Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Acrochaetiales – Family Acrochaetiaceae
Selected citations: Garbary 1987: 154.
Acrochaetium repens Boergesen 1915: 52, figs 55, 56; 1920: 452, fig. 420. Garbary 1979b: 479.
Thallus (Fig. 15H) largely endophytic, developing from aseptate spores sometimes persisting in mature plants. Prostrate system (Fig. 15H) consisting of sparingly and irregularly branched discrete filaments creeping within the host. Cells irregular to cylindrical in shape, commonly broadest in the middle, 6–12 (–20) µm in diameter and 18–40 µm long, L/D (1–) 2–4 (–5), each cell containing a parietal lobate to stellate rhodoplast with one pyrenoid. Erect filaments (Fig. 1511, L) arising at irregular intervals from cells of the prostrate system, simple or sparingly branched, 200–800 µm high. Cells (Fig. 15L) cylindrical, 5–7 (–9) µm in diameter and 10–25 µm long (L/D 2–4) in lower portions, 4–7 µm in diameter and 30–80 µm long (L/D 4–20) in upper portions, occasionally tapering to 2 µm in diameter and L/D up to 30 near the apices; lower cells with a parietal lobate to stellate rhodoplast (Fig. 15L) and one pyrenoid; upper cells usually with slightly developed rhodoplasts or none.
Reproduction: Monosporangia (Fig. 15I) ovoid, 8–11 µm in diameter and 12–19 µm long, sessile or stalked, single or in pairs, scattered on the erect and occasionally on the prostrate filaments.
Thalli apparently dioecious. Carpogonia (Fig. 15J) sessile or stalked, on prostrate or occasionally on erect filaments, dividing transversely after fertilization and producing carposporangia directly or forming short gonimoblast filaments with clusters of terminal ovoid carposporangia (Fig. 15K) 8–11 µm in diameter and 14–20 µm long. Spermatangia (Fig. 15L) ovoid, 2–4 µm in diameter and 4–6 µm long, solitary or in groups of 2–3, sessile on vegetative cells or on 1–2-celled stalks, terminal or lateral on erect filaments.
Type from the harbour, St Thomas, Virgin Is, on Hypnea musciformis; holotype in C.
Selected specimens: Point Sinclair, S. Aust., in Leptosomia(?), drift (Oberlander, 11.i.1961; AD, A24701). Victor Harbor, S. Aust., in Naccaria naccarioides, drift (Abbott, 2.xi.1965; AD, A32256). Taroona, Tas., in N. naccarioides, 3–6 m deep (Shepherd, 4.ii.1970; AD, A59564).
Distribution: N. Atlantic.
In southern Australia, from Point Sinclair and Victor Harbor, S. Aust., and Taroona, Tasmania.
Taxonomic notes: Audouinella repens is readily distinguished from other known southern Australian audouinelloid algae by the presence of progressively longer cells towards the apices of the erect filaments. In addition to lacking this feature, Audouinella saviana and A. secundata, which also have main axes 10 µm or less in diameter, differ in being epiphytic and not endophytic and in having somewhat larger monosporangia.
BOERGESEN, F. (1915). The marine algae of the Danish West Indies. Part 3. Rhodophyceae. Dansk bot. Ark. 3, 1–80.
BOERGESEN, F. (1920). The marine algae of the Danish West Indies. Part 3. Rhodophyceae. Dansk bot. Ark. 3, 369–504.
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.
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.
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. 15 H–L.
Figure 15 enlarge
Fig. 15. A–G. Audouinella barbadensis (AD, A30880). A. Branching pattern. B. Prostrate system and erect filaments. C. Cells of an erect filament each with a rhodoplast and pyrenoid. D. Branches with monosporangia. E. Branches with an inflated cell and a carpogonium. F. Branch with a mature carposporophyte. G. Branches with spermatangia. H–L. Audouinella repens (H, AD, A24701; I–L, AD, A32256). H. Branching pattern of thallus in Leptosomia(?) I. Branch with monosporangia. J. Fertilized carpogonium following division. K. Two young carposporophytes on opposite sides of an erect filament. L. Erect filaments with spermatangia, a carpogonium and cells of prostrate system each with a rhodoplast and pyrenoid. [A, C–G, I–L after Woelkerling 1971.]
State Herbarium of South Australia