Electronic Flora of South Australia Species Fact Sheet

Doxodasya hirta (J. Agardh) Womersley & Parsons, comb. nov.

Phylum Rhodophyta – Family Rhodomelaceae – Tribe Lophothalieae

Synonym

Dasya hirta J. Agardh 1894: 82. De Toni 1903: 1193. Lucas 1912: 157. Lucas & Perrin 1947: 311.

Thallus (Fig. 118A) dark red-brown, 2–10 cm high, much branched radially and irregularly with long, slender, main branches bearing alternate laterals for 4 or 5 orders. Larger branch axes 400–500 µm in diameter, tapering to 30–40 µm in diameter just below apices, clothed throughout (Fig. 118B) with rhodoplastic trichoblasts and similar adventitious filaments 200–300 µm long. Cortication commencing many segments below apices, moderate on lower branches, with the pericentral cells remaining clear (Fig. 118C) and thick walled in transverse section. Holdfast fibrous, small; probably epilithic. Structure monopodial, with a domed apical cell and axial cells (from 4–5 below apices) cutting off trichoblasts in spiral order; the 4 pericentral cells are cut off shortly below. Trichoblasts (Fig. 118D) rigid but with lax, long, ends, 300–1000 µm long with 2–5 branches in varying planes and usually 1–2 cells apart near the base, then with long, unbranched ends; lower and mid cells (10–) 20–30 µm in diameter and L/D (1–) 1.5–2.5, tapering evenly to upper cells 5–7 µm in diameter and L/D 3–6, terminal cell pointed; branch dichotomies with adherent lower walls (as in Dasya).

Adventitious filaments similar to trichoblasts, arising from cortical cells and sparse to prolific on lower branches. Lateral branches arise from base of trichoblasts. Cells uninucleate; rhodoplasts discoid.

Reproduction: Gametophytes dioecious. Procarps (Fig. 118D) developed on second cell of trichoblasts, with 5 pericentral cells, the adaxial one developing a carpogonial branch and probably sterile cells. Carposporophytes with a small basal fusion cell and branched gonimoblast filaments with clavate terminal carposporangia 20–30 µm in diameter, replaced from below. Cystocarps (Fig. 118E) urceolate, base globose and 400–600 µm in diameter, with a short but distinct neck; pericarp ostiolate, 2–3 cells thick. Spermatangial organs on lower branches of trichoblasts, with a sterile basal cell and upper sterile filament, 40–100 µm long and 20–35 µm in diameter (possibly juvenile).

Tetrasporangia in lesser branches (Fig. 118F) with normal trichoblasts, fertile parts 0.5–1 mm long and 80–110 µm in diameter, with paired decussate tetrasporangia 30–55 µm in diameter, each with 2–3 cover cells.

Type from Port Phillip Heads, Vic. (Wilson, 25.i.1893); holotype in Herb. Agardh, LD, 43932, isotype in MEL, 1006687).

Selected specimens: Port Stanvac, S. Aust., 3 m deep on jetty pylon (R. Lewis, 19.ix.1972; AD, A42704). Port Noarlunga, S. Aust., 19 m deep on tyre reef (Branden, 26.iii.1987; AD, A57442).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Only known from Port Phillip Heads, Vic., and eastern coast of Gulf St Vincent, S. Australia.

References:

AGARDH, J.G. (1894). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3. pp. 775–1521 + 1523–1525. (Padua.)

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

LUCAS, A.H.S. (1912). Supplementary list of the marine algae of Australia. Proc. Linn. Soc. N.S.W. 37, 157–171.

The Marine Benthic Flora of Southern Australia Part IIID complete list of references.

Author: H.B.S. Womersley & M.J. Parsons

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. 118.

Figure 118   enlarge

Fig. 118. Doxodasya hirta (A, C–F, AD, A57442; B, AD, A42704). A. Habit. B. Axis and lateral branches with trichoblasts and adventitious filaments. C. Transverse section of axis with bases of adventitious filaments. D. Upper branch with trichoblasts bearing procarps on their suprabasal segment. E. Cystocarp. F. Branches with paired, decussate, tetrasporangia.

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