Electronic Flora of South Australia Genus Fact Sheet

Genus SPERMOTHAMNION Areschoug 1847: 334

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Spermothamnieae

Thallus with prostrate filaments attached by digitate haptera, and erect, slightly to moderately and irregularly branched filaments, epilithic or epiphytic. Cells multinucleate.

Reproduction: Gametophytes usually dioecious. Procarps subapical on erect filaments, with the upper 3 cells smaller and the subhypogenous cell larger, the subapical cell bearing 3 periaxial cells, one sterile, one fertile and producing an auxiliary cell, and the supporting cell with a sterile apical cell and a lateral carpogonial branch. Fusion cell involving both auxiliary cells and the hypogenous cell, becoming 2-armed with two gonimoblast groups with terminal carposporangia. Sterile procarp cells not dividing further but the subhypogenous cell usually bearing 4 outer involucral branchlets. Spermatangial heads sessile or pedicellate, ovoid, on upper cells of erect filaments.

Tetrasporangia terminal on short pedicels, becoming clustered, lateral on erect filaments, tetrahedrally divided.

Type species: S. turneri (Roth) Areschoug 1847: 334 [= S. repens (Dillwyn) Rosenvinge 1924: 298].

Taxonomic notes: A genus of 20–30 recorded species (Gordon 1972, p. 119), but many will probably be placed in other genera when their sexual reproduction is known.

Spermothamnion is characterised by the prominent fusion cell incorporating both auxiliary cells and the hypogenous cell, by the lack of an inner involucre from sterile procarp cells, and the presence of outer involucral filaments from the subhypogenous cell.

Two species occur on southern Australian coasts. A third species, S. miniatum Huisman (1985), occurs on N.S.W. and Western Australian coasts, and differs from other species in having involucral filaments only from the axial cell below the subhypogenous cell, the female axis being 4 cells long. Other epilithic species in AD cannot be placed in the absence of female plants, but such tufts 1–3 cm high are not uncommon.

References:

ARESCHOUG, J.E. (1847). Phycearum, quae in maribus Scandinaviae crescunt, enumeratio. Nova Acta R. Soc. Scient. upsal. 3, 223–382, Plates 1–9.

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

HUISMAN, J.M. (1985). Rhipidothamnion secundum gen. et sp. nov. and Spermothamnion miniatum sp. nov. (Ceramiaceae, Rhodophyta) from eastern Australia. Phycologia 24, 55–66.

ROSENVINGE, L.K. (1924). The marine algae of Denmark. Contributions to their natural history. Part III. Rhodophyceae III (Ceramiales). K. danske Vidensk. Selsk. Skr 7, 287–486, Plates 5–7. (Lipsiae.)

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

Author: 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

KEY TO SPECIES OF SPERMOTHAMNION

1. Thallus 1–1.5 mm high, irregularly branched, prostrate filaments 20–35 µm in diameter, erect filaments 20–55 µm in diameter, epiphytic on Xiphophora chondrophylla	S. pinnatum
1. Thallus 1–3 cm high, sparingly and irregularly branched, prostrate filaments 50–100 µm in diameter, erect filaments 65–85 µm in diameter, epilithic, often in sand	S. cymosum

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