Electronic Flora of South Australia Genus Fact Sheet

Genus DASYTHAMNIELLA Silva 1970: 942

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Compsothamnieae

Thallus erect, 5–25 (–50) cm high, with distichous, lateral, indeterminate branches for several orders, developed from determinate branchlets and becoming densely corticated by lax rhizoidal filaments from shortly or more distantly below the branch apices. Active indeterminate apices distichously branched, apical cells dividing obliquely to transversely; lateral determinate branchlets ecorticate, basally branched, terminally unbranched, cells short. Cells multinucleate (2–10 small nuclei per cell).

Reproduction: Gametophytes probably dioecious. Procarps borne on the third and often also the fourth cell of short, 3–8-celled, lateral branches, with 2 (–3) periaxial cells, one bearing a sterile cell and a 4-celled carpogonial branch. Carposporophyte with fusions between basal cells and with 1–4 successive rounded gonimolobes, with or without separate involucral branchlets (apart from lower determinate branchlets), all cells becoming carposporangia. Spermatangia on distinct clusters borne adaxially on branchlets (unknown in type species).

Tetrasporangia sessile or on 1–5-celled pedicels, sometimes clustered by branching from pedicels, situated on determinate ramuli, tetrahedrally divided.

Type species: D. setosa (J. Agardh) Silva 1970: 942 [= D. dasyura (Harvey) comb. nov.]

Taxonomic notes: Antarcticothamnion Moe & Silva (1979, p. 402) is closely related to Dasythamniella but differs in branching pattern, origin of lateral indeterminate branches which arise on main axes as verticils, in binucleate carposporangia and in having polysporangia; the female reproduction in both genera is very similar.

The active apices usually with oblique cell divisions, and the procarpial axes of 3–8 cells with one (or two) procarps on the third and fourth cells, place Dasythamniella in the Compsothamnieae. All the species included below are similar in this respect to the type species, D. dasyura. Dasythamniella is now considered to include Compsothamnionella Itono (1977, p. 42) and differs from Compsothamnion (see Westbrook 1930 and Gordon-Mills & Wollaston 1990) in having usually only 2 periaxial cells on the female axis and developing only a single auxiliary cell compared to 2 in Compsothamnion.

Harvey (1863, synop.: li) had grouped 4 of the species now referred to Dasythamniella, plus species of Spongoclonium, in his Section 1. Dasythamnion of Callithamnion.

References:

GORDON-MILLS, E. & WOLLASTON, E.M. (1990). Compsothamnionella huismanii sp. nov. (Ceramiales, Rhodophyta) from Southern Australia. Bot. Mar. 33, 9–17.

HARVEY, W.H. (1863). Phycologia Australica. Vol. 5, Plates 241–300, synop., pp. i-lxxiii. (Reeve: London.)

ITONO, H. (1977). Studies on the Ceramiaceous algae (Rhodophyta) from southern parts of Japan. Bibliotheca Phycologia 35, 1–499.

MOE, R.L. & SILVA, P.C. (1979). Morphological and taxonomic studies on Antarctic Ceramiaceae (Rhodophyceae). I. Antarcticothamnion polysporum gen. et sp. nov. Br. phycol. J. 14, 385–405.

SILVA, P.C. (1970). Remarks on algal nomenclature. IV. Taxon 19, 941–945.

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

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

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

KEY TO SPECIES OF DASYTHAMNIELLA

1. Mature determinate branchlets 0.5–3 mm long, more or less complanately branched with unbranched ends 200 µm – 2 mm long; tetrasporangia pedicellate	2
1. Mature determinate branchlets 120–900 µm long with crowded branches and not complanately branched, with short unbranched ends 50–400 µm long; tetrasporangia mostly sessile	4
2. Determinate branchlets 1–3 mm long, basally branched with unbranched ends 1–2 mm and 20–50 (–70) cells long; cells isodiametric (L/D 1–1.5)	D. dasyura
2. Determinate branchlets 0.5–1 (–1.5) mm long, alternately branched with unbranched ends (40–) 200–600 µm and (3–) 5–17 cells long, cells elongate, L/D 1.5–3 (–4)	3
3. Thallus fastigiate, much branched with erect lateral branches but without prominent spreading laterals; lateral branchlets lax and not or scarcely overlapping; cortication relatively slight on lower axes	D. latissima
3. Thallus with prominent, spreading, lateral branches, densely branched with overlapping branchlets with curved pinnules; cortication becoming dense on lower axes and lateral branches	D. wollastoniana
4. Lower cells of determinate branchlets 30–40 µm in diameter and L/D 0.8–1, tapering to 15–20 µm in diameter in subapical cells	D. plumigera
4. Lower cells of determinate branchlets 15–25 µm in diameter and L/D 1–2, tapering to subapical cells 6–9 µm in diameter and L/D 2–3	D. superbiens

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