Electronic Flora of South Australia Species Fact Sheet

Amphiroa gracilis Harvey 1855a: 547; 1862: pl. 231; 1863, synop.: xxix.

Phylum Rhodophyta – Class Florideophyceae – Order Corallinales – Family Corallinaceae – Subfamily Amphiroideae – Tribe Amphiroeae

Selected citations: De Toni 1905: 1809. Huisman & Walker 1990: 411. Johansen 1969: 50 pl. 14C (as Amphiroa sp. but based on Harvey, Alg. Aust. Exsicc. 459A). Lucas & Perrin 1947: 394. Sonder 1881: 20.

Synonym

Metagoniolithon gracile (Harvey) Yendo 1905: 12. Ducker 1979: 96, fig. 15B. Ganesan 1971: 248. Manza 1940: 311. May 1965: 356.

Thallus (Fig. 131A) medium red-brown, fading to grey-red, 4–10 cm high, with several axes from the holdfast, branching usually fastigiate with 2–4 (–6) branches from each intergeniculum, not complanate, intergenicula terete, 4–6 mm long and (1–) 1.5–2 mm in diameter near the base, decreasing evenly to (3–) 4–6 mm long and 300–500 µm in diameter above. Holdfasts crustose, 2–8 mm across, bearing several to numerous fronds; epilithic. Structure multiaxial. Intergenicula (Fig. 131B) of numerous arching tiers of medullary cells, with lateral pit-connections about three-quarters up the cells; single tiers of shorter cells (15–45 µm long) separating every 2–4 (–7) tiers of longer cells (60–90 WTI long), all 9–16 µm in diameter, ends rounded. Genicula (Fig. 131C) ends not corresponding to tiers, similar in structure to intergenicula but cells narrower, thicker walled and darkly staining, with lateral pit-connections. Cortex compact, developed from larger, ovoid, outer medullary cells, consisting of anticlinal filaments of 5–10 ovoid cells (6–) 7–9 µm in diameter, with short epithallial cells, present but less well developed on genicula. Apices of branches with meristematic cells and small epithallial cells. Rhodoplasts discoid to laminate.

Reproduction: Gametangial thalli unknown.

Tetrasporangial conceptacles (Fig. 131D) prominent, 250–500 µm in external diameter, tetrasporangia among elongate cells, 70–110 µm long and 35–55 µm in diameter, zonately divided.

Type from "King George Sound and Rottnest", W. Aust. (Harvey, Tray. Set 218); lectotype (here designated) from Rottnest I, W. Aust.; in TCD.

Selected specimens: Red Bluff, Kalbarri, W. Aust., upper sublittoral pools (Womersley, 15.ix.1979; AD, A51287 -"Marine Algae of southern Australia" No. 199). Port Denison, W. Aust., outer reef pools (Gordon, 8.xi.1968; AD, A33150). Fish Hook Bay, Rottnest I., W. Aust., upper sublittoral (Gordon-Mills, 6.xii.1984; AD, A56660). Fenelon I., Isles of St Francis, S. Aust., 5 m deep (Edyvane, 19.vi.1992; AD, A62134). The Gap, Thorny Passage, NW Thistle I., S. Aust., 4–5 m deep (Branden, 30.ix.1989; AD, A59932, A59933). Louth Bay, S. Aust., upper sublittoral (Womersley, 5.i.1951; AD, A13829). Cable Hut Bay, Yorke Pen., S. Aust., 5 m deep (Edyvane, 27.x.1993; AD, A64426). Troubridge Hill, S. Aust., 5 m deep (Edyvane, 30.x.1993; AD, A64576).

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

Distribution: Kalbarri, W. Aust., to Troubridge Hill, Yorke Pen., S. Aust.

Taxonomic notes: A. gracilis was described from "King George's Sound and Rottnest", based on Harvey's Tray. Set 218. No specimens from King George Sound were located in TCD in 1952, and Harvey's 218 from Rottnest I. (the lectotype) is in fragments. There are three good specimens from "Swan River" in TCD.

A. gracilis occurs on southern Australian coasts as far east as Troubridge Hill, Yorke Peninsula, but it is apparently not common. Structurally it is a typical Amphiroa, but it can superficially resemble slender Metagoniolithon radiatum. However, A. gracilis usually forms more erect, fastigiate tufts with several clustered fronds from the holdfast, the intergenicula decreasing fairly evenly in length from the base upwards.

Ducker (1979, p. 98) queried whether A. gracilis is not synonymous with A. fragilissima, but the latter differs in habit and in having collars at the ends of older intergenicula (Weber-van Bosse 1904, p. 91). Further comparisons with tropical species of Amphiroa are clearly needed.

Metagoniolithon gracile, as recorded in Womersley (1950, p. 167), is now referred to M. chara.

References:

DE TONI, G.B. (1905). Sylloge Algarum omnium hucusque Cognitarum. Vol. 4. Florideae. Sect. 4, pp. 1523–1973. (Padua.)

DUCKER, S.C. (1979). The genus Metagoniolithon Weber-van Bosse (Corallinaceae, Rhodophyta). Aust. J. Bot. 27, 67–101.

GANESAN, E.K. (1971). Studies on the morphology and reproduction of the articulated corallines. VI. Metagoniolithon Weber-van Bosse. Rev. Algol. n.s., 10, 248–256, Plate 21.

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

HARVEY, W.H. (1862). Phycologia Australica. Vol. 4, Plates 181–240. (Reeve: London.)

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

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.

JOHANSEN, H.W. (1969). Morphology and systematics of coralline algae with special reference to Calliarthron. Univ. Calif. Pubins Bot. 49, 1–78, Plates 1–19.

LUCAS, A.H.S. & PERRIN, F. (1947). The Seaweeds of South Australia. Part 2. The Red Seaweeds. (Govt Printer: Adelaide.)

MANZA, A.V. (1940). A revision of the genera of articulated corallines. Philip. J. Sci. 71, 239–316, Plates 1–20.

MAY, V. (1965). A census and key to the species of Rhodophyceae (red algae) recorded from Australia. Contr. N.S.W. natn. Herb. 3, 349–429.

SONDER, O.W. (1881). In Mueller, F., Fragmenta Phytographiae Australiae. Supplementum ad volumen undecinum: Algae Australianae hactenus cognitae, pp. 1–42, 105–107. (Melbourne.)

WEBER-VAN BOSSE, A. (1904). Corallineae verae of the Malay Archipelago. In Weber-van Bosse & Foslie, M., The Corallinaceae of the Siboga Expedition. Siboga-Expeditae, Monogr. LXI, pp. 78–110, Plates 14–16. (Leiden.)

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

YENDO, K. (1905). A revised list of Corallinae. J. Coll. Sci., Imp. Univ. Tokyo 20 (12), 1–46.

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

Author: H.B.S. Womersley & H.W. Johansen

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.

Illustration in Womersley Part IIIA, 1996: FIG. 131.

Figure 131   enlarge

Fig. 131. Amphiroa gracilis (A, AD, A13829; B–D, AD, A64576). A. Habit. B. Longitudinal section of branch apex showing long and short tiers and arcs of lateral pit-connections; spaces due to processing. C. Longitudinal section of genicula and adjacent intergenicula. D. Longitudinal section (broken) of tetrasporangial conceptacle.

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