Anotrichium tenue var. thyrsigerum (Harv.) H.S.Kim & I.K.Lee

Scientific Description

Habit and structure. Thallus dark red, in dense or loose tufts, 1–5 cm high, with procumbent filaments producing erect, subsecund branches adventitiously from the lower ends of cells. Attachment by simple filamentous rhizoids opposite erect filaments or alternate with them, and often ending in much-branched haptera; on seagrasses and larger algae, epilithic or as a short turf mixed with sand. Structure. Cells near the thallus apex urceolate to short-cylindrical, 60–100 µm in diameter and L/D 0.8–0.9, in mid thallus elongate-cylindrical, 160–230 µm in diameter and L/D 2–5(–9) and in the prostrate filaments cylindrical, 180–290 µm in diameter and L/D 1.5–2.5; synchronic hair-like laterals 8–16, arising as 1–2 whorls of papillose protrusions from sub-apical cells, and dividing 1–3 times di-poly-chotomously, greatly elongating and forming distinctive masses of extremely narrow branches with basal cells 10–20 µm in diameter and L/D 12–14, persisting up to 7 axial cells from the apex, but eventually caducous.

Reproduction. Gametophytes dioecious. Female axes 3-celled, subapical, displaced laterally by the continued growth of the vegetative apical cell, not associated with synchronic hair-like laterals; procarp systems subapical, each with a sterile lateral cell abaxially and an adaxial supporting cell bearing a sterile cell apically and a recurved, 4-celled carpogonial branch laterally; hypogenous cell enlarging, becoming pyriform at time of fertilisation, and producing a whorl of 12–13 synchronic, single-celled involucral branches incurved about the developing gonimoblast; post-fertilisation fusion cell columnar, bearing 1–3 gonimolobes terminally, most cells of which form globose carposporangia, 32–45 µm in diameter. Spermatangia borne in whorls of 4–8 pedicellate heads, produced synchronously from upper shoulders of cells near the thallus apex, within whorls of synchronic, hair-like laterals which are readily lost as the heads enlarge; each spermatangial head with a 2(–4) celled fertile axis, and a basal cell elongating to become a clavate pedicel 88–120 µm in diameter and L/D 1.5–2, extending on its abaxial side so that the head is displaced to a slightly subterminal and adaxial position; mature heads globose-ovoid, or lobed if the axial cells elongate, 130–180 µm in diameter, produced from several polychotomous divisions of 4 periaxial cells on each of the axial cells. Tetrasporangia single on whorls of 8–10(–14) clavate pedicels 75–123 µm in diameter and L/D 1.5–2, produced synchronously from the distal shoulders of cells towards the apex of axes, opposite 1–2 whorls of synchronic, hair-like laterals; globose, 65–105 µm in diameter, initially terminal on pedicels but, characteristically for this variety, displaced to a subterminal and adaxial position by the extension of the pedicel abaxially, tetrahedrally divided.

Distribution.Widely distributed in temperate and mixed temperate-tropic waters of southern Africa, the Indian Ocean, southern and eastern Australia, and Hawaii. In southern Australia, Rottnest I., W. Aust., to Newport, N.S.W., apparently absent in the colder waters of Tas.

Habitat. The lower eulittoral to upper sublittoral.

[After Womersley, Mar. Benthic Fl. Southern Australia IIIC: 340–344 (1998)]