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Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Family Rhodomelaceae – Tribe Polysiphonieae
Thallus (Fig. 77E) dark red-brown, 10–18 cm high, with slight prostrate basal filaments and numerous erect, profusely branched tufts with some percurrent filaments, upper branchlets fastigiate, with occasional small lateral branchlets forming recurved tendrils. Recurved tendrils small, usually less than 1 mm across, formed from about 20 segments at branch ends, present on prostrate and lower branches. Structure. Basal prostrate filaments 250–300 µm in diameter with segments L/D about I, attached by unicellular rhizoids which are not cut off from the pericentral cells and by hooked tendrils; erect axes 200–250 µm in diameter with segments L/D 3–6 (–8), decreasing in lesser branches to 100–150 µm in diameter with segments L/D 1–1.5 and to 50–80 µm in diameter with segments L/D 0.6–1 close to the apices; apices straight, shortly pointed, trichoblasts profuse; lateral branches replacing trichoblasts; occasional cicatrigenous branches present. Pericentral cells 4, elongate throughout the thallus, ecorticate (Fig. 77F); trichoblasts (or scar cells) formed on every segment, with a divergence of 1/4, relatively slender but often persistent for many segments from the apices. Rhodoplasts discoid, scattered or chained.
Reproduction: Carposporophytes with a small basal fusion cell and short, branched gonimoblast with clavate terminal carposporangia 25–50 µm in diameter. Cystocarps (Fig. 77F, G) short stalked, ovoid to slightly pyriform, non-urceolate, 300–400 µm in diameter; pericarp ostiolate, 2 cells thick, outer cells isodiametric, angular. Spermatangial branches unknown.
Tetrasporangia (Fig. 77H) in subulate branch ends or short laterals, gently spirally arranged and usually with a regular size gradation to the tip, mature sporangia occupying most of the width of the branch but scarcely distorting it, subspherical, 80–120 µm in diameter, tetrahedrally divided.
Type from 3 km SE of Troubridge I. S. Aust., 24 m deep (Shepherd, 5.ii.1969); holotype in AD, A33838.
Selected specimens: Off Waldegrave I., S. Aust., 21 m deep (Shepherd, 30.x.1983; AD, A54507). Off Troubridge Light, S. Aust., 18 m deep (Shepherd, 4.ii.1969; AD, A33568). Edge of Tapley Shoal, S. Aust., 13 m deep (Mitchell, May 1961; AD, A28103). Investigator Strait, S. Aust., 33 m deep (Watson, 20.i.1971; AD, A38584).
Distribution: Only known from near the type locality, Waldegrave I. and Investigator Strait, S. Australia.
Taxonomic notes: P. shepherdii is a deep-water species characterised by the rhizoids not being cut off from pericentral cells, by profuse trichoblasts on every segment, by the small hooked tendril branches, and by the dimensions and habit of the thallus. It is a large species, distinct from the other species with such rhizoids in size and robustness (c.f. P. scopulorum and P. subtilissima) or in branch morphology (P. senticulosa), as well as in forming trichoblasts on every segment.
References:
WOMERSLEY, H.B.S. (1979). Southern Australian species of Polysiphonia Greville (Rhodophyta). Aust. J. Bot. 27, 459–528.
The Marine Benthic Flora of Southern Australia Part IIID complete list of references.
Publication:
Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.
Illustration in Womersley Part IIIA, 2003: FIG. 77 E–H.
Figure 77 enlarge
Fig. 77. A–D. Polysiphonia haplodasyae (A, B, D, AD, A3I892; C, AD, A68436). A. A complete cystocarpic plant. B. Immature and mature cystocarps. C. Spermatangial branches (young?). D. A tetrasporangial plant. E–H. Polysiphonia shepherdii (AD, A33838). E. Habit. F. Branches with cystocarps. G. Median view of mature cystocarp. H. Tetrasporangial branches. (All as in Womersley 1979, courtesy of Aust. J. Bot.)
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