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Electronic Flora of South Australia Species Fact Sheet

Ptilocladia gracilis (J. Agardh) Womersley, comb. nov.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Crouanieae

Synonym

Crouania gracilis J. Agardh 1876: 85; 1879: 37, pl. II figs 1–7. De Toni 1903: 1418. Guiler 1952: 98. Lucas 1909: 51; 1929a: 25. May 1965: 366. Sonder 1881: 12. Wollaston 1968: 245.

Thallus (Fig. 20B) 3–18 cm high, medium red to grey-red, slender, irregularly much branched, branches terete with distinct and separated whorls (Fig. 20C) of whorl-branchlets, branches 500–700 µm in diameter in lower thallus, tapering to 130–180 µm in diameter just below apices. Holdfast small (0.2–0.5 mm across), rhizoidal; probably epilithic. Structure. Axes with short apical cells 10–15 µm in diameter and L/D 0.5–1, in young branches axial cells 20–30 µm in diameter and L/D 3–4, increasing to 200–400 µm in diameter and L/D 1–2 in lower thallus, becoming corticate well below the apices but cortical filaments (Fig. 20E) relatively loose and outside the wall sheath, spreading from the nodes, 10–25 µm in diameter with long cells and numerous branched anticlinal filaments. Lateral branches originating from axial cells. Whorl-branchlets 4 per axial cell, 100–180 µm and 6–8 cells long, subdichotomous or trichotomous basally, basal cells 20–25 µm in diameter and L/D 1.2–1.5, tapering to terminal cells 6–10 µm in diameter and L/D 2–2.5; gland cells absent. Cells uninucleate; rhodoplasts discoid, in rows or ribbon-like in older cells.

Reproduction: Gametophytes dioecious. Procarps on axial cells, replacing a whorl-branchlet, with a larger, rounded, supporting cell bearing a 4-celled carpogonial branch. Post-fertilization the auxiliary cell produces a single gonimolobe 90–160 µm across of ovoid carposporangia 25–45 µm in diameter, surrounded by considerably longer whorl-branchlets (Fig. 20F) from lower cells. Spermatangia unknown.

Tetrasporangia (Fig. 20D) occur mostly on basal cells of whorl-branchlets, sessile, subspherical, 80–100 µm in diameter, tetrahedrally divided.

Type from Tasmania (Gunn); holotype in Herb. Agardh, LD, 20269, isotype in MEL, 8438.

Selected specimens: Investigator Strait, S. Aust., 33 m and 34 m deep (Watson, 20.i.1971; AD, A38585 and AD, A39208), 33 m deep (Watson, 4.i.1971; AD, A41083) and 31 m deep (Watson, 23.i.1971; AD, A41096).


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

Distribution: N Tasmania and Investigator Strait, S. Australia.

Taxonomic notes: P. gracilis is a slender species characterised by whorls of 4 whorl-branchlets, absence of gland cells, loose cortication with filaments at least largely outside the axial cell sheath, and very large tetrasporangia (80–100 µm in diameter). These features are shown in the type, which probably came from the north coast of Tasmania, and in the above deep-water specimens from Investigator Strait, though the latter are smaller (4–8 cm high) than the 18 cm high type specimen.

References:

AGARDH, J.G. (1876). Species Genera et Ordines Algarum. Vol. 3, Part 1- Epicrisis systematic Floridearum, pp. i-vii, 1–724. (Weigel: Leipzig.)

AGARDH, J.G. (1879). Florideernes morphologi. K. Svenska Vetensk. Akad. Handl. 15(6), 1–199, Plates 1–33.

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

GUILER, E.R. (1952). The marine algae of Tasmania. Checklist with localities. Pap. Proc. R. Soc. Tasmania 86, 71–106.

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

LUCAS, A.H.S. (1929a). The marine algae of Tasmania. Pap. Proc. R. Soc. Tasm. 1928, 6–27.

MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S.W. natn. Herb. 3, 349–429.

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

WOLLASTON, E.M. (1968).Morphology and taxonomy of southern Australian genera of Crouanieae Schmitz (Ceramiaceae, Rhodophyta). Aust. J. Bot. 16, 217–417.

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

Author: E.M. Wollaston & H.B.S. Womersley

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia


Illustration in Womersley Part IIIA, 1998: FIG. 20 B–F.

Figure 20 image

Figure 20   enlarge

Fig. 20. A. Ptilocladia australis (AD, A33502) Habit. B–F. Ptilocladia gracilis (B, F, AD, A41083; C–E, AD, A39208). B. Habit. C. Young and mid branches with tetrasporangia. D. Branch with tetrasporangia. E. Older corticated branch. F. Lateral branches with carposporophytes in apices surrounded by whorl-branchlets.


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