Electronic Flora of South Australia Species Fact Sheet

Callithamnion confertum Womersley, sp. nov.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Callithamnieae

Thallus (Fig. 115A) erect, mid red-brown, 5–20 mm high, densely tufted with main axes (Fig. 115B) bearing prominent laterals with branchlets 0.5–1.5 mm long and 2–5 orders of branching, all radially branched and ecorticate; some branchlets continue growth as laterals. Attachment by tufted rhizoids from the basal axial cells; epiphytic on Caulerpa brownii, Jania sp. and Laurencia sp. Structure. Lower and mid axes 100–180 (–240) µm in diameter, cells L/D 1.5–3, main laterals 60–90 µm in diameter, cells L/D 2.5–4, lateral branchlets (4–) 6–10 cells long, lower cells 40–65 µm in diameter and L/D 1.5–2.5, tapering to 20–30 µm in diameter and L/D 1–2 at 3–4 cells below their apices, apical cells 8–12 µm in diameter and L/D 1–2, ends rounded. Cells uninucleate; rhodoplasts discoid, ribbon like in larger cells.

Reproduction: Gametophytes probably dioecious. Procarps borne on mid cells of the young indeterminate axes, with two periaxial cells one of which (the supporting cell) bears the 4-celled carpogonial branch; post-fertilization each periaxial cell cuts off an auxiliary cell and forms a rounded gonimolobe (Fig. 115C) 100–220 (–360) µm across of carposporangia 15–35 µm in diameter; involucral branches arise from the axial cell below the carposporophyte. Spermatangia unknown.

Tetrasporangia (Fig. 115D) borne adaxially on cells of the lateral branchlets, sessile, subspherical to ovoid, 40–55 µm in diameter, tetrahedrally divided.

Type from Robe, S. Aust., on Caulerpa brownii in upper sublittoral pools (Womersley, 9.ix.1968); holotype in AD, A32685.

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

Taxonomic notes: Possible specimens: Safety Cove, Port Arthur, Tas., on Laurencia and Jania, 0–1 m deep (Brown & Kenchington, 16.x.1986; AD, A57738 and A57739 resp.).

Callithamnion confertum appears distinct from other Australian species which have been referred to Callithamnion, but further collections and comparisons with other species are needed. It is named after the congested branching of the laterals.

References: The Marine Benthic Flora of Southern Australia Part IIIC

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
©State Herbarium of South Australia, Government of South Australia

Illustration in Womersley Part IIIA, 1998: FIG. 115.

Figure 115   enlarge

Fig. 115. Callithamnion confertum (AD, A32685). A. Habit. B. Branch with carposporophytes. C. Branch with twinned carposporophytes. D. Branch with tetrasporangia.

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