Electronic Flora of South Australia Species Fact Sheet

Sargassum heteromorphum J. Agardh 1872: 60; 1889: 42, pl. 1.

Phylum Phaeophyta – Order Fucales – Family Sargassaceae

Selected citations: Lucas 1936: 63 fig. 40. Womersley 1954b: 345, fig. 1c, pl. 2 fig. 2.

Synonym

Sargassum halitrichum J. Agardh 1889: 43, pl. 13.

Reproduction: Thalli monoecious. Receptacles (Fig. 160B) in racemose clusters on upper ramuli, sessile or pedicellate, terete to lanceolate, verrucose, simple or with short lateral branches, 1.5–3 (–4) mm long and 0.3–1.2 mm in diameter, with scattered ostioles. Conceptacles unisexual or bisexual; oogonia sessile, ovoid, 200–350 long and 150–250 in diameter, few per conceptacle; antheridia sessile or on branched paraphyses, ovoid, 16–28 µm long and 10–14 µm in diameter.

Type from Georgetown, Tas. (Gunn); in Herb. Agardh, LD, 2626.

Selected specimens: Eucla, W. Aust., drift ( Womersley, 5.x.1979; ADU, A50634). St Francis I., Isles of St Francis, S. Aust., 6 m deep (Shepherd, 8.i.1971; ADU, A37926). Tiparra reef, S. Aust., 10 m deep (Shepherd, 18.x.1972; ADU, A42784). Barker Rocks, Yorke Pen., S. Aust., drift (Womersley, 24.ix.1967; ADU, A31959). Port Willunga, S. Aust., drift (Womersley, 25.x.1959; ADU, A23954). Rocky Point Beach, Kangaroo I., S. Aust., drift (Womersley, 26.viii.1950; ADU, A13319). Dutton Beach, Portland, Vic., drift (Beauglehole, 14.vii.1951; ADU, A21799). St Leonards, Port Phillip, Vic., 1–3 m deep ( Womersley, 9.viii.1959; ADU, A23089). San Remo, Vic., drift (Levring, 7.vi.1948; ADU, A56166).

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

Distribution: From Rottnest I., W. Aust., around southern Australia to San Remo, Vic., and the north coast of Tasmania.

Taxonomic notes: 7'hallus (Fig. 157B) dark brown, 10–45 cm long, with a stipe 0.5–2 cm long, terete with stubby branch residues, 1–3 mm in diameter, bearing apically one to several primary laterals.

Holdfast discoid-conical, becoming lacerate, 5–15 mm across, with one (–3) stipes; epilithic. Primary branches 10–40 cm long, subdistichous, pinnate to bipinnate and complanately branched below with axes 5–10 mm broad, 3–10 mm between branchings; upper parts irregularly and not complanately branched. Laterals alternately pinnate, 2–5 cm long below with segments 3–6 (–9) mm broad, more or less linear with rounded apices or tapering to narrow apices, axils mostly rounded; upper laterals (on fertile fronds) markedly narrower, becoming filiform, terete to compressed, irregularly branched, usually 2–5 cm long and 200–500 (–800) µm broad. Vesicles borne on upper ramuli, petiolate, subspherical, 1–2 (–3) mm in diameter, with a short, acute, apical mucro.

Sargassum heteromorphum is present in most collections only as basal parts, but fertile fronds commence in May and are fully developed in October to December, after which they are lost. It differs from S. decurrens in the relatively sudden transition to filiform upper laterals, the smaller vesicles, and shorter receptacles bearing short, sterile, lateral branches.

The record of Basson (1979, p. 60, fig. 33) from the Arabian Gulf is more likely of S. decurrens.

References:

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.

BASSON, P.W. (1979). Marine algae of the Arabian Gulf coast of Saudi Arabia (first half). Bot. Mar. 22, 47–64.

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

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

Illustration in Womersley Part II, 1997: FIGS 157B, 16013.

Figure 157   enlarge

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

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