Claudea elegans J.V.Lamour.

Scientific Description

Habit and structure. Thallus rose-red to grey-red, (10–)20–40 cm high, with several axes usually basally branched and becoming 2–3 mm thick basally. Axes with upper net-like fronds usually 5–15 cm long and 1–3 cm broad, tapering apically, unilaterally placed on narrow "mid-ribs" with membranous wings opposite the nets and rectangular interstices; apices of fronds usually curved abaxially, with frond margins dentate due to the apices of second-order filaments; axes becoming thickened and denuded below. Holdfast discoid, formed of spreading rhizoids, becoming pseudoparenchymatous; epilithic or on shells. Structure. Apical cells of blades dome-shaped, segmenting after 4–7 cells to form first 2 lateral pericentral cells, followed by lower (abaxial) and upper (adaxial) transverse pericentral cells. The lateral pericentral cells cut off 2 flanking cells, the upper (anterior) one forming a second-order row with most of the inner cells forming third-order rows; the lower (posterior) flanking cell develops as an unbranched third-order row also. Short fourth-order rows may develop from cells near the margin, and all rows reach the thallus margin. The wings developed from the lateral pericentral cells become 1–2 mm and many cells broad on the primary axes. The upper (adaxial) transverse pericentral cells produce secondary blades from successive segments, branched as above but smaller, lying in a plane at right angles to the parent blade, 80–120 µm and 6–10 cells broad. These secondary blades produce filaments (4–)6–10 cells long from the upper transverse pericentral cells which extend to and unite with the lower (abaxial) transverse pericentral cells of the secondary blade above them. As the frond expands, these filaments develop into tertiary blades (with their apical cell adherent above) which repeat the blade development. Apices of the secondary blades project as the dentations on the frond margins. Cortication of the midrib and lateral cells of primary blades commences some distance below the apices and becomes relatively thick below as the wings and blades are lost from older parts. Cells mostly multinucleate; rhodoplasts discoid.

Reproduction. Gametophytes dioecious. Procarps borne in series on the lower (abaxial) side of primary and secondary blades close to apices, without development of the next order of branches near the procarps. The abaxial pericentral cell becomes the supporting cell, cutting off two sterile groups and a 4-celled carpogonial branch. Carposporophyte with a basal fusion cell, much branched gonimoblast with broadly clavate to ovoid terminal carposporangia 50–90 µm in diameter, replaced from subterminal cells. Cystocarps on slender stalks 2–5 mm long, single or in small clusters of adjacent stalks developed from the midrib and narrow wings, ovoid, 1–2 mm in diameter, with a slight neck only. Pericarp with an outer cortical layer of irregular but closely adjacent cells. Spermatangial sori covering tertiary and quaternary blades of the nets, derived from lateral pericentral cells and inner cells of second and third-order rows, leaving the transverse pericentral cells and marginal (often also submarginal) cells sterile, with the primary cells dividing anticlinally and cutting off initials which each produce several spermatangia. Tetrasporangial stichidia developed from tertiary branches of the nets (which then lack further branches); the lateral pericentral cells form only a single second-order row of elongate cells, apart from division into 2 flanking cells (and later more third-order rows) at the margins. Stichidia ovate, 1–1.5 mm long and 500–700 µm broad, with the tetrasporangia cut off from 3–5 cells of the single rows from the lateral pericentral cells, essentially in a single layer but usually pushed into 2 layers, with occasional further tetrasporangia cut off from the primary cells; the oldest tetrasporangia are situated centrally in the sorus (both longitudinally and near the midrib) and are subspherical, 50–120 µm in diameter.

Distribution. Fremantle, W. Aust., to Walkerville, Vic., and N Tas.

Habitat. C. elegans is generally epilithic in the subtidal.

[After Womersley, Mar. Benthic Fl. Southern Australia IIID: 16–20 (2003)]