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Dasya divergens Parsons & Womersley, sp. nov.

Phylum Rhodophyta – Order Ceramiales – Family Dasyaceae


Dasya velutina J. Agardh 1890a: 99, nom. illeg. [a later homonym of D. velutina Sonder 1845: 53 = Wrangelia velutina (Sonder) Harvey 1855a: 546]. Lucas 1912: 158; 1929b: 52. Lucas & Perrin 1947: 316. Sonder 1848: 179.

Wrangelia velutina sensu Womersley 1950: 181 in part.

Reproduction: Gametophytes dioecious. Procarps borne successively and spirally on a polysiphonous lateral; the first sterile group initial is cut off from the fertile pericentral cell on the sixth segment, and by the ninth segment a mature procarp with a 4-celled carpogonial branch and two sterile group initials is present; after fertilisation, the sterile group initials each divide once. The auxiliary cell fuses with the central cell of the fertile segment via a new connection, and produces three primary gonimoblast initials, then a monopodial gonimoblast often branching unilaterally. Carposporophyte with a slight basal fusion cell, carposporangia ovoid to subspherical, 15–22 µm in diameter, in rows of 3–4 (–5) often with 1 (–2) lateral sporangia on the basal one. Cystocarps sessile on laterals or on short polysiphonous stalks, globose, 700–1100 µm in diameter with a neck 0.2–0.5 as long as the cystocarp diameter; pericarp 3–4 cells thick with outer cells ovoid to elongate, irregularly placed. Spermatangial branches as ultimate branches of pseudolaterals, lanceoid, 90–170 µm long and 30–40 µm in diameter, with a 1–2 celled pedicel and sterile apex 3–5 cells long, and 6–10 axial cells cutting off initials and an outer layer of spermatangia.

Stichidia borne on the lower branches of pseudolaterals, on 1–3-celled monosiphonous stalks, cylindrical, 300–600 µm long and 120–150 µm in diameter, with (4–) 7–20 fertile segments each with (5–) 6 pericentral cells all of which become fertile, and with a short, mucronate, 2–3-celled apex. Tetrasporangia 25–35 µm in diameter, each with (2–) 3 cover cells, initially small but at maturity covering most of the sporangium.

Type from Robe, S. Aust., drift in bay (Parsons, 9.ii.1982); holotype in AD, A53347, tetrasporangial. lsotype in CHR, 391866.

Selected specimens: 16 km E of Eucla, W. Aust., drift (Womersley, 3.ii.1954; AD, A19304). Head of Great Australian Bight. S. Aust.. drift (Parsons, 4.xi. 1968; AD, A35131; CHR, 315471, 315475). Scott Bay, S. Aust., upper sublittoral pools (Womersley, 27.i.1951; AD, A13924). Elliston, S. Aust., drift (Womersley, 13.i.1951; AD, A13559 ) and 7 m deep (Shepherd, 21.x.1970; AD, A37562; CHR, 315347). West Bay, Kangaroo

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

Distribution: 16 km E of Eucla, W. Aust. to Walkerville, Victoria

Taxonomic notes: Thallus (Fig. 205A) light grey-red to dark red, not mucilaginous and not adhering to paper on drying, 5–15 (–20) cm high, spreading, with 1–3 corticated axes 1–2 mm in diameter bearing irregular patent laterals densely covered (except near the base) with tufts of branched pseudolaterals. Main axes bearing, irregularly radially, laterals of various lengths at intervals of 1–5 mm; axes 0.2–1 mm in diameter, 0.5–3 cm long, more or less linear, moderately heavily corticated from close to their apices, arising from the basal cell of the first branch of the pseudolaterals. Holdfast discoid, loosely rhizoidal, 0.5–1.5 cm across; epilithic. Structure. Pericentral cells 5, always clear in section but corticated outwardly by slenderer rhizoids. The first pericentral is cut off 5–6 segments from the apex, and by the time the fifth pericentral cell is formed (on segments 8 or 9) a secondary pit-connection is established via a small cell from the whole lower end of the pericentral cell; later secondary pit-connections arise via cells cut off from near the end of a pericentral cell. The first corticating rhizoids form from pericentral cells 17–20 segments from the apices, and descend over the pericentral cells. Pseudolaterals one per segment, 1–1.5 mm long, with 5–12 subdichotomies every 1 (–2) cells from their base, of similar diameter until the ultimate branch of (2–) 3–5 (–8) cells which tapers to an acute point; branches divariate, rigid, lying at right angles at each branching; basal cells 50–70 (–100) µm in diameter and L/D 0.5–1.5, mid cells (40–) 45–70 µm in diameter and L/D (1–) 2–3 (–4). Adventitious monosiphonous filaments absent. Rhodoplasts discoid to elongate, becoming chained.

S. Aust., drift (Womersley, 6.i.1946; AD, A3226). Pennington Bay, Kangaroo I., S. Aust., drift (Womersley, 20.v.1945; AD, A2614). Point Lonsdale, Vic., drift (Houlihan, 30.v.1963; MELU, 1591; CHR, 316085). Walkerville, Vic., at low tide level (Sinkora A1524, 21.0.1972; AD, A42312).

Gordon (1972, p. 27) clarified the confusion between Wrangelia velutina (Sonder) Harvey and Dasya velutina J. Agardh, two taxa of very similar habit, and the Dasya is here described as a new species.

D. divergens occurs from upper sublittoral pools to 20 m deep, fertile in summer to late autumn.


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

GORDON, E.M. (1972). Comparative morphology and taxonomy of the Wrangelieae, Sphondylothamnieae and Spermothamnieae (Ceramiaceae, Rhodophyta). Aust. J. Bot. suppl. 4, 1–180.

HARVEY, W.H. (1855a). Some account of the marine botany of the colony of Western Australia. Trans. R. Jr. Acad. 22, 525–566.

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.

LUCAS, A.H.S. (1929b). A census of the marine algae of South Australia. Trans. R. Soc. S. Aust. 53, 45–53.

SONDER, O.G. (1845). Nova Algarum genera et species, quas in itinere ad oras occidentales Novae Hollandiae, collegit L. Preiss, Ph.Dr. Bot. Zeit. 3, 49–57.

SONDER, O.W. (1848). Algae. In Lehmann, C., Plantae Preissianae. Vol. 2, pp. 161–195. (Hamburg.)

WOMERSLEY, H.B.S. (1950). The marine algae of Kangaroo Island. III. List of Species 1. Trans. R. Soc. S. Aust. 73, 137–197.

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. 205.

Figure 205 image

Figure 205   enlarge

Fig. 205. Dasya divergens (A, B, AD, A53347; C, AD, A19304; DAD, A67087; E, F, AD, A20100). A. Habit of holotype. B. Transverse section of branch. C. A cystocarp. D. Spermatangial branches. E. Pseudolaterals with young stichidia. F. Older stichidia.

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