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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Family Delesseriaceae
Thallus turf-like or within turf, with prostrate, ecorticate, terete axes attached by uniseriate rhizoids, producing short assurgent indeterminate branches 1–4 mm high bearing determinate laterals with 1–5 persistent apical hairs. Determinate laterals flat, with the lateral pericentral cells each producing 2 flanking cells which remain undivided or form short 2–3-celled chains. Structure. Apical cells of prostrate axes dome-shaped, segmenting to axial cells with 4 pericentral cells; erect branches monopodial with exogenous branching, when mature bearing basally meristematic apical hairs in pit-connection with the axial cells.
Reproduction: Gametophytes rare, usually dioecious. Procarps produced on indeterminate axes, with a pericentral (supporting) cell bearing a 4-celled carpogonial branch and 2 sterile groups. Carposporophyte with a basal fusion cell and short chains of ovoid carposporangia, surrounded by an urceolate pericarp of erect filaments with outer pericentral cells and usually cortical cells on the lower pericarp. Spermatangia formed in sori on both sides of slightly broader flat determinate blades, with the primary cells cutting off initials which produce spermatangia.
Tetrasporangia produced on determinate laterals in 2 rows, from the lateral pericentral cells which each cut off 2 post-sporangial cover cells; tetrasporangia subspherical, tetrahedrally divided.
Type species: T. perpusillum (J. Agardh) J. Agardh 1863: 1257.
Taxonomic notes: A genus of 3 species, the type with 3 monosiphonous apical filaments on the determinate branches, T. nanum (Kützing) Papenfuss (1952, p. 179) with 2 such filaments, recorded from Queensland by Cribb (1983, p. 100), and T. dotyi Hollenberg (1967b, p. 1202, fig. 4) from the Hawaiian Islands, which differs in that the flanking cells form chains of 2–3 cells and there are (3–) 4–5 apical filaments. Some authors (e.g. Hollenberg 1967b, p. 1203) suggest that T. nanum is only a variant of the type species.
References:
AGARDH, J.G. (1863). Species Genera et Ordines Algarum. Vol. 2, Part 3, pp. 787–1291. (Gleerup: Lund.)
CRIBB, A.B. (1983). Marine algae of the southern Great Barrier Reef—Part I. Rhodophyta. (Aust. Coral Reef Soc., Handbook 2: Brisbane.)
HOLLENBERG, G.J. (1967b). New marine algae from the central tropical Pacific Ocean. Amer. J. Bot. 54, 1198–1203.
PAPENFUSS, G.F. (1952). Notes on South African marine algae III. J. S. Afr. Bot. 17, 167–188.
The Marine Benthic Flora of Southern Australia Part IIID complete list of references.
Publication:
Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.
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