Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Mychodeaceae
Selected citations: Kraft 1978: 560, figs 20, 41A, B. Kylin 1932: 65, pl. 27 fig. 67.
Thallus (Fig. 163A) dark red-brown, 4–6 cm high, with subdichotomous, terete to slightly compressed axes 1–2 (–3) mm broad, more or less densely covered throughout with simple, acute, spinous ramuli (Fig. 164A). Holdfast crustose, 2–4 mm across; epiphytic on Amphibolis. Structure uniaxial, with a prominent apical cell and axial filament in upper parts, obscured below, with each axial cell producing two periaxial filaments and numerous cross-connector cells; inner medulla of slender filaments, outer medulla of large cells (with few filaments) and a cortex of anticlinal filaments, outer cells ovoid, 2–4 µm in diameter. Rhodoplasts discoid to elongate.
Reproduction: Sexual thalli monoecious; procarpic; polycarpogonial. Carpogonial branches (Fig. 164B) 3-celled, borne on enlarged inner cortical cells in the swollen bases of spinous ramuli, with the auxiliary cell producing several gonimoblast initials towards the centre of the axis; cystocarps unknown. Spermatangial clusters (Fig. 164C) scattered, sunken in the cortex of ramuli and main axes, with initials producing 2–3 ovoid spermatangia 2–3 in diameter.
Tetrasporangia (Fig. 164D) scattered in the outer cortex, laterally attached, ovoid, 40–48 µm long and 28–32 [im in diameter, zonately divided.
Type from Fowlers Bay, S. Aust. (O'Halloran, 1894); holotype in Herb. Agardh, LD, 34058.
Selected specimens: (all on Amphibolis): Eucla, W. Aust., drift (Kerry, Sept. 1975; MELU, 23680). Head of Great Australian Bight, S. Aust., upper sublittoral (Womersley, 4.ii.1954; AD, A19158); drift (Gordon, 4.xi.1968; AD, A34189 and Parsons, 4.xi.1968; AD, A34186).
Distribution: Eucla, W. Aust., to Fowlers Bay, S. Aust.
Taxonomic notes: This little known species appears to be of restricted distribution, only known on Amphibolis. It is characterised by the terete to slightly compressed, subdichotomous axes which are covered on all sides by short, acute, spines.
AGARDH, J.G. (1897). Analecta Algologica. Cont. IV. Acta Univ. lund. 33, 1–106, Plates 1, 2.
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.
KYLIN, H. (1932). Die Florideenordnung Gigartinales. Lunds Univ. Årsskr. N.F. Avd. 2, 28 (8), 1–88, Plates 1–28.
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 163A, 164 A–D.
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 164 enlarge
Fig. 164. A–D. Mychodea spinulifera (A–C, AD, A34186; D, AD, A34189). A. Branch with procarps in slightly swollen bases of laterals. B. Section of cortex with a polycarpogonial supporting cell. C. Section of cortex with sunken spermatangial clusters. D. Section of cortex with young and mature tetrasporangia. Mychodea aciculare (E, AD, A44713; F, G, AD, A33483; H, I, AD, A44708; J, AD, A44710). E. Branches with the endo-epiphytic hydrozoan. F. Transverse section of mature branch. G. Section of branch with polycarpogonial supporting cells. H. Branch with mature cystocarps and emerging hydrozoan. I. Section of cortex with sunken spermatangial clusters. J. Section of cortex with young and mature tetrasporangia. [A–J after Kraft 1978.]
State Herbarium of South Australia