Ceramium aduncum Y.Nakam.

Scientific Description

Habit and structure. Thallus pale red, essentially erect or with a reduced prostrate axis, attached by rhizoids arising from nodal cells. Erect axes to 4 mm tall, dichotomously branched every 8–10 cells, with forcipate apices. Nodal cortication with 8 or 9 periaxial cells, each cutting off 2 acropetal and 2 basipetal cells, these then cutting off several smaller cells both acropetally and basipetally; when mature often covering or forming rosettes around the periaxial cells. Vesicular cells very common, arising from periaxial cells or other nodal cells, at branch apices very prominent along the convex abaxial surface where they are hemispherical and up to 35 µm diam., elsewhere more spherical to ellipsoidal, 20–30 µm long. Mature nodes 150–200 µm diam., 80–100 µm tall; axial cells cylindrical to subspherical, to 200 µm diam. (including a thick wall) [L:B 1–1.5].

Reproduction. Spermatangia covering nodal cells for several distal segments. Tetrasporangia adaxial in longitudinal series, directly on periaxial cells or on an acropetal stalk cell, 1 or 2 per node, pyriform to subspherical, 60–90 µm diam. (including a thick wall), tetrahedrally divided, lacking an involucre. Female gametophytes and carposporophytes not seen.

Distribution. Occurs in warmer waters of the central and western Pacific Ocean; also in the Indian Ocean and Australia.

Habitat. Epiphytic on various algae in the intertidal to shallow subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 387 (2018)]