Spirocladia loochooensis (Yendo) T.Yoshida

Scientific Description

Habit and structure. Thallus pale red to brownish red, to 4 cm tall, mostly erect but arising from a network of decumbent axes attached to the substratum at multiple points, generally with percurrent axes bearing lateral branches every 12–25 segments, with occasional adventitious branches. All axes with persistent pigmented trichoblasts arising 1 per segment in a spiral sequence. Primary axes 350–700 µm diam. near the base [segment L:B c. 0.5], tapering gradually to 50 µm diam. [segment L:B c. 0.8–1] below the pointed apices. Trichoblasts proximally 3–6 times alternately or subdichotomously branched from every cell; ultimate branches to 15 cells long, with elongate cells 7–15 µm diam. [L:B 10–25]; terminal cell with a rounded tip. Mature axes mostly ecorticate, becoming lightly corticated in proximal regions by descending rhizoidal filaments arising from pericentral cells.

Reproduction. Spermatangial trichoblasts to 2 mm long, monosiphonous, with a percurrent filament bearing a simple lateral filament from each cell (in sterile and fertile regions), basally with 8 or 9 sterile cells, then with 15–30 cells densely covered by whorled determinate filaments bearing terminal spermatangia, then distally with a short sterile region. Spermatangial region 0.6–1.1 mm long, 100–110 µm wide, tapering distally, with elongate spermatangia 5–7 µm long, 2–3 µm diam. Female fertile trichoblasts with a polysiphonous basal cell and procarps arising laterally on the suprabasal cell. Cystocarps lateral, arising singly or in groups of 2 or 3 on successive segments, urceolate, 500–680 µm diam., with a corticated pedicel and persistent trichoblast arising from the junction of the pedicel and the base of the pericarp. Carposporangia lachrymiform, 75–110 µm long, 25–35 µm wide when mature. Tetrasporangia in trichoblast stichidia similar to spermatangia, basally with 5–8 sterile cells, the fertile region elongate, 480–580 µm long and c. 100 µm diam., with sporangia 1 per segment in a spiral sequence. Sporangia tetrahedrally divided, spherical, 50–85 µm diam.

Distribution. Known from Japan and north-western Australia.

Habitat. epilithic or epiphytic in the subtidal.

[After J.M. Huisman in Algae of Australia: Marine Benthic Algae of North-western Australia, 2. Red Algae: 574–576 (2018)]