Electronic Flora of South Australia Species Fact Sheet

Callithamnion circinnatum Womersley, sp. nov.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Callithamnieae

Thallus (Fig. 111A) erect, densely tufted, medium to dark red-brown, 4–12 cm high, ecorticate throughout, with much branched axes and main branches (Fig. 111B) bearing radially lateral branchlets from each cell, usually positioned below the cross wall and often becoming further distant as the axial cells elongate; lower laterals usually with recurved branches (Fig. 111C). Attachment by rhizoids from lower axial cells; epilithic, on solid substrate or epiphytic on Heterozostera. Structure. Lower and mid axes 90–130 µm in diameter, cells L/D 8–15 below, L/D 4–6 in mid thallus, decreasing to upper axial cells 50–80 µm in diameter and L/D (1–) 2–3. Lateral branchlets usually 8–12 cells long with 2–4 branches, tapering over 4–8 cells, lower cells 25–35 µm in diameter and L/D (1–) 2–3, decreasing to 15–20 µm in diameter and L/D 1–3 at 3–4 cells from tips, then tapering to apical cells 6–9 µm in basal diameter, pointed or with rounded ends, Cells uninucleate; rhodoplasts discoid, becoming ribbon like in older axial cells.

Reproduction: Gametophytes probably dioecious. Procarps frequent (often on each second cell) on axial cells near branch apices, 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 (Fig. 111D) and rounded groups (100–200 µm across) of carposporangia 25–35 µm in diameter; carposporophytes involucrate (Fig. 111E) by simple branchlets from lower cells. Spermatangia unknown.

Tetrasporangia (Fig. 111F) usually adaxial on cells of the branchlets, sessile, subspherical, 90–100 µm in diameter, tetrahedrally divided.

Type from Port Noarlunga, S. Aust., 19 m deep on tyre reef (Branden, 26.iii.1987); holotype in AD, A57453.

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

Taxonomic notes: C. circinnatum appears to be a distinctive species, marked by the tapering determinate branchlets, long lower axial cells usually with circinnate branchlets from lower axial cells, and involucral branchlets around the carposporophyte.

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. 111.

Figure 111   enlarge

Fig. 111. Callithamnion circinnatum (A–C, E, AD, A57453; D, AD, A35021; F, AD, A46048). A. Habit. B. Branch systems. C. Lower branches with circinate lateral branchlets. D. Twinned carposporophytes on axial cell. E. Twinned (unequal) carposporophytes with involucral branchlets from lower cells. F. Branches with tetrasporangia.

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