Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Cystocloniaceae
Rhabdonia charoides Harvey 1862: pl. 196. J. Agardh 1876: 594. De Toni 1897: 359. Kylin 1932: 36. Lucas & Perrin 1947: 172. May 1965: 390.
Thallus (Fig. 151A) erect and spreading, soft, medium to dark red to red-brown, 5–15 cm high, much branched mainly verticillately for 4–5 orders, segments terete but narrowing to base and apex, mostly 0.5–1 (–1.5) cm long and 0.5–1 mm in diameter, shorter above, with frequent small proliferations and some branches extended into long, terminally hooked tendrils (Fig. 152D). Holdfast originally discoid, later with attachment mainly by the tendrils; epiphytic on seagrasses and larger algae. Structure uniaxial (Fig. 152A) with each axial cell producing two periaxial cells usually at right angles and alternating, developing a medulla (Fig. 152B) of elongate periaxial cells and rhizoids around the persistent axial filament, and a cortex 1–2 cells thick with slight rosettes (Fig. 151B, 152C) of small outer cells. Rhodoplasts discoid, numerous per cell.
Reproduction: Sexual thalli dioecious; procarpic. Carpogonial branches (Fig. 152E) 3-celled, borne on a cell of a periaxial filament within the cortex, orientated laterally with reflexed trichogyne. Auxiliary cell (Fig. 152F) next outwards from the supporting cell, becoming darkly staining along with adjacent cortical cells, without nutritive tissue; gonimoblast initial produced laterally or inwardly, forming a compact group of cells. Carposporophyte (Fig. 151C) with a small fusion cell, connecting back through the periaxial filament, and branched gonimoblast filaments directed mainly inwards, terminating in chains of 2–3 ovoid carposporangia 30–40 µm in diameter, surrounded by lax filamentous enveloping tissue. Cystocarps swelling branchlets, 200–300 µm across, with a slight pericarp of cortical cells, ostiolate. Spermatangia (Fig. 152G) in scattered clusters, derived via initials from outer cortical cells.
Tetrasporangia (Fig. 152H) pit-connected laterally to outer medullary cells, extending through the cortex and medulla, ovoid, 27–45 µm in diameter, zonately divided.
Type from Port Phillip Heads, Vic. (Harvey); lectotype in Herb. Harvey, TCD (Alg. Aust. Exsicc. 393E). Isolectotypes in MEL, 45110 and AD, A18254.
Selected specimens: Elliston, S. Aust., drift on Dictymenia sonderi (Womersley, 27.ii.1959; AD, A22178). Reef between Hopkins and Thistle Is, S. Aust., 7–10 m deep on Vidalia spiralis (Baldock, 1.i.1964; AD, A27117). Investigator Strait, S. Aust., 25 m deep, 35°12'S, 137°31'E (Watson, 9.i.1971; AD, A38440). Tiparra Reef, Spencer Gulf, S. Aust., 11 m deep on Posidonia sinuosa (Shepherd, 31.x.1970; AD, A37656), on Amphibolis antarctica (Shepherd, 5.xi.1970; AD, A38307) and on A. griffithii (Shepherd, 13.xii.1971; AD, A41219). Warrnambool, Vic. (Watts, Dec. 1859; MEL, 45113). Queenscliff, Vic., drift on Gelidium australe (Norris, 21.i.1963; AD, A27480). Shoreham, Westernport Bay, Vic., drift (Sinkora A1691, 16.xi.1972; AD, A53409). Wilsons Prom., Vic. (Mueller, May 1853; MEL, 45111).
Distribution: Elliston, S. Aust., to Wilsons Prom., Vic.
Taxonomic notes: Austroclonium charoides occurs in moderately deep water, epiphytic on sea-grasses and some larger algae under moderate water movement.
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
DE TONI, G.B. (1897). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 1, pp. 1–388. (Padua.)
HARVEY, W.H. (1862). Phycologia Australica. Vol. 4, Plates 181–240. (Reeve: London.)
KYLIN, H. (1932). Die Florideenordnung Gigartinales. Lunds Univ. Årsskr. N.F. Avd. 2, 28 (8), 1–88, Plates 1–28.
LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)
MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S.W. natn. Herb. 3, 349–429.
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 151 A–C, 152 A–H.
Figure 151 enlarge
Fig. 151. A–C. Austroclonium charoides (A, AD, A27117; B, AD, A27480; C, AD, A41219). A. Habit. B. Surface view of slight rosettes. C. Carposporophyte with fusion cell, chains of carposporangia, and lax filamentous involucre. D–F. Erythronaema ceramioides (D, E, AD, A8305; F, AD, A61795). D. Habit. E. Surface view of branch with rosettes. F, Section of cystocarp with erect, spreading carposporophyte with chains of carposporangia. [C as in MM-Thein & Womersley 1976.]
Figure 152 enlarge
Fig. 152. A–H. Austroclonium charoides (A–D, H, AD, A27480; E, F, AD, A41219; G, AD, A38307). A. Branch apex showing axial filament and periaxial cells. B. Transverse section of branch with axial filament, rhizoidal medulla and single-layered cortex. C. Surface view of rosettes. D. Longitudinal view of tendril branch with modified tip and lower spinous outgrowths. E. Longitudinal section of cortex with a carpogonial branch. F. Longitudinal section showing fusion of carpogonium and auxiliary cell, darkly staining cortical cells with outer cells forming the young pericarp, and young involucral filaments. G. Section of cortex with spermatangia. H. Longitudinal section of branch with tetrasporangia. I. Erythronaema ceramioides (AD, A61795). Longitudinal section of branch with tetrasporangia. [A–H after Min-Thein & Womersley 1976.]
State Herbarium of South Australia