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Audouinella microscopica (Nägeli in Kützing)Woelkerling 1971: 33, figs 10, 23A; 1972: 85, figs 1–14; 1973b: 557, figs 46–51.

Phylum Rhodophyta – Class Florideophyceae – Order Acrochaetiales – Family Acrochaetiaceae

Selected citations: Garbary 1979b: 479; 1987: 116. Garbary et al. 1983: 35, fig. 14. Millar & Kraft 1993: 7.


Callithamnion microscopicum Nägeli in Kützing 1849: 640.

Acrochaetium microscopicum (Nägeli) Nägeli 1861: 407. Lee 1987: 30, fig. 14.

Acrochaetium catenulatum Howe 1914: 84, pl. 31 figs 12–18. Levring 1953: 472, fig. 8.

Thallus (Fig. 12G–M) epiphytic, 30–125 µm high exclusive of hairs; original spore persisting as a unicellular base slightly smaller to slightly larger than other cells, rarely dividing to form a several-celled prostrate system. Erect filaments (Fig. 12G–M) 1–3 (–4), commonly curved, mostly 20–100 µm long, simple or with a few secundly to irregularly arranged laterals. Cells (Fig. 12G–M) barrel-shaped to cylindrical, 3–12 µm in diameter and 3–10 µm long, with smaller cells near the apices, L/D 0.7–1.5 (–2), each cell containing a single parietal laminate to stellate rhodoplast (Fig. 12L) with one pyrenoid. Terminal and pseudolateral hairs up to 100 µm long occur.

Reproduction: Monosporangia (Fig. 12G–M) ovoid, 4–7 µm in diameter and 5–10 µm long, terminal or lateral, single or rarely in pairs, sessile or stalked, adaxially senate or occasionally more scattered.

Other reproductive structures unknown in southern Australian collections (see Stegenga & Mulder 1979).

Type from Torquay, England (see Woelkerling 1972, p. 86); holotype in L, 940, 285 ... 306.

Selected specimens: Radar Reef, Rottnest I., W. Aust., on Polysiphonia sp. on Codium laminarioides, 10 m deep (Woelkerling, 11.xi.1968; AD, A32931). Port Elliot, S. Aust., on Sphacelaria tribuloides, upper sublittoral (Parsons, 31.i.1968; AD, A32271 -"Marine Algae of southern Australia" No. 64a) and on Sphacelaria brachygonia, lower eulittoral (Woelkerling, 1.iii.1968; AD, A32250 -"Marine Algae of southern Australia" No. 64b). Port MacDonnell, S. Aust., on A. caespitosa on Codium pomoides, reef pools (Womersley, 25.i.1967; AD, A32113). Burraneer, N.S.W., on Cladophora (Levring, 16.xi.1947; AD, A19855).

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

Distribution: Cosmopolitan, on various algae.

In southern Australia, from Rottnest I., W. Aust., to Port MacDonnell, S. Aust., and to Coffs Harbour, N.S.W.

Taxonomic notes: Audouinella microscopica is a small but distinctive species, separated from other audouinelloid algae in southern Australia by its unicellular holdfast, barrel shaped cells, and commonly arcuate filaments less than 125 µm long. Up to four erect filaments may arise from the basal cell of each plant, and when only one develops, the lowermost lateral may arise from any cell above the base. Irregularly lobate rhodoplasts occur in cells of southern Australian plants; Hamel (1928b, p. 110) and Levring (1953, p. 472), however, recorded stellate rhodoplasts in this species.

Stegenga & Mulder (1979) have discussed the "A. microscopica" complex on the basis of culture studies and consider that genotypic differences exist with sexual life histories present in some. Only monosporangial plants are known from southern Australia, and until culture studies are carried out it seems best to use the name microscopica for this complex, as do Schneider (1983, p. 13) and Garbary et al. (1983, p. 36).


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.

GARBARY, D.J., HANSEN, G.I. & SCAGEL, R.F. (1983). The marine algae of British Columbia and northern Washington: Division Rhodophyta (red algae), Class Florideophyceae, Orders Acrochaetiales and Nemaliales. Syesis 15 (suppl.), 1–102.

HAMEL, G. (1928b). Floridées de France V. Acrochaetium Naegeli; Rhodochorton Naegeli. Rev. Algol. 3, 99–158.

HOWE, M.A. (1914). The marine algae of Peru. Mem. Torrey Bot. Club 15, 1–185, Plates 1–66.

KÜTZING, F.T. (1849). Species Algarum. (Leipzig.)

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

LEVRING, T. (1953). The marine algae of Australia. I. Rhodophyta: Goniotrichales, Bangiales and Némalionales. Arkiv för Bot. Ser. 2, 2, 457–530.

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.

NÄGELI, C. (1861). Beitrage zur Morphologie and Systematik des Ceramiaceae. Sber. bayer. Akad. Wiss. Jb., 1861, 1, 297–415, Plate 1.

SCHNEIDER, C.W. (1983). The red algal genus Audouinella Bory (Nemaliales: Acrochaetiaceae) from North Carolina. Smithsonian Contr. Mar. Sci. No. 22, pp. 1–25.

STEGENGA, H. & MULDER, A.S. (1979). Remarks on the Audouinella microscopica (Nag.)Woelkerling complex, with a brief survey of the genus Chromastrum Papenfuss (Rhodophyta, Nemaliales). Acta Bot. Neerl. 28, 289–311.

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

WOELKERLING, W.J. (1972). Studies on the Audouinella microscopica (Naeg.)Woelk. complex (Rhodophyta). Rhodora 74, 85–96.

WOELKERLING, W.J. (1973b). The morphology and systematics of the Audouinella complex (Acrochaetiaceae, Rhodophyta) in northeastern United States. Rhodora 75, 529–621.

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. 12 G–M.

Figure 12 image

Figure 12   enlarge

Fig. 12. A–F. Audouinella unifila (A, E, AD, A32110; B–D, F, AD, A31373; all shown on host cells). A. Sporelings. B. Thallus with monosporangia and spermatangia. C. Mature thallus coiled around host. D. Mature erect thallus with monosporangia; three cells shown with rhodoplasts, one with a pyrenoid. E. Thallus with four carpogonia; two cells shown with rhodoplasts. F. Thallus with a carposporophyte. G–M. Audouinella microscopica (G–L, AD, A32250; M, AD, A19855). G–K. Thalli with monosporangia, showing variation within a single population. L. Thallus with hairs, monosporangia, and four cells shown each with a rhodoplast and pyrenoid. M. Mature thallus with denser branching. [A–I, K–M after Woelkerling 1971.]

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