Tanakaella itonoi Huisman & Gordon-Mills

Scientific Description

Habit and structure. Thallus red-brown, 1–5 mm high, forming small erect tufts, subdichotomously branched, from prostrate basal filaments. Attachment by branched haptera; epiphytic on Kallymenia cribrosa and Thamnophyllis lacerata. Structure. Apical cells 8–15 µm in diameter and L/D 6–15, dividing transversely, median and basal cells (20–)40–100 µm in diameter and L/D 4–10. Cells multinucleate; rhodoplasts discoid.

Reproduction. Propagules borne laterally on upper cells, single celled, ovoid, 55–90 µm in diameter, with a single small discoid basal cell. Gametophytes dioecious. Procarps borne on the subapical cell of short axes, with 3 periaxial cells, one acting as the supporting cell and bearing a carpogonial branch and a sterile cell; hypogenous cell larger, with a lateral vegetative branch. Post-fertilization only the supporting cell cuts off an auxiliary cell, which produces 3 successive gonimolobes 80–220 µm across, with isodiametric carposporangia 20–25 µm across. The involucral groups around the carposporophyte, and loose outer involucral filaments develop from cells below the fertile axis. Spermatangial heads are borne on upper adaxial ends of median thallus cells, ovoid, 30–45 µm in diameter. Tetrasporangia borne on upper ends of axial cells, subspherical to slightly ovoid, 20–30 µm in diameter, tetrahedrally divided.

Distribution.Houtman Abrolhos and Rottnest I., W. Aust.; Egg I., Isles of St Francis to Troubridge I., S. Aust.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 310–312 (1998)]