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Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Family Delesseriaceae
Selected citations: De Toni 1900: 693. Kylin 1924: 9. Lucas 1909: 36. Womersley & Shepley 1982: 335, figs 2A, 7. Wynne 1989a: 514, fig. 2C.
Synonyms
Delesseria armata J. Agardh 1894: 67.
Delesseria microdonthum J. Agardh 1898: 186. De Toni 1900: 691. Kylin 1924: 9. Lucas 1909: 36. Lucas & Perrin 1947: 228.
Thallus (Fig. 19A, B) light to medium red, erect, usually 10–25 cm high, much branched above and often denuded below. Branching is largely abaxial, mature blades 2–5 mm in width, the midrib becoming corticated on older branches. Holdfast hapteroid to 2 cm across with a perennial stipe 2–4 mm thick, often branched, bearing fronds from its apices; epilithic. Structure. All second-order cells produce third-order rows (Figs 16E, 19C, D), and the margins of the blades are usually irregularly and variably dentate with spinous projections resulting from the development of outer third-order rows which usually cut off a few fourth-order cells (Fig. 16E). Some blades have very slight or virtually no spines (Fig. 19C). One of the third-order cell rows, derived from a second-order cell near the thallus margin, takes over further lateral development and gives rise to short rows of fourth-order cells, at first anteriorly and then often posteriorly (Fig. 16E). Older blades may show short, tapering, spinous outgrowths from any of the marginal cells of the blade. Slight cortication of the midrib commences about half-way along young vegetative blades and at their base the midrib area is completely covered by small elongate corticating cells. Cortication increases as the blades mature and in old blades may occupy 0.2–0.25 of the blade width before the wings of the blade are lost and the midrib remains as the terete stipe of the thallus. Cells uninucleate when small, multinucleate when larger; rhodoplasts discoid, chained in larger cells.
Reproduction: Gametophytes probably dioecious. Procarps not observed. Carposporophyte with a fusion complex and much branched gonimoblast filaments, with carposporangia developing terminally and sequentially, sometimes in short chains; carposporangia subspherical to ovoid or slightly pyriform, 50–90 µm in diameter. Cystocarps (Fig. 19E) develop adaxially near the tips of blades, subspherical to slightly urceolate, 1.5–2.5 mm in diameter, with a small ostiole (70–140 in diameter), basally constricted and subsessile on the parent blade, the midrib of which persists as a longer stalk to the cystocarp. Pericarp heavily corticated, 5–9 cells and 200–300 µm thick. Spermatangia not observed.
Tetrasporangia develop in sori (Fig. 19F) on young blades which lack midrib cortication, derived first from the lateral pericentral cells and later from cells of the second- and third-order rows, rarely from cortical cells. Tetrasporangia mature acropetally and then outwards from the midrib, producing 8–10 tetrasporangia across the blade, until the sorus occupies about two-thirds of the blade width; tetrasporangia 110–150 µm in diameter.
Type from Port Phillip Heads, Vic. (Wilson, 29.xii.1891); holotype in Herb. Agardh, LD, 31575; isotypes in MEL, 10057 and BM.
Selected specimens: York I., Recherche Arch., W. Aust., 5–6 m deep (Royce, 8.ii.1960; PERTH, 2285/6). Anxious Bay (off Waldegrave I.), S. Aust., 23 m deep (Shepherd, 25.ii.1978; AD, A49380). Encounter Bay, S. Aust., drift (Alg. Muell., MEL, 10055). Pennington Bay, Kangaroo I., S. Aust., drift (Womersley, 4.i.1948; AD, A6590). Investigator Strait, S. Aust., 33 m deep (Watson, 24.i.1971; AD,
Distribution: Recherche Archipelago, W. Aust., to Port Phillip, Victoria.
Taxonomic notes: A41086). Gulf St Vincent, S. Aust., 40 m deep (AD, A1072). Port Phillip (West Channel), Vic., 14 m deep (Wilson, 28.xii.1883; MEL, 10031).
In size and general habit H. armatum resembles H. harveyanum and H. protendens but is distinguished from these by the cell development of the blade and marginal outgrowths. In contrast with H. protendens where only the inner 6–8 second-order cells form third-order rows, in H. armatum each second-order row cell forms a third-order row, and prominent but somewhat blunt and often irregularly developed spines occur. In contrast with H. harveyanum where the spines are formed by projecting second-order rows, in H. armatum the end of the second-order rows becomes inactive and the outermost third-order row extends out to form the spine, usually cutting off a few fourth-order cells.
Only a few cystocarpic and tetrasporangial plants have been seen and reproductive stages need further studies.
H. microdonthum J. Agardh is based on material from Port Elliot, S. Aust. (Hussey, Mar. 1898; holotype in LD, 31556), which agrees well with H. armatum. Other specimens from this area show marginal spines to be less developed than some of the specimens from further east (e.g. Port Phillip, Vic.), but of similar construction.
A consistent feature in all examined specimens of this species is the heavy growth of encrusting coralline algae over the blades, more so than on other Australian species of Hypoglossum.
The known range of distribution of this species is similar to that of H. protendens and records suggest that both are plants from deep water (usually 20–35 m), possibly with strong water movement.
References:
AGARDH, J.G. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.
AGARDH, J.G. (1898). Species Genera et Ordines Algarum. Vol. 3, Part 3 - De dispositione Delesseriearum. (Gleerup: Lund.)
DE TONI, G.B. (1900). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 2. pp. 387–776. (Padua.)
KYLIN, H. (1924). Studien über die Delesseriaceen. Lunds Univ. Årsskr. N.F. Avd. 2, 20(6), 1–111.
LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)
LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.
WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1982). Southern Australian species of Hypoglossum (Delesseriaceae, Rhodophyta). Aust. J. Bot. 30, 321–346.
WYNNE, M.J. (1989a). A reassessment of the Hypoglossum group (Delesseriaceae, Rhodophyta), with a critique of its genera. Helgol. Meeresunters. 42, 511–534.
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.
Illustrations in Womersley Part IIIA, 2003: FIGS 16E, 19.
Figure 16 enlarge
Fig. 16. A. Hypoglossum revolutum (AD, A37017)). Cell lineages, cells of second-order rows stippled. B, C. Hypoglossum heterocystideum (AD, A32138). B. Juvenile blade. C. Cell lineages, mid blade. D. Hypoglossum harveyanum (AD, A49090). Cell lineages, mid blade. E. Hypoglossum armatum (AD, A49380). Cell lineages, mature blade. F. Hypoglossum protendens (AD, A42964). Cell lineages, mid blade. G, H. Hypoglossum dendroides (AD, A37557). G. Blade apex. H. Sectional views of apices and formation of transverse pericentral cells (as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.).
Figure 19 enlarge
Fig. 19. Hypoglossum armatum (A, AD, A1072; B–E, AD, A49380; F, AD, A41086). A. Habit. B. Habit, cystocarpic plant. C. Apex of blade with only slight marginal spines. D. Blade with prominent marginal spines. E. Blade with young cystocarp. F. Tetrasporangial sorus. (All as in Womersley & Shepley 1982, courtesy of Aust. J. Bot.)
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