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Ceramium monacanthum J. Agardh 1894b: 29.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Ceramieae

Selected citations: De Toni 1903: 1468. Dixon 1960a: 345; 1960b: 382, 384, 389, fig. 5. Guiler 1952: 98. Huisman & Walker 1990: 422. Lucas 1909: 53; 1929a: 26. Silva et al. 1996: 400. Womersley 1978: 214, figs 1C, D, 5D–G.


C. paniculatum sensu Cribb 1954: 8, 35. (NON Okamura 1896: 36).

Thallus (Fig. 176D) dark red, mostly erect, 0.5–1.5 cm high, branches dense, subcomplanate near apices, usually becoming irregular below, alternate (to subdistichous), 3–8 axial cells apart. Attachment by tufts of rhizoids from the base of erect axes or from short horizontal filaments, rhizoids arising from periaxial cells, uniseriate, simple or sparingly branched (sometimes with a multicellular attachment pad on Corallina); usually epiphytic on Codium fragile and Corallina. Structure. Branches 200–550 µm in diameter below, tapering slightly to 100–150 µm near the involute apices. Axial cells more or less isodiametric, slightly shorter than broad in younger parts and slightly longer than broad in lower parts, with internodal spaces throughout. Periaxial cells 7–8, each cutting off 2 (–3) smaller cortical cells acropetally and basipetally to form the nodal bands (Figs 176E, 177D) 4–6 cells long when young and bearing relatively coarse spines (Figs 176F, G, 177C); node extending by fairly synchronous growth (Fig. 176E) but short internodal spaces present throughout the thallus, usually with long internodes in basal filaments. Spines usually single at each node, occasionally less common, abaxial, with a multicellular base and 3–6 cells (30–100 µm) long (Fig. 176G, 177C), usually lost from older parts of thallus. Rhodoplasts discoid in cortical cells, linear in axial cells.

Reproduction: Gametophytes dioecious. Carposporophytes globular, 180–300 µm across, borne on upper branches and usually subtended by lateral branchlets, with angular carposporangia 20–35 µm across. Spermatangia (Fig. 176F) in dense patches covering the adaxial side of the nodal band, later spreading around the node.

Tetrasporangia (Fig. 176C) cut off from periaxial cells, at first single and abaxial, with later sporangia arising near the first and sometimes extending around the node, partly to largely involucrate by the cortical cells, 35–60 µm in diameter, tetrahedrally divided.

Type from Georgetown, Tas. (Gunn), on Codium; holotype in Herb. Agardh, LD, 21162.

Selected specimens: Cape Willoughby, Kangaroo I., S. Aust., rockpool (Womersley, 8.i.1950; AD, A12942). Robe, S. Aust., on Corallina, low eulittoral pools on reef edges (Womersley, 9.ix.1968; AD, A32694 -"Marine Algae of southern Australia" No. 186). and on Codium fragile, upper sublittoral pools, slipway reef (Womersley, 13.v.1972; AD, A42260). Cape Bridgewater, Vic., 1–2m deep in shaded pool (Womersley, 15.x.1985; AD, A56959). Wine Glass Bay, Freycinet Pen., Tas., on Haliptilon, upper sublittoral pools (Wollaston & Mitchell, 2.iii.1964; AD, A27908). Long Bay, Port Arthur, Tas., on Cystophora torulosa, upper sublittoral (Cribb 160.19, 16.x.1951; AD, A21030). Remine, Tas., on Codium fragile, reef pools (Wollaston & Mitchell, 25.ii.1964; AD, A27506). Green Point, Marrawah, NW Tas., on Codium fragile, sublittoral fringe pools (Bennett 5, 29.i.1955; AD, A20618).

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

Distribution: Cape Willoughby, Kangaroo I. and Robe in S. Aust, to Bridgewater Bay, Vic., and around Tasmania.

