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Electronic Flora of South Australia Species Fact Sheet

Dasya atactica J. Agardh 1890a: 107, pl. 3 fig. 4.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae

Selected citations: De Toni 1903: 1213. Lucas 1912: 158. Lucas & Perrin 1947: 315.

Thallus (Fig. 214A) medium red, 4–10 cm high, adhering to paper on drying, much branched with one to a few slender axes with well developed laterals, with terminal and lateral pseudolateral tufts, denuded below. Axes and lateral branches terete, 200–400 µm in diameter, moderately corticated (Fig. 214B) on lower parts by rhizoids, commencing many segments from apices and forming a light cover on upper branches, complete cover below; segments L/D 1–3. Attachment rhizoidal; epilithic or on mussels. Structure. Pericentral cells 5, remaining clear in transverse section without rhizoids between them. Pseudolaterals (Fig. 214C) on every segment, 1–1.5 mm long, slender, branches patent with 2–4 basal subdichotomies (1–) 2 (–3) cells apart, tapering from an isodiametric basal cell, lower cells 45–60 µm in diameter and L/D 1.5–2.5 to unbranched ends 8–14 (–20) cells long, subapical cells (15–) 20–30 in diameter and L/D 2.5–3.5; occasional pseudolateral branches (A56314) with moniliform ovoid cells 90–115 µm in diameter. Lateral branches arising on lower cells of pseudolaterals. Rhodoplasts discoid to slightly elongate.

Reproduction: Gametophytes probably dioecious. Procarps unknown. Carposporophytes much branched, with a slight basal fusion cell and terminal rows of ovoid to subspherical carposporangia 20–30 µm in diameter. Cystocarps (Fig. 214C) sessile on lesser branches, ovoid, 0.5–1 mm across, with a distinct and slightly flared neck; pericarp 2 (–3) cells thick, with 12–15 erect filaments, outer pericentral cells becoming irregular and largely ecorticate. Spermatangial branches unknown.

Tetrasporangial stichidia (Fig. 214D, E) lanceoid to cylindrical, 500–900 µm long and 100–120 (–140) µm in diameter, with 6–20 fertile segments each with 5 pericentral cells and sporangia, on a monosiphonous pedicel and often with a terminal, simple or branched, filament up to several cells long; sporangia subspherical, 30–45 µm in diameter, tetrahedrally divided, partly covered by cuboidal to ovoid cover cells (Fig. 214E).

Type from Port Phillip Heads, Vic. (Wilson); lectotype Wilson 61, in Herb. Agardh, LD, 44311.

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

Distribution: Only known from Port Phillip, Victoria.

Taxonomic notes: Selected speicmens: Gellibrand Light, Port Phillip, Vic., 6–8 m deep (Kraft 5698, 9.xii.1975; MELU and AD, A56314). Middle Park (Hobson Bay), Port Phillip, Vic., drift (Sinkora A378, 14.iii.1970; AD, A55580). Swan L, Port Phillip, Vic., 0–0.5 m deep on barge (Womersley, 8.iv.1959: AD, A22599).

J. Agardh distinguished D. atactica on the occasional stichidia which continue apical growth as a branched filament. While such stichidia are distinctive they are not frequent, and are occasionally seen in other species (see below, and also D. crescens and D. cliftonii). The length of branch segments and cystocarps with rows of subspherical carposporangia distinguish D. atactica from D. crescens.

D. atactica has been collected by Kraft and his students from Gellibrand light in all months of the year (1975, 1976), with the largest plants from May to February.

The following collections show apically proliferous stichidia even more strikingly than D. atactica. The thalli are similar but slightly slenderer, the pseudolaterals taper to very slender ends with long cells, and the stichidia (of which A56312 has numerous apically proliferous stichidia) have only 4 sporangia per whorl rather than 5. The carposporangia are ovoid, occurring in rows. These appear to be a distinct species from D. atactica, but this awaits confirmation.

Port Turton, Yorke Pen., S. Aust., 8–10 m deep on rock (Kald, 5.ix.1970; AD, A56312). Port Stanvac, S. Aust., 2 m deep on jetty pylons (R. Lewis, 7.iv.1972; AD, A42478). Bay of Shoals, Kangaroo I., S. Aust., 3 m deep (Womersley, 5.i.1990; AD, A60120). Muston, American R. inlet, Kangaroo I., S. Aust., 2–3 m deep in channel (Kraft, 7.iv.1972; AD, A42416) and (Kraft, Johnson & Wickes, 16.iv.1973; AD, A43752).


AGARDH, J.G. (1890a). Till algernes systematik. Acta Univ. lund. 26(3), 1–125, Plates 1–3.

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 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. 214.

Figure 214 image

Figure 214   enlarge

Fig. 214. Dasya atactica (AD, A56314). A. Habit. B. Branch with moderate cortication and laterals with slight cortication. C. Pseudolateral filaments and a cystocarp. D. Pseudolaterals with stichidia. E. Stichidia showing tetrasporangia and cover cells.

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