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Electronic Flora of South Australia Species Fact Sheet
Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Crouanieae
Thallus (Fig. 15C) light to medium red, erect, 4–15 cm high, slender, with terete axes bearing irregular, often pectinate, lateral branches, branch apices tapering to rounded, axes ecorticate except for slight rhizoidal cortication (Fig. 15E) on lower parts, usually not mucilaginous, with 3 whorl-branchlets per axial cell. Base prostrate, attached by rhizoids from the basal cells of whorl-branchlets; epilithic, on shells or Posidonia. Structure. Apical cells 5–7 µm in diameter and L/D 1–1.5, enlarging to 150–250 µm in diameter and L/D 1.5–2 (–4) in the lower axes, axial cells clearly visible throughout the thallus; lateral branches arising from axial cells. Whorl-branchlets (150–) 200–300 (–400) µm long, with 5–8 di- or trichotomies, almost horizontal or slightly upwardly directed near branch apices, outer parts almost adjacent in side view of thallus, often nodose below; basal cells of whorl-branchlets 9–16 µm in diameter and L/D 1.5–2, tapering to terminal cells 5–7 µm in diameter and L/D (2–) 3–4, often with a hair. Lower axes sparsely corticated (Fig. 15E) by a few multicellular rhizoids 8–15 µm in diameter, arising from the basal cells of whorl-branchlets, not obscuring the axial cells. Cells uninucleate; rhodoplasts discoid in small cells, becoming ribbon like and branched in larger cells.
Reproduction: Gametophytes dioecious. Procarps developed in place of a whorl-branchlet on 1–3 successive subapical cells, with a supporting cell bearing a 4-celled carpogonial branch. Mature carposporophytes (Fig. 15F) have 1–3 rounded groups 200–350 µm across of ovoid carposporangia 20–35 µm across, protected by enlarged surrounding whorl-branchlets in a clavate branch end. Spermatangia occur in whorls of 2–4 cells on terminal cells of whorl-branchlets.
Tetrasporangia (Fig. 15D) occur on basal and next cells of whorl-branchlets, sessile, subspherical, 45–55 µm in diameter, tetrahedrally divided.
Type from 5 km W of Port Noarlunga, S. Aust., 21 m deep on shells (Ottaway, 8.xii.1980); holotype (carposporangial) and isotype (tetrasporangial) in AD, A52115.
Selected specimens: Elliston Bay, S. Aust., 10–12 m deep (Shepherd, 24.x.1969; AD, A34959). Douglas Bank, N Spencer Gulf, S. Aust., 7 m deep (Johnson, 15.iv.1975; AD, A54953). Yatala Harbour, N Spencer Gulf, S. Aust., on Posidonia sinuosa, 7 m deep (Johnson, 1.ix.1977; AD, A54946). 10 km W of Outer Harbor, S. Aust., 23 m deep on wreck of "John Robb" (R. Lewis, 10.ix.1972; AD, A42654). 5 km W of Seacliff, S. Aust., 21 m deep on shells (Ottaway, 11.xii.1980; AD, A52107). Muston, Kangaroo I., S. Aust., 2–3 m deep (Wollaston, 21.xi.1963; AD, A32956). Walkerville, Vic., drift (Sinkora A2394, 25.ii.1978; AD, A53584).
Distribution: Elliston, S. Aust., to Walkerville, Victoria, mainly in sheltered situations.
Taxonomic notes: An early collection of this species was made from the wreck of the "John Robb", after which it is named.
References: The Marine Benthic Flora of Southern Australia Part IIIC
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. 15 C–F.
Figure 15 enlarge
Fig. 15. A, B. Crouania destriana (A, AD, A65917; B, AD, A49399). A. Branch with tetrasporangia. B. Branch with whorl-branchlets bearing spermatangia. C–F. Crouania robbii (AD, A52115). C. Type specimen. D. Branch with slight cortication and ecorticate lateral, tetrasporangial. E. Older branch with moderate rhizoidal cortication. F. Thallus with a carposporophyte.
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