Taxonomic notes: C. monacanthum is a distinctive species in south-eastern Australia, and most records are epiphytic on Codium fragile or Corallina, at a low eulittoral or uppermost sublittoral level. It differs from C. puberulum, the only other spinous southern Australian species, in having only a single, usually massive, spine at each node and in the internodal spaces remaining distinct throughout the thallus. The form of the rhizoids depends on the host: on Codium the rhizoids form a dense tuft, often branched but with simple ends, penetrating between the utricles, but multicellular pads are often formed on Corallina.

C. monacanthaum was recorded by Huisman & Walker (1990, p. 422) from Rottnest I. W. Aust., on the basis of a Tilden, South Pacific Plants Ser. 2, No. 77 specimen. The specimen is epiphytic on Codium fragile and is almost certainly mislabelled since the host is also confined to SE Australia.


AGARDH, J.G. (1894b). Analecta Algologica. Cont. II. Acta Univ. lund. 30, 1–98, Plate 1.

CRIBB, A.B. (1954). The algal vegetation of Port Arthur, Tasmania. Pap. Proc. R. Soc. Tas. 88, 1–44, Plates 1–10.

DE TONI, G.B. (1903). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 3, pp. 775–1521 + 1523–1525. (Padua.)

DIXON, P.S. (1960a). Studies on marine algae of the British Isles: the genus Ceramium. J. mar biol. Ass. U.K. 39, 331–374.

DIXON, P.S. (1960b). Studies on marine algae of the British Isles: Ceramium shuttleworthianum (Kutz.)Silva. J. mar biol. Ass. U.K. 39, 375–390.

GUILER, E.R. (1952). The marine algae of Tasmania. Checklist with localities. Pap. Proc. R. Soc. Tasmania 86, 71–106.

HUISMAN, J.M. & WALKER, D.I. (1990). A catalogue of the marine plants of Rottnest Island, Western Australia, with notes on their distribution and biogeography. Kingia 1, 349–459.

LUCAS, A.H.S. (1909). Revised list of the Fucoideae and Florideae of Australia. Proc. Linn. Soc. N.S.W. 34, 9–60.

LUCAS, A.H.S. (1929a). The marine algae of Tasmania. Pap. Proc. R. Soc. Tasm. 1928, 6–27.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (University of California Press: Berkeley, Los Angeles & London.)

WOMERSLEY, H.B.S. (1978). Southern Australian species of Ceramium Roth (Rhodophyta). Aust. J. Mar. Freshw. Res. 29, 205–257.

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

Illustrations in Womersley Part IIIA, 1998: FIGS 176 D–G, 177C, D.

Figure 176 image

Figure 176   enlarge

Fig. 176. A–C. Ceramium shepherdii (AD, A47850). A. Branch with carposporophyte. B. Upper branches with spermatangia. C. Branches with tetrasporangia. D–G. Ceramium monacanthum (D, AD, A32694; E–G, AD, A42260). D. Habit. E. Nodal cortication. F. Branch apices with spermatangia. G. Branch apex with tetrasporangia (All as in Womersley 1978, courtesy of Aust. J. Mar. Freshw. Res.)

Figure 177 image

Figure 177   enlarge

Fig. 177. A, B, Ceramium shepherdii (AD, A47850). A. Part of a branch showing periaxial (stippled) and pseudoperiaxial cells, acropetal cortical cells, tapering filaments and tetrasporangia. B. Transverse section of node, showing 6 periaxial cells (stippled), pseudoperiaxial cells and their tapering filaments (dotted), and tapering filaments from acropetal cortical cells (clear). C, D. Ceramium mortacanthum (AD, A42260).C. Spine near branch apex. D. Nodal cortication showing cell lineages from periaxial cells. E, F, Ceramium puberulum (AD, A46416). E. Node near apex of branch with a primary spine. F. Older nodal cortication, with 2 primary spines and several hairs. (All as in Womersley 1978, courtesy of Aust. J. Mar. Freshw. Res.)

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