334. Harvey 1860: pl. 145. Womersley 1954b: 343, pl. 2 fig. 1.

Synonyms

Fucus decurrens R. Brown ex Turner 1811: pl. 194.

Sargassum scabripes J. Agardh 1872: 52; 1889: 48, pl. 2.

Thallus (Fig. 157A) medium brown, (10–) 20–50 cm long, with a simple or branched stipe 1–8 cm long, slightly compressed and 2–4 mm broad, verrucose with branch residues, bearing apically one to several primary branches. Holdfast discoid-conical, 5–15 mm across, with usually a single, occasionally branched, stipe; epilithic. Primary branches distichous, complanately branched, axes 5–12 mm broad below, winged, with a prominent midrib, producing laterals marginally and alternately. Laterals simple or becoming branched 1–3 times below, more branched above, not (or only slightly) basally constricted below but slenderer and basally constricted above, tapering gradually to narrow apices, 1–4 cm long. Vesicles borne in axils of laterals or on upper ramuli, petiolate, subspherical, 3–6 mm in diameter, mutic or rarely with a slender mucro 2–10 mm long.

Reproduction: Thalli monoecious. Receptacles (Fig. 160A) in open racemose clusters on upper ramuli, each simple or sometimes furcate, linear-lanceolate, terete, smooth to slightly verrucose, 2–6 (–8) mm long and 0.4–1 mm broad, with scattered ostioles. Conceptacles bisexual; oogonia sessile, ovoid, 95–160 µm long and 60–105 µm in diameter, few per conceptacle; antheridia sessile or on branched paraphyses, ovoid, 16–28 pm long and 10–16 µm in diameter.

Type from "north shore of New Holland"; in BM.

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

Distribution: From Rottnest I., W. Aust., around northern Australia to Keppel Bay, Qld. New Caledonia.

In southern Australia, known from Cowell, S. Aust., drift (Womersley, 15.v.1968; ADU, A32340). N. Spencer Gulf, S. Aust., 10 m deep (Shepherd, 6.ix.1973; ADU, A44462). Wallaroo, S. Aust., drift (Harris, 24.vi.1945; ADU, A1585). Marino, S. Aust., drift ( Womersley, 18.vi.1961; ADU, A24863). Port Stanvac, S. Aust., drift (Clarke & Engler, 3.vi.1981; ADU, A53922).

Taxonomic notes: The southern Australian records of this tropical-subtropical species probably reflect a relict occurrence (as with Hormophysa triquetra) in an area with warmer summer temperatures. The Marino and Port Stanvac specimens may have drifted from western or northern Gulf St Vincent.

References:

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

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

WOMERSLEY, H.B.S. (1954b). Australian species of Sargassum, subgenus Phyllotrichia. Aust. J. Bot. 2, 337–354, Plates 1–5.

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 157A, 160A.

Figure 157   enlarge

Fig. 157. A. Sargassum decurrens (ADU, A32340). B. Sargassum heteromorphum (ADU, A42784).

Figure 160   enlarge

Fig. 160. Receptacles of species of Sargassum subgenus Phyllotrichia. A. Sargassum decurrens (ADU. A53922). B. Sargassum heteromorphum (ADU, A23954). C. Sargassum decipiens (ADU, A57476). D. Sargassum sonderi (ADU, A9314). E. Sargassum varians (ADU, A55724). F. Sargassum verruculosum (ADU. A18826).

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