Ceramium clarionense Setch. & N.L.Gardner

Scientific Description

Habit and structure. Thallus primarily erect, to 5 mm tall, light red, attached to the substratum by rhizoids arising from nodal cortical cells associated with lower axial cells. Erect axes subdichotomously branched every 5–7 axial cells, with moderately curved to involute apices. Adventitious branches commonly arising from lower axial cells, these primarily simple and curved towards the plant apex. Axial cells c. 120 µm diam. near apices (including the thick wall that forms a relatively continuous layer over the entire branch), broadening to 310 µm diam. lower down but then with narrower basal cells; most axial cells (excluding the wall) lens-shaped near the apices, becoming subspherical [L:B to 1], with a prominent cytoplasmic thread running between the pit connections. Periaxial cells forming at apices, 7 or 8 per axial cell, then cutting off obliquely laterally pseudoperiaxial cells so that mature nodes have a central irregular ring of c. 16 larger cells. Periaxial and pseudoperiaxial cells cutting off corticating cells equally abaxially and adaxially, forming a nodal cortex of 6–16 irregular rows, the outermost row of angular cells. Hair cells common on the outer cortex.

Reproduction. Spermatangia tufted on outer cortical cells. Tetrasporangia arising from distal cortical cells, initially abaxially but eventually forming complete whorls, occasionally partly exposed but mostly completely covered by cortical cells, subspherical to ellipsoidal, 35–50 µm long, 25–38 µm diam., cruciately divided. Carpogonial branches and cystocarps forming near branch apices, with 1 or 2 subspherical gonimolobes to 280 µm diam., composed of angular carposporangia. Cystocarps subtended by short adventitious branches.

Distribution. Widespread in warmer seas.

Habitat. Epiphytic on various algae.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 395–397 (2018)]