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Dasya crescens Parsons & Womersley, sp. nov.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae


D. capillaris Harvey sensu Kützing 1864: 26, pl. 73.

Thallus (Fig. 215A) medium red to dark brown, soft and lax, 5–20 cm high with one to a few slender axes, much branched radially, above with slender tufts of pseudolaterals, denuded below. Axes and main laterals terete, 300–1200 µm in diameter, moderately corticated on lower parts by rhizoids, commencing many segments from apices with filaments first lying between the pericentral cells (Fig. 215B) and forming a light cover on upper branches, below cover complete and cell rows often slightly spiral; segments L/D 1–4 (–6). Holdfast discoid, rhizoidal, 1–3 mm across; epilithic or on shells. Structure. Pericentral cells 5, remaining clear in transverse section without rhizoids between them. Pseudolaterals (Fig. 215C) on every segment, 1–3 mm long, slender, fastigiate, with 3–5 (–8) basal subdichotomies 1–2 cells apart, tapering gradually from an isodiametric basal cell, lower cells 27–36 µm in diameter (with broad sheaths) and L/D 2–3.5 extending to L/D 6–8, then to unbranched ends 6–12 cells long, subapical cells 6–8 µm in diameter and L/D 4–8 (–10). Lateral branches arising on basal cell of pseudolaterals. Rhodoplasts discoid to elongate, often chained.

Reproduction: Gametophytes dioecious. Procarps on a pericentral cell several segments below apices, with a carpogonial branch and 2 sterile groups, with adjacent axial and pericentral cells becoming darkly staining (Fig. 215C). Carposporophytes much branched, with a slight basal fusion cell and terminal clavate to lacrimiform carposporangia 18–30 µm in diameter, replaced from cells below. Cystocarps sessile (Fig. 215C) and lateral on axes which continue growth, broad based and becoming ovoid, 300–900 µm across, with a slight to distinct neck; pericarp with 18–22 erect filaments, ecorticate apart from cells cut off basal outer pericentral cells. Spermatangial branches (Fig. 215D) elongate, cylindrical and tapering near their apices, 200–800 µm long and 20–45 µm in diameter, with 10–20 axial cells each cutting off several initials in an inner layer which produce an outer layer of spermatangia.

Tetrasporangial stichidia (Fig. 215E) lanceoid to cylindrical, 250–1200 µm long and 90–150 µm in diameter, with 8–15 fertile segments each with 5 pericentral cells and tetrasporangia, on a monosiphonous pedicel; apical filament simple or occasionally branched (Fig. 215E). Sporangia subspherical, 25–55 µm in diameter, tetrahedrally divided, partly covered by 3 obloid cover cells.

Type from Port Sorell, N Tasmania, drift (Womersley, 9.xi.1982); holotype and 3 isotypes in AD, A56245; isotype in CHR, 399521.

Selected specimens: N Spencer Gulf, S. Aust., 9 m deep (Shepherd, 13.ix.1973; AD, A44196). Port Turton, Yorke Pen., S. Aust., 8–10 m deep (Kald, 5.ix.1970; AD, A37266). 10 km W of Outer Harbor, S. Aust., 23 m deep (R. Lewis, 10.ix.1972; AD, A42653). Off Grange, S. Aust., 20 m deep on artificial reef (Branden, 4.ix.1985; AD, A56774). American R. inlet, Kangaroo I., S. Aust., drift at jetty (Womersley, 25.viii.1963; AD, A26746). St Leonards, Port Phillip, Vic., 1–3 m deep (Womersley, 9.viii.1959; AD, A23083). Crawfish Rock, Westernport Bay, Vic., 5–10 m deep (Watson, 29.viii.1971; AD, A39387). Georgetown, Tas. (Harvey, Mg. Aust. Exsicc. 206 I). Spring Bay, Triabunna, Tas., drift (Cribb 147.2, 11.vi.1951; AD, A16350). Taroona, Tas., 2–3 m deep (Shepherd, 19.iii.1975; AD, A46149). Great Taylor Bay, Bruny I., Tas., 19 m deep (Shepherd, 14.ii.1972; AD, A42166).

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

Distribution: N Spencer Gulf, S. Aust., to Port Phillip, Vic., and N and E Tasmania.

Taxonomic notes: D. crescens is named for the continued axial growth after fertilisation, leaving the cystocarps in a sessile, lateral position.

D. crescens occurs mainly in sheltered waters. It is characterised by the slight cortication on upper branches, lack of rhizoids between the pericentral cells, pseudolaterals from every segment, cystocarps with terminal clavate to lachrimiform carposporangia and largely ecorticate pericarp, long, slender, spermatangial branches, and 5 tetrasporangia per whorl with obloid cover cells. One stichidium in the type collection had an apical, branched, filament.

Harvey's Alg. Aust. Exsicc. 206 I, as D. capillaris (Illustrated by Kützing 1864, p1. 73) is D. crescens; it differs from the type of D. capillaris in having pseudolaterals on each segment rather than every 2 segments as in the type.


KÜTZING, F.T. (1864). Tabulae Phycologicae. Vol. 14. (Nordhausen.)

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

Author: M.J. Parsons and 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. 215.

Figure 215 image

Figure 215   enlarge

Fig. 215. Dasya crescens (A–D, F, AD, A56245; E, AD, A46149). A. Habit, holotype sheet. B. Cortication of branches. C. Ecorticate branch with young cystocarp. D. Mature cystocarp. E. Spermatangial branches. F. Stichidium with branched apical filament.

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