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Electronic Flora of South Australia Species Fact Sheet

Pedobesia clavaeformis (J. Agardh) MacRaild & Womersley 1974: 92, figs 1–15.

Phylum Chlorophyta – Order Derbesiales – Family Derbesiaceae


Bryopsis cladaeformis J. Agardh 1887: 20.

Derbesia clavaeformis (J. Agardh) De Toni 1889: 425. Womersley 1956: 371.

Thallus (Fig. 99C) dark green, epilithic, 3–5 (–6) cm high, of numerous simple, erect, clavate branches (1–) 2–3 mm in diameter, arising from slender, much-branched and lobed filaments; chloroplasts numerous, lenticular, 2–5 µm long, without a pyrenoid but with 1–2 (–3) starch plates within the chloroplast. Prostrate discs (winter state) 2–6 mm in diameter (Fig. 99D), often overgrown by secondary discs, with marginal growth and concentric rings of growth or calcification (Fig. 99D,E) divided into radial sectors (Fig. 99E); discs coenocytic but with internal calcified pillars and calcification (aragonite) within the walls which have numerous pores.

Reproduction: Reproduction by sporangia 350–450 (–1000) µm in diameter, borne subapically on the clavate branches. producing stephanokontic zoospores 30–40 µm in diameter, which produce the disc stage.

Type from Western Port, Vic.; holotype in Herb, Agardh, LD. 14897.

Selected specimens: Point Clune, Rottnest I., W. Aust., 11–13 m deep (Gahric/son, 2.xii.1980; ADU, A51956). On Clan Ranald Wreck, off Troubridge Hill, S. Aust., 20 m deep (Shepherd, 27.xii.1963; ADU, A27315). West Bay, Kangaroo I., S. Aust., drift (Womersley, 6.i.1946; ADU, A3200). Nora Creina, S. Aust., in shaded pool (MacRaild & Womersley, 17.i.1971; ADU, A37816—"Marine Algae of southern Australia" No. 14). Point Lonsdale. Vic., low eulittoral (Ducker, 21.ii.1975; MELU. 21915). Gordon, Tas. (Harada, March 1980; HO, 43040).

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

Distribution: From Point Clune. Rottnest I., W. Aust., and from West Bay, Kangaroo I.. S. Aust. to Cape Patterson, Vic. and Hogan I., Bass Strait, and Gordon, Tasmania. Northern New Zealand.

Taxonomic notes: This distinctive and unusual species has been described in detail by MacRaild & Womersley (1974). It occurs in shaded pools and to 20 m deep. and is probably generally distributed along southern Australia.


AGARDH, J.G. (1887). Till algernes systematik. VIII. Siphoneac. Acta Univ. hind. 23, 1–180. Plates 1–5.

DE TONI, G.B. (1889–1924). Sylloge Algarum omnium hucusque Cognitarium. Vols 1–6. (Padua.)

MacRAILD, G.N. & WOMERSLEY, H.B.S. (1974). The morphology and reproduction of Derbesia clavaeformis (J. Agardh) De Toni (Chlorophyta). Phycologia 13, 83–93.

WOMERSLEY, H.B.S. (1956). A critical survey of the marine algae of southern Australia. I. Chlorophyta. Aust. J. mar. freshw. Res. 7, 343–383.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (31 May, 1984)
The Marine Benthic Flora of Southern Australia
Part I
©Board of the Botanic Gardens and State Herbarium, Government of South Australia

Illustration in Womersley Part I, 1984: FIGS 99 C–E.

Figure 99 image

Figure 99   enlarge

Fig. 99. A.Derbesia marina (ADU, A53085). B. Derbesia tenuisssima(AD U, A20276). C–F. Pedobesia clavaeformisC. Living thallus with sporangia (ADU, A37816 collection). D,E. Prostrate disc, showing concentric growth sectors, and meristematic periphery. E. Surface detail of prostrate disc (culture material, from MacRaild & Womersley 1954, Figs 7.9).

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