Ceramium cliftonianum J.Agardh

Scientific Description

Habit and structure. Thallus light to dark red, forming erect, often much branched or entangled tufts from 3 mm to 10(–15) cm high, with prostrate branches; branching in actively growing erect parts subcomplanate with fairly regular laterals usually 3–6 cells apart with broad axils, but often more irregular and sparse, commonly with older branches bearing proliferous laterals which are often markedly slenderer. Attachment by uniseriate rhizoids with pads becoming multicellular, 1–3 rhizoids arising from the periaxial cells at each node; epilithic or on other firm substrates (e.g. tunicates) or epiphytic. Structure. Branches 100–300(–400) µm in diameter below, tapering gradually or more abruptly to (25–)50–75(–100) µm in diameter below the tapering apices, which are straight or occasionally slightly involute or divergent. Axial cells L/D about 1 near the apices, elongating to 2–3(–4) below, with clear internodal spaces throughout. Periaxial cells usually 6, each first cutting off 2 cells acropetally and usually soon after 2 cells basipetally; acropetal cortical cells usually each cutting off 1 or 2 smaller cells, giving a node 4 cells and 30–50 µm long in the upper parts; on older, lower, branches further acropetal cells, and sometimes basipetal ones, may be cut off, giving a node 5–6(–9) cells and 75–125 µm long, with the acropetal development always greater (and usually with smaller cells) than the basipetal; internodal space 0.5–1 times the nodal length in upper parts, and 1–3(–4) times as long in lower parts of the thallus. On lower branches, occasional small cortical cells may be cut off in the reverse direction, and in some robust specimens a slight outer cortex may develop on the oldest parts; slender hairs commonly present on cortical cells near branch apices. Rhodoplasts discoid in smaller cells, ribbon like and longitudinal in axial cells.

Reproduction. Gametophytes dioecious. Carposporophytes on upper branches, globular, 150–250(–300) µm across, with 1–4 slightly curved involucral branchlets, carposporangia ovoid-angular, 20–30 µm across. Spermatangia covering cortical cells of upper nodes, sometimes largely restricted to the adaxial sides. Tetrasporangia in unilateral, abaxial series, 1–3 per node, cut off from one (or 2) periaxial cells, involucrate over their lower half or less by branched acropetal cortical filaments 3–4 cells long from the periaxial cells, with the involucral cells lying in the outer part of the common gelatinous sheath with the tetrasporangia centrally situated; tetrasporangia subspherical to ovoid, 35–50(–75) µm across, tetrahedrally (rarely decussately) divided.

Distribution. From Houtman Abrolhos, W. Aust., to Port Stephens, N.S.W., and around Tas.

Habitat. C. cliftonianum is a moderately common species along southern Australia, from 1–35 m depth, occurring as tufts or often entangled masses of slender filaments, in moderate water movement.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 415–416 (1998)]