Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Areschougiaceae
Areschougia (?) dumosa Harvey 1863: pl. 282. J. Agardh 1876: 281; 1894: 127; 1897: 40. Ky lin 1932: 37.
Stenocladia ramulosa J. Agardh 1892: 101. Lucas & Perrin 1947: 181.
Thallus (Fig. 117D) dark brown-red, drying almost black, cartilaginous, 5–10 cm high, much branched radially and irregularly, with main branches 0.7–1.5 (–2) mm in diameter bearing distinctly slenderer laterals (150–) 200–250 µm in diameter. Holdfast discoid, 4–8 mm across; epilithic. Structure (Fig. 119G) uniaxial, with each axial cell cutting off a single periaxial more or less on three radii, producing a lax medulla of periaxial filaments, becoming filled with rhizoids in older branches, splaying out and merging to a pseudoparenchymatous cortex 3–7 cells thick, inner cells elongate and 4–6 µm in diameter, outer cells 2–3 µm in diameter, L/D (2–) 3–5. Rhodoplasts discoid, few per cell.
Reproduction: Sexual thalli monoecious; procarpic. Carpogonial branches (Fig. 119H) 3-celled, borne on outer medullary cells, lying more or less parallel to the supporting cell with a relatively straight trichogyne, and sometimes with 1–2 sterile cells on the basal cell. Auxiliary cell immediately above the supporting cell, becoming enlarged and more darkly staining; connecting filaments not seen; cells adjacent to auxiliary cell producing small darkly staining nutritive cells. Gonimoblast initials inwards to lateral, later radial from the branched fusion cell (with its stalk from the periaxial filament), with short chains of ovoid carposporangia (Fig. 119I) 10–15 µm in diameter. Cystocarp (Fig. 117E) without filamentous enveloping tissue, swelling the branch, 400–600 µm across, ostiolate. Spermatangia scattered in small groups near branch ends, with surface cortical cells cutting off 3–5 initials each producing 2–3 ovoid spermatangia, 2–3 µm in diameter.
Tetrasporangia (Fig. 119J) scattered over young branches, pit-connected to an inner cortical cell, ovoid, 24–36 µm long and 10–16 µm in diameter, zonately divided.
Type from Warrnambool, Vic. (Watts 122, March 1860); holotype in Herb. Harvey, TCD.
Selected specimens: Lands End, West I., S. Aust., 16–20 m deep (Shepherd, 2.i.1967; AD, A31616). Oedipus Point, West I., S. Aust., 16 m deep (Shepherd, Dec., 1966; AD, A31150). Robe, S. Aust., deep shaded pool, outer coast (Womersley, 27.viii.1949; AD, A11068). Nora Creina, S. Aust., reef pools (Womersley, 26.i.1967; AD, A31646). 1.3 km off Cape Northumberland, S. Aust., 15 m deep (Shepherd, 21.vi.1976; AD, A55172). Port MacDonnell, S. Aust., drift (Womersley, 15.iv.1959; AD, A22996). Little Beach, Discovery Bay, Vic., drift (Beauglehole 156, 14.i.1950; AD, A15609). Queenscliff, Vic., drift (Womersley, 8.iv.1959; AD, A22839). Bicheno, Tas., 17 in deep (McCauley, 26.ii.1990; AD, A60421).
Distribution: West I., S. Aust., to Queenscliff, Vic., and SE Tasmania.
Taxonomic notes: Melanema dumosum is distinctive in habit and occurs from shaded pools to 20 m deep.
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
AGARDH, J.G. (1892). Analecta Algologica. Acta Univ. lund. 28, 1–182, Plates 1–3.
AGARDH, J.G. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.
AGARDH, J.G. (1897). Analecta Algologica. Cont. IV. Acta Univ. lund. 33, 1–106, Plates 1, 2.
HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)
LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)
MIN-THEIN, U. & WOMERSLEY, H.B.S. (1976). Studies on southern Australian taxa of Solieriaceae, Rhabdoniaceae and Rhodophyllidaceae (Rhodophyta). Aust. J. Bot. 24, 1–166.
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.
Illustrations in Womersley Part IIIA, 1994: FIGS 117D, E, 119 G–J.
Figure 117 enlarge
Fig. 117. A. Areschougia congesta (AD, A52195). Habit. B. Areschougia ligulata (AD, A42421). Habit. C. Areschougia stuartii (AD, A42234). Habit. D, E. Melanema dumosum (D, AD, A31150; E, AD, A22996). D. Habit. E. Longitudinal section of a cystocarp. [B as in Min-Theis & Womersley 1976.]
Figure 119 enlarge
Fig. 119. A–E. Areschougia stuartii (A, AD, A33002; B, C, AD, A18256; D, AD, A585; E, AD, A61355). A. Longitudinal section with axial filament, medulla and cortex. B. Section of cortex with a carpogonial branch with 3 sterile cells on the basal cell. C. Longitudinal section showing carposporophyte with fusion cell and chains of carposporangia. D. Section of cortex with a tetrasporangium. E. Section of outer cortex with paraphyses and spermatangia. F. Areschougia congesta (AD, A56532). Section of outer cortex with paraphyses and spermatangia. G–J. Melanema dumosum (G–I, AD, A31646; J, AD, A11068). G. Longitudinal section showing axial filament, medulla and cortex. H. Longitudinal section with 3 carpogonial branches. I. Longitudinal section of branch and carposporophyte with fusion cell and chains of carposporangia, and ostiole. J. Section of cortex with immature and mature tetrasporangia. [A–D, G–J after Min-Thein & Womersley 1976.]
State Herbarium of South Australia