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Electronic Flora of South Australia Species Fact Sheet

Audouinella floridula (Dillwyn) Woelkerling 1971: 30, figs 8, 23B.

Phylum Rhodophyta – Class Florideophyceae – Order Acrochaetiales – Family Acrochaetiaceae

Selected citations: Dixon & Irvine 1977b: 97, fig. 27. Garbary 1987: 73.


Conferva floridula Dillwyn 1802–1809: 73.

Rhodochorton floridulum (Dillwyn) Nägeli. Knaggs 1965: 478, figs 1–4. Stegenga 1978: 281, figs 13–27.

Rhodothamniella floridula (Dillwyn) Feldmann in Christensen 1978: 67. Stegenga 1985: 326, fig. 25.

Thallus (Fig. 7A) medium to dark red, epilithic, caespitose to matted, (3–) 10–20 (–25) mm high; original spore non-persistent. Prostrate system (Fig. 7B) consisting of branched discrete entangled and stoloniferous filaments. Erect filaments (Fig. 7A, B) unbranched to sparingly branched below, sparingly to moderately branched above; laterals secundly to irregularly arranged and sometimes tapering towards the tips. Cells (Fig. 7C, D) cylindrical, 15–30 µm in diameter and (35–) 50–120 (–150) µm long, L/D 2–5 (–6), tapering to 14–19 µm in diameter near the apices; cells of shorter laterals 8–12 µm in diameter, 12–36 µm long; all cells containing several (usually 3–10) parietal, more or less stellate rhodoplasts (Fig. 7D) each with a single pyrenoid.

Reproduction: Tetrasporangia (Fig. 7C) ovoid to globose, 18–30 (–40) µm in diameter and (20–) 25–40 (–45) µm long, sessile or on 1–3-celled stalks, mostly arranged in adaxial secund series along the laterals, cruciately divided.

Other reproductive bodies unknown in southern Australian collections. Stegenga (1978) reports minute dioecious gametophytes and direct formation of a tetrasporophyte from the fertilized carpogonium, without a carposporophyte.

Type from the Galway coast, Ireland; lectotype in BM (see Dixon & Irvine 1977b, p. 97).

Selected specimens: Christies Beach, S. Aust., in sandy pools (Womersley, 14.x.1968; AD, A32869). Robe, S. Aust., lower eulittoral on rock (Womersley, 24.viii.1960; AD, A24423), The Blowholes, Cape Bridgewater, Vic. (Womersley, 21.viii.1953; AD, A19057). Western Port, Vic. (Harvey, Alg. Aust. Exsicc, 518, 1854; AD, A18476). Taylors Point, Sydney, N.S.W. (V. Genes, 22.x.1950; AD, A17289).

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

Distribution: Widely distributed in most temperate seas.

In southern Australia, from Christies Beach, S. Aust., to Western Port, Vic., and Taylors Point, Sydney, N.S.W.

Taxonomic notes: Audouinella floridula is easily distinguished from other species in the complex (even when sterile) by its relatively large cells with numerous, stellate rhodoplasts, each with a central pyrenoid. It usually grows on sand-covered rock.


CHRISTENSEN, T. (1978). Annotations to a textbook of phycology. Bot. Tidsskr. 73, 65–70.

DILLWYN, L.W. (1802–1809). British Confervae. (Phillips: London.)

DIXON, P.S. & IRVINE, L.M. (1977b). Seaweeds of the British Isles. Vol. 1, Rhodophyta. Part I, Introduction, Nemaliales, Gigartinales. [British Museum (N.H.): London.]

GARBARY, D.J. (1987). The Acrochaetiaceae (Rhodophyta): An annotated bibliography. Bibl. Phycol. 77, 1–267.

KNAGGS, F.W. (1965). Contributions to the life-history of Rhodochorton floridulum (Dillw.)Nag. Br. phycol. Bull. 2, 478–485.

STEGENGA, H. (1978). The life histories of Rhodochorton purpureum and Rhodochorton floridulum (Rhodophyta, Nemaliales) in culture. Br. phycol. J. 13, 279–289.

STEGENGA, H. (1985). The marine Acrochaetiaceae (Rhodophyta) of southern Africa. S. Afr. J. Bot. 51, 291–330.

WOELKERLING, W.J. (1971). Morphology and taxonomy of the Audouinella complex (Rhodophyta) in southern Australia. Aust. J. Bot. Suppl. 1, 1–91.

The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.

Author: W.J. Woelkerling & H.B.S. Womersley

Publication: Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1994: FIG. 7 A–D.

Figure 7 image

Figure 7   enlarge

Fig. 7. A–D. Audouinella floridula* (A, B, D, AD, A24423; C, AD, A19057). A. Branching pattern. B. Prostrate system and erect filaments, with young sporangia (numerous cells omitted at broken lines). C. Upper filament with young and mature tetrasporangia. D. Mature cells with rhodoplasts with pyrenoids. E–H. Audouinella saviana (E–G, AD, A33398; H, AD, A32291). E. Branching pattern, with prostrate system and monosporangia on upper branches. F. Upper branches with monosporangia. G. Cells with rhodoplasts and a monosporangium. H. Tetrasporangia.

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