Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Gigartinaceae
Thallus (Fig. 97A) dark red to brown-red, erect and rigid, cartilaginous, 5–17 cm high, with one to several fronds. Fronds with percurrent, smooth, terete axes, irregularly laterally branched, 0.5–1.5 (–2) mm in diameter, bearing irregularly radial (occasionally subdistichous) terete laterals, lesser ones usually crowded, 2–5 mm long and 0.5–0.8 mm in diameter, with acute to rounded apices, straight to slightly curved. Holdfast discoid, 2–5 mm across; epilithic. Structure of a dense cortex of slender, anticlinal, subdichotomous filaments, outer cells 1–2 µm in diameter and LID 1–2, and a medulla of slender, anastomosing filaments, the central ones thicker and more longitudinal.
Reproduction: Sexual thalli monoecious. Carpogonial branches 3-celled, borne on inner cortical (supporting) cells in lesser branchlets. Cystocarps (Fig. 100A) 0.5–1 mm across, subapical and lateral with a spinous apex to the branchlet, without involucral ramuli, with prominent enveloping tissue 5–8 cells thick with gonimoblast filaments connecting to the inner cells but without transverse filaments, and the carposporophyte (Fig. 97B) consisting of a filamentous matrix with scattered larger cells and clusters of ovoid carposporangia (10–) 14–18 µm in diameter, released through a distinct cortical depression enlarged later by cortical disintegration. Spermatangial sori inconspicuous, often surrounding developing cystocarps, with elongate spermatangia cut off from surface cortical cells and each producing a single ovoid spermatium about 1 µm in diameter.
Tetrasporangial sori (Fig. 100B) forming irregular patches on lesser branches, often forming incomplete annuli 1–3 mm long, tetrasporangia (Fig. 97C) formed only by transformation of inner cortical and outer medullary cells, ovoid, 12–20 µm in diameter and 22–30 µm long, cruciately divided.
Type from Dutton Bay, Portland, Vic., drift (Womersley, 13.iv.1959); holotype in AD, A22670.
Selected specimens: Venus Bay, S. Aust., drift (Womersley, 12.ii.1954; AD, A19497). Off Walker Rock, Anxious Bay, S. Aust., 8–10 m deep (Edyvane, 1.x.1982; AD, A53676). Elliston, S. Aust., 10–12 m deep in bay (Shepherd, 23.x.1969; AD, A34944). Sleaford Bay, S. Aust., rear reef pools, shaded (Womersley, 16.ii.1959; AD, A22502). Port Elliot, S. Aust., drift (Womersley, 10.viii.1957; AD, A21116). Pennington Bay, Kangaroo I., S. Aust., sublittoral fringe (Womersley, 6.i.1949; AD, A10787). Stanley Beach, S coast Kangaroo I., S. Aust., drift (Womersley, 7.ii.1956; AD, A20107). Robe, S. Aust., drift (Wollaston, 13.iii.1955; AD, A19910). Walkerville, Vic., drift (Sinkora A1632, 23.ii.1972; AD, A43221). Swansea, Tas. (Perrin 740, Apr. 1935; AD, A49707). Fluted Cape, Bruny I. Tas., 23 m deep (Shepherd, 12.ii.1972; AD, A41910).
Distribution: Venus Bay, S. Aust., to Walkerville, Vic., and the east coast of Tasmania, from low tide level under moderate wave exposure to 10 m deep on rough-water coasts.
Taxonomic notes: This species was first named Gigartina rubra by Sonder on several herbarium specimens and used as a nomen nudum (1881, p. 14). It is here named after Sonder, and is characterised by its terete, largely irregularly radial, rigid branches, with cystocarps terminal in short branchlets and with a cortical depression, and tetrasporangia transformed mostly from inner cortical and outer medullary cells.
G. sonderi is somewhat similar in habit to G. macrocarpa J. Agardh (1876, p. 683) from New Zealand, but the latter has pinnate and compressed branches.
AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1 - Epicrisis systematis Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)
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 97 A–C, 100A, B.
Figure 97 enlarge
Fig. 97. A–C. Gigartina sonderi (A, B, AD, A22670, holotype; C, AD, A53676). A. Habit, cystocarpic plant. B. Section of part of cystocarp. C. Transverse section of branch with shallow, outer medullary tetrasporangial sorus. D–F. Gigartina muelleriana (D, F, AD, A41189; E, AD, A61359). D. Habit. E. Section of part of cystocarp. F. Transverse section of medullary tetrasporangial sorus.
Figure 100 enlarge
Fig. 100. A, B. Gigartina sonderi (A, AD, A20107; B, AD, A49707). A. Branches with cystocarps. B. Branches with tetrasporangial sori. C, D. Gigartina muelleriana (C, AD, A41189; D, AD, .55438). C. Upper branchlets with cystocarps. D. Upper branchlets with tetrasporangial sori. E, F. Gigartina disticha (AD, A54351). E. Upper branchlets with cystocarps and tetrasporangial sori (mixed phase plant). F. Upper branchlets with tetrasporangial sori. G. Gigartina wehliae (AD, A36053). Branchlets with cystocarps. H, L Gigartina pinnata (H, AD, A54353; I, AD, A56935). H. Upper branchlet with cystocarps. I. Upper branchlets with tetrasporangial sori.
State Herbarium of South Australia