Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Mychodeaceae
Thallus (Fig. 163F) dark red-brown, cartilaginous, 3–5 cm high, with flat main branches 3–8 mm broad bearing proliferous ramuli first from the margins and later from the broad surfaces of the frond (Fig. 165G); ramuli simple or usually branched, spiny. Holdfast crustose, 1–2 mm across; epilithic or epiphytic. Structure uniaxial with a clear apical cell and axial filament with each cell producing two periaxial filaments developing primarily in one plane, giving a flat frond (Fig. 165H) with a filamentous inner medulla, large-celled outer medulla, and a small-celled cortex, outer cells elongate-ovoid, 2–4 µm in diameter. Rhodoplasts discoid, elongate and ribbon like in inner cells.
Reproduction: Sexual thalli monoecious; procarpic; polycarpogonial. Carpogonial branches (Fig. 165I) 3-celled, 2–6 borne on enlarged inner cortical cells, auxiliary cell with gonimoblast initial radiating laterally and inwardly, producing clusters of ovoid carposporangia 10–15 µm in diameter within the filamentous matrix. Cystocarps (Fig. 163G) within the spinous ramuli, swollen, 0.6–1 mm in diameter, with slight enveloping tissue and the cortex breaking down for release of carpospores. Spermatangial clusters (Fig. 165J) scattered in the outer cortex of the ramuli, sunken, with 4–5 initials each producing two elongate-ovoid spermatangia 2–3 µm in diameter.
Tetrasporangia (Fig. 165K) scattered in the outer cortex, laterally attached, ovoid, 25–35 µm long and 14–18 µm in diameter, zonately divided.
Type from Cape Lannes, S. Aust. (Kraft, 10.ii.1973); holotype in AD, A44728, with isotypes.
Selected specimens: Pennington Bay, Kangaroo I., S. Aust., sublittoral fringe (Kraft, 3.xii.1971; AD, A44727). Margaret Brock Reef, Cape Jaffa, S. Aust., 4–5 m deep in caves (R. Lewis, 29.xi.1972; AD, A42924). Lawrence Rock, Vic., in low pools (Beauglehole, 15.i.1960; AD, A24742). Koonya, Vic. (Lukey, Jan. 1954; AD, A23247). Shack Bay, Inverloch, Vic., 4 m deep (O'Brien, 24.i.1976; MELU, 23159). Dover, Tas., 4–6 m deep under Macrocystis (Sanderson & Kraft, 8.iv.1988; MELU, K7842).
Distribution: Pennington Bay, Kangaroo I., S. Aust., to Inverloch, Vic., and SE Tasmania. Jervis Bay, N.S.W. (Millar & Kraft 1993, p. 22).
Taxonomic notes: M. acanthymenia is characterised by the flat thalli bearing spinous ramuli, the prominent central axis, and cystocarps borne in the base of the ramuli. It is known mainly from uppermost sublittoral rock on rough-water coasts.
KRAFT, G.T. (1978). Studies of marine algae in the lesser-known families of the Gigartinales (Rhodophyta). III. The Mychodeaceae and Mychodeophyllaceae. Aust. J. Bot. 26, 515–610.
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.
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 163F, G, 165 G–K.
Figure 163 enlarge
Fig. 163. A. Mychodea spinulifera (AD, A34186). Habit, on Amphibolis. B, C. Mychodea aciculare (B, AD, A44712; C, AD, A44711). B. Habit. C. Cross section of cystocarp with emergence of the hydrozoan on the right. D, E. Mychodea pusilla (D, lectotype in TCD; E, AD, A44703). D. Habit. E. Habit of a cystocarpic plant. F, G. Mychodea acanthymenia (AD, A44728). F. Habit of holotype. G. Section of a mature cystocarp. [D–G as in Kraft 1978.]
Figure 165 enlarge
Fig. 165. A–F. Mychodea pusilla (AD, A44705). A. Branches with cystocarps. B. Transverse section of a branch with tetrasporangia. C. Section of cortex with polycarpogonial supporting cells. D. Section of cortex with an auxiliary cell producing gonimoblast initials. E. Section of cortex with a sunken spermatangial cluster. F. Section of cortex with tetrasporangia. G–K. Mychodea acanthymenia (AD, A44728). G. Upper branches with spinous ramuli (cystocarpic on left). H. Transverse section of branch. I. Section of cortex with polycarpogonial supporting cells. J. Section of cortex with sunken spermatangial clusters. K. Longitudinal section of thallus with tetrasporangia. [A–K after Kraft 1978.]
State Herbarium of South Australia