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Audouinella dictyotae (Collins) Woelkerling 1971: 38, figs 13,25.

Phylum Rhodophyta – Class Florideophyceae – Order Acrochaetiales – Family Acrochaetiaceae

Selected citations: Garbary 1979b: 478; 1987: 60. Lee 1987: 12, figs 4,5. Millar & Kraft 1993: 7.


Acrochaetium dictyotae Collins 1906: 193.

Rhodochorton dictyotae (Collins) Drew 1928: 190, pl. 47 figs 79,80.

Thallus (Fig. 10A) medium red to grey-red, almost entirely epiphytic, caespitose, usually 2–4 mm high; original spore non-persistent. Prostrate system (Fig. 10B) consisting of a more or less discoid mass of branched filaments with large single cells or short filaments penetrating the host tissue or occasionally without a superficial disc. Erect filaments (Fig. 10A) irregularly to secundly branched and gradually tapering towards the apices. Cells (Fig. 10C, D) cylindrical, (10–) 12–15 (–18) µm in diameter and (24–) 35–60 (–90) µm long (L/D 1.5–5) in lower portions of main axes, 10–12 µm in diameter and 30–80 µm long (L/D 3–8) in laterals, tapering to 6–9 µm in diameter near the apices; each cell containing a parietal lobate rhodoplast (Fig. 10D) (sometimes subdivided into 2–4) and 1–4 pyrenoids. Hairs unknown.

Reproduction: Monosporangia (Fig. 10C, D) ovoid to subglobose, (10–) 12–17 µm in diameter and 16–24 pin long, sessile and solitary or occasionally 1–2 together on unicellular stalks, situated mainly on the lowermost cells of lateral branches; occasionally replaced by bisporangia (Fig. 10E) 12–16 µm in diameter and 14–22 µm long.

Thallus monoecious. Carpogonia (Fig. 10F) sessile or stalked, solitary or occasionally in groups of 2–3; stalk cells sometimes producing a sterile filament prior to or after fertilization; fertilized carpogonium either dividing transversely or remaining undivided prior to gonimoblast formation; gonimoblast filaments short or absent; mature carposporangia (Fig. 10G) globose and thick-walled, 18–30 µm in diameter, usually 3–10 per carposporophyte. Spermatangia (Fig. 10H) spherical to ovoid, 3–5 µm in diameter and 4–6 µm long, borne in small clusters on branched stalks or in groups of 1–3 on 1–2-celled stalks,

Tetrasporangia unknown.

Type from La Jolla California; holotype in FH. Material from the type collection has been distributed in Phycotheca Boreali Americana, No. 1394.

Selected specimens: Port Noarlunga, S. Aust., uppermost sublittoral on shore reef, on Dictyota (Womersley, 12.x.1991; AD, A61495 -"Marine Algae of southern Australia" No. 358). Aldinga, S. Aust., on Dictyota diemensis, upper sublittoral pools (Womersley, 25.x.1964; AD, A28372 and 11.x.1965; AD, A29615). Amphitheatre Rock, West I., S. Aust., 13–20 m deep, on Glossophora nigricans (Shepherd, 1.i.1969; AD, A33259). Seal Bay, Kangaroo I., S. Aust., on Dictyota diemensis, drift (Womersley, 22.xi.1968; AD, A32971). Port MacDonnell, S. Aust. on D. diemensis, upper sublittoral pools (Womersley, 25.i.1967; AD, A31667). Lawrence Rock, Portland, Vic., on D. diemensis in pools (Beauglehole, 13.i.1954; AD, A20551).

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

Distribution: San Diego County, California; Korea.

In southern Australia, from Port Noarlunga, S. Aust., to Portland, Vic., on Dictyota (mainly D. diemensis) and Glossophora nigricans. Twofold Bay, N.S.W.

Taxonomic notes: Thalli in southern Australian collections of Audouinella dictyotae are larger and more robust but otherwise agree with holotype material from California. Bisporangia occurred in small numbers on sexual plants in one collection (AD, A31667).

Guiry et al. (1987) and Bidoux & Magne (1989) found that cells of A. caespitosa possess several separate rhodoplasts each with a pyrenoid, rather than a single rhodoplast, and the plastid situation in A. dictyotae should be checked.

Carposporophyte-bearing plants of Audouinella dictyotae are readily distinguished from those of A. caespitosa, but non-sexual plants of the two species are occasionally very similar and could be confused. However, A. dictyotae seldom exceeds 3 mm in height, may have secund branching, lacks multicellular hair-like prolongations, has cells which rarely exceed 15 µm in diameter, and has monosporangia under 25 µm long that are often sessile. A. caespitosa, in contrast, often reaches 4–6 mm in height, has irregularly branched erect filaments which sometimes end in hair-like prolongations, has erect filaments which frequently exceed 15 µm in diameter, and has mostly stalked monosporangia usually longer than in A. dictyotae.


BIDOUX, C. & MAGNE, F. (1989). Étude de quelques Acrochaetiales (Rhodophyta) devant étre rapportées au genre Rhodothamniella. Cryptogamie, Algol. 10, 33–55.

COLLINS, F.S. (1906). Acrochaetium and Chantransia in North America. Rhodora 8, 189–196.

DREW, K.M. (1928). A revision of the genera Chantransia, Rhodochorton, and Acrochaetium with descriptions of the marine species of Rhodochorton (Naeg.) gen. emend. on the Pacific Coast of North America. Univ. Calif. Pubis Bot. 14, 139–224, Plates 37–48.

GARBARY, D.J. (1979b). Numerical Taxonomy and generic circumscription in the Acrochaetiaceae (Rhodophyta). Bot. Mar. 22, 477–492.

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

GUIRY, M.D. KEE, W.R. & GARBARY, D.J. (1987). Morphology, temperature and photoperiodic responses in Audouinella botryocarpa (Harvey)Woelkerling (Acrochaetiaceae, Rhodophyta) from Ireland. Glom. Bot. Ital. 121, 229–246.

LEE, Y.P. (1987). Taxonomy of the Rhodochortonaceae (Rhodophyta) in Korea. Korean J. Phycol. 2, 1–50.

MILLAR, A.J.K. & KRAFT, G.T. (1993). Catalogue of Marine and Freshwater Red Algae (Rhodophyta) of New South Wales, including Lord Howe Island, South-western Pacific. Aust. Syst. Bot. 6, 1–90.

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. 10 A–H.

Figure 10 image

Figure 10   enlarge

Fig. 10. A–H. Audouinella dictyotae (A, B, E–H, AD, A28372; C, D, AD, A31667). A. Branching pattern, with prostrate system, erect branches and clusters of carposporangia. B. Prostrate system shown in sectional view on Dictyota thallus. C. Branches with monosporangia. D. Branch with monosporangia and cells with rhodoplasts with one to four pyrenoids. E. Branch with bisporangia. F. Branches with carpogonia on stalk cells. G. Mature carposporophyte. H. Branch with spermatangia. I-0. Audouinella caespitosa (I, J, AD, A32283; K–N, AD, A30878; 0, AD, A19795). I. Branching pattern with prostrate system of plant on Codium. J. Erect branches with monosporangia and rhodoplasts each with a pyrenoid shown in some cells. K. Mature carpogonium. L. Young carposporophyte. M. Mature carposporophyte. N. Branch with spermatangia. 0. Branch with tetrasporangia. [B–H after Woelkerling 1971; K-0 after Woelkerling 1970.]

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