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Electronic Flora of South Australia Family Fact Sheet
Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae
Thallus much branched radially or distichously with a single lateral from each axial or branch cell (except for involucral branchlets from 1–2 cells below the carposporophyte), with determinate, branched, lateral branchlets which may develop into indeterminate laterals; apical cells inconspicuous or clear, dividing transversely; cortication absent or of appressed filaments within or external to the axial cell wall, or of loose rhizoids, with or without a hirsute outer layer of anticlinally orientated filaments; gland cells absent; cells uninucleate or multinucleate.
Reproduction: Gametophytes usually dioecious, occasionally monoecious. Procarps on intercalary vegetative cells below the branch apices, single or in series a few cells apart, with two opposite periaxial cells, one (the supporting cell) cutting off the 4-celled carpogonial branch. Post-fertilization each periaxial cell cuts off an auxiliary cell and diploid nuclei from the fertilized carpogonium are transferred to each auxiliary cell which divides to form a chain of 3–4 cells, the upper of which develops rounded or furcate-lobed gonimolobes which appear twinned on the branchlets; sterile involucral filaments from cells below the procarp are present or absent. Spermatangial filaments occur on cells of the determinate lateral branchlets, forming one or a few small clusters on each cell, usually adaxial but often spreading around the cell; in some genera forming spermatangial heads.
Tetrasporangia (rarely octosporangia) sessile or pedicellate on cells of the determinate lateral branchlets, usually adaxial, tetrahedrally divided.
Life history triphasic with isomorphic gametophytes and tetrasporophytes.
Taxonomic notes: The Callithamnieae now includes 5 or 6 genera (Millar 1990, p. 403), of which Callithamnion (with multinucleate cells), from which Aglaothamnion (with uninucleate cells) is sometimes separated, Carpothamnion (see Wollaston 1992), and the new genus Hirsutithallia described below, are represented in southern Australia. The separation of the first two genera on the basis of number of nuclei per cell is accepted by some authors (eg. Maggs & Hommersand 1993), but is not followed here since there appear to be no other morphