Electronic Flora of South Australia Species Fact Sheet

Dictyota alternifida J. Agardh 1894a: 80.

Phylum Phaeophyta – Order Dictyotales – Family Dictyotaceae – Tribe Dictyoteae

Selected citations: Womersley 1967: 207.

Thallus (Fig. 65D) medium to dark brown, 5–20 cm long with branches 1–2 (–3.5) mm broad, dichotomously branched every 5–30 mm and usually with numerous, mainly marginal, proliferous laterals from the lower part of the thallus but without proliferations from the upper branches; branching relatively erect, usually with narrow axils. Holdfast rhizoidal, 1–3 mm across and with basal stolons; epilithic. Apical cells lenticular in usually broad apices, slightly hemispherical and protruding in young apices. Cortical cells (10–) 15–22 µm across, L/B 1–3 (–4). Hair tufts scattered, hairs 10–15 µm in diameter.

Thallus (Fig. 65E) olive-brown to dark brown, 5–15 cm long with branches (1–) 2–3 (–4) mm broad, becoming alternately branched close to the apices with laterals 2–10 (–20) mm apart, with rounded axils and apices; proliferations absent to occasional on lower parts. Holdfast rhizoidal, 1–6 mm across; probably epilithic. Apical cells lenticular in a broad apex, not or slightly protruding. Cortical cells (12–) 15–20 µm across, L/B 1–2 (–3). Hair tufts sparse, scattered, hairs 10–14 µ in diameter near their base.

Reproduction: Tetrasporangia (Fig. 66D,E) 50–100 µm in diameter, scattered, sparse to moderately dense. Sexual sori unknown.

Tetrasporangia (Fig. 66F) (60–) 100–160 µm in diameter, scattered singly or in small groups, sparse. Oogonial sori unknown. Antheridial sori (Fig. 66G) irregularly ovate, densely crowded, 200–600 µm long and 200–300 µm across.

Type: Type from Port Phillip Heads, Vic. (Wilson, 6.ii.1889); in Herb. Agardh, LD, 49370.

Type from Port Phillip, Vic. (Wilson, 16.xii.1887); in Herb. Agardh, LD, 49067.

Selected specimens: Head of Great Australian Bight, S. Aust., upper sublittoral (Womersley, 4.ii.1954; ADU, A19145). Coffin Bay, S. Aust., upper sublittoral just outside Kellidie Bay (Womersley, 24.ii.1959; ADU, A22562). Investigator Strait, S. Aust., 33 m deep, 35°29'S, 137°17'E (Watson, 20.i.1971; ADU, A38549). Rocky Point, Kangaroo I., S. Aust., upper sublittoral (Womersley, 23.i.1947; ADU, A4240). West I., S. Aust., 1–2 m deep (Shepherd, 14.vi.1971; ADU, A38755). Robe, S. Aust., upper sublittoral pools ( Womersley, 24.viii.1960; ADU, A2442I). Cape Northumberland, S. Aust., reef pools, uppermost sublittoral ( Womersley, 15.x.1985; ADU, A56812-"Marine Algae of southern Australia" No.254). Port Phillip, Vic., 14 m deep ( Womersley, 7.iv.1959; ADU, A22812). Wynyard, Tas., drift (Curtis, Jan. 1954; ADU, A54757; HO).


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

Distribution: From the Head of the Great Australian Bight, S. Aust. to Port Phillip Vic., and the N. coast of Tasmania.

Known from the type locality and from Portland, Vic., 8–11 m deep leeward of Lawrence Rock (Larkum, 2.ix.1971; ADU, A39637); Gabo I., Vic., 13 m deep (Shepherd, 14.ii.1973; ADU, A43324). Low Head, Tas. (Perrin 133, Oct. 1949; ADU, A47111; BM). Marion Bay, Tas., 3–5 m deep (Shepherd, 13.ii.1970; ADU, A35588, sporangial) and 10–12 m deep (Shepherd, 13.ii.1970; ADU, A35640, old male). Stapleton Point, Prosser Bay, Tas., 3–6 m deep (Shepherd, 10.ii.1970; ADU, A35730).

Taxonomic notes: This is probably the commonest species of Dictyota on southern Australian coasts, usually in the uppermost sublittoral or low eulittoral pools, often associated with sand, but known to 33 m deep. It is a relatively slender species, dichotomous above, with frequent proliferations from the lower parts.

7. Dictyota fenestrata J. Agardh 1894a: 73. Womersley 1967: 209.

Dictyota fenestrata appears to be a deeper water and infrequent species on open coasts of Victoria and Tasmania. It is distinguished by the regularly alternate laterals and the dimensions of the thallus.

References:

AGARDH, J.G. (1894a). Analecta Algologica. Cont. I. Acta Univ. lund. 29, 1–144, Plates 1, 2.

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 65D, 66D,E FIGS 65E, 66F,G.

Figure 65 image

Figure 65   enlarge

Fig. 65. A. Dictyota dichotoma (ADU, A52740). B. Dictyota dichotoma var. intricata (ADU, A10431). C. Dictyota furcellata (ADU, A8384). D. Dictyota alternifida (ADU, A56812). E. Dictyota fenestrata (ADU, A35640).

Figure 66 image

Figure 66   enlarge

Fig. 66. A–C. Dictyota furcellata (ADU, A8384). A. Apex of a branch. B. Surface view with sporangia and a hair tuft. C. Transverse section with sporangia and phaeophycean hairs. D,E. Dictyota alternifida (ADU, A56812). D. Surface view with sporangia and a hair tuft. E. Transverse section with sporangia. F,G. Dictyota fenestrata ( F, ADU, A8537; G, ADU, A35640). F. Upper branches with sporangia. G. Upper branches with male sori. H–K. Glossophora nigricans (ADU, A33254). H. Surface view with ramelli and sporangia. I. Transverse section with undivided sporangia and a ramellus. J. Surface view with ramelli and oogonial sori. K. Surface view with ramelli and male sori.

Figure 65 image

Figure 65   enlarge

Fig. 65. A. Dictyota dichotoma (ADU, A52740). B. Dictyota dichotoma var. intricata (ADU, A10431). C. Dictyota furcellata (ADU, A8384). D. Dictyota alternifida (ADU, A56812). E. Dictyota fenestrata (ADU, A35640).

Figure 66 image

Figure 66   enlarge

Fig. 66. A–C. Dictyota furcellata (ADU, A8384). A. Apex of a branch. B. Surface view with sporangia and a hair tuft. C. Transverse section with sporangia and phaeophycean hairs. D,E. Dictyota alternifida (ADU, A56812). D. Surface view with sporangia and a hair tuft. E. Transverse section with sporangia. F,G. Dictyota fenestrata ( F, ADU, A8537; G, ADU, A35640). F. Upper branches with sporangia. G. Upper branches with male sori. H–K. Glossophora nigricans (ADU, A33254). H. Surface view with ramelli and sporangia. I. Transverse section with undivided sporangia and a ramellus. J. Surface view with ramelli and oogonial sori. K. Surface view with ramelli and male sori.


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