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Genus PTEROTHAMNION Nägeli in Nägeli & Cramer 1855: 66.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Pterothamnieae

Thallus usually 4–20 (–30) cm high, with erect, complanately branched, apices often flexuous with laterals usually every 2–8 axial cells, arising in place of whorl-branchlets and often overtopping the previous main axis; each axial cell with 2 or 4 whorl-branchlets; axes ecorticate or loosely to densely corticate with rhizoids on lower axes; holdfast of multicellular rhizoids; epilithic or epiphytic. Structure. Apices of small cells dividing transversely, enlarging below, each axial cell bearing first a single unilateral, then 2 opposite whorl-branchlets in the plane of the thallus, and between them usually 2 alternating, similar sized or shorter, whorl-branchlets; whorl-branchlets successively branched several times usually adaxially, usually bearing sessile gland cells variously orientated, and the basal or other cells with spinous processes in some species; corticating rhizoids arising from the basal cells of whorl-branchlets. Lateral branches arising from axial cells or the basal cells of whorl- branchlets. Cells uninucleate.

Reproduction: Gametophytes dioecious. Procarps usually borne along young axes in series of 2–5 (–20) on basal cells (which act as supporting cells) of successive whorl-branchlets; post-fertilization the auxiliary cell forms a foot cell and a gonimoblast initial, often with later fusion of this initial, the foot cell, residual supporting cell and the axial cell, with a single carposporophyte on each branch, consisting of several rounded gonimolobes surrounded only by whorl-branchlets from lower cells. Spermatangia are cut off from terminal initials on the whorl-branchlets.

Tetrasporangia are borne on cells of the whorl-branchlets, sessile or pedicellate, single or grouped, cruciately or decussately divided, sometimes appearing tetrahedral.

Gametophytes dioecious. Procarps formed on 3–6 (–20) successive pinnae (Fig. 61F) near apices, usually on major pinnae but sometimes on each pinna of a whorl, with the basal (supporting) cell bearing a 4-celled carpogonial branch (Fig. 61G). Post-fertilization a terminal gonimolobe develops and later lateral rounded gonimolobes (Fig. 61H), 100–270 µm across, of ovoid to angular carposporangia 20–25 µm across, partly surrounded by upcurved lower pinnae; only one carposporophyte (Fig. 59B) occurs per branch. Spermatangia (Figs 59C, 61I) occur terminally on special branches, usually densely branched, on lower cells of pinnae and pinnules, ovoid and 3–6 µm in diameter.

Tetrasporangia (Figs 59D, 61J, K) occur laterally on special branches on the inner cells of pinnules, terminal and lateral, ovoid, 37–45 µm in diameter, decussately divided.

Type: Type species: P. plumula (Ellis) Nägeli in Nägeli & Cramer 1855, p. 56.

Type from Port Fairy, Vic., lectotype in Herb. Agardh, LD, 18139 (Harvey, Alg. Aust. Exsicc. 543).

Selected specimens: Robe, S. Aust., drift (Wollaston, 19.v.1964; AD, A27916) and (Womersley, 15.iv.1994; AD. A63553). Nora Creina, S. Aust., drift (Womersley, 6.xii.1995; AD, A64751). Bridgewater Bay, Vic., drift (Beauglehole, 26.x ii.1950; AD, Al 5593). Lady Julia Percy I.. Vic., 18 m deep (Shepherd, 4.i.1968; AD, A32458). Port Fairy, Vic., drift (Woinersley, 24.i.1967; AD, A31499). Sealers Cove, Vic. (Mueller).

Distribution: Robe, S. Aust., to Sealers Cove, Victoria.

Taxonomic notes: Athanasiadis & Kraft (1994) considered that Platythamnion J. Agardh (1892, p. 22) and Glandothamnus Wollaston (1981, p. 113) should be regarded as synonyms of Pterothamnion, within which they include 27 species, with eight species on southern Australian coasts. However, further study is needed of the position of gland cells and possible recognition of more than one genus within the complex.

unbranched pinnae between them; larger pinnae with simple pinnules (inner 1 or 2 sometimes branched) from most cells; rachides of pinnae usually curved backwards, basal cells 45–75 µm in diameter and L/D 1–1.3, tapering to subapical cells 16–24 µm in diameter and L/D 1–1.5 with pinnules only slightly slenderer; apical cells mucronate and apical and subapical cells often with short lateral spines (Fig. 61E); gland cells (Figs 59A, 61C) sessile, usually on third to fifth cells of the rachis and also the corticating rhizoids, hemispherical to subspherical, 40–55 µm in diameter. Lateral branches arising from the basal cells of major pinnae. Cells uninucleate; rhodoplasts elongate in smaller cells, ribbon like in larger cells.

Harvey (1855a, p. 561) recorded Callithamnion simile Hooker & Harvey (a Kerguelin I. species) from Rottnest I. and King George Sound, W. Aust., and later (1862, pl. 207) in his description and illustration, recorded it from Port Fairy and Sealers Cove, Victoria. Harvey's Fremantle, W. Aust., plant (as in MEL, 10625) is Antithamnion armatum, whereas his Port Fairy, Vic., plant (MEL 10268) is Pterothamnion nodiferum. Though superficially similar, the number of whorl-branchlets and the position and size of gland cells clearly distinguish the two species. There appear to be no records of the latter west of Robe, S. Aust., and P. nodiferum appears to be a deep water species on eastern South Australian and western Victorian coasts.


AGARDH, J.G. (1892). Analecta Algologica. Acta Univ. lund. 28, 1–182, Plates 1–3.

ATHANASIADIS, A. & KRAFT, G.T. (1994). Description of Pterothamnion squarrulosum (Harvey) comb. nov. from south-eastern Australia and southern New Zealand, with a taxonomic re-assessment of the genera Pterothamnion, Platythamnion & Glandothamnus (Ceramiaceae, Rhodophyta). Eur. J. Phycol. 29, 119–133.

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

NÄGELI, C. & CRAMER, C. (1855). Pflanzenphysiologische Untersuchungen, Part 1. (Friedrich Schulthess; Zurich.)

WOLLASTON, E.M. (1981). Descriptions of two new genera, Scageliopsis and Glandothamnus (Ceramiaceae, Rhodophyta), including five previously undescribed species from southern Australia. Pacific Sci. 34, 109–127.

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

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

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
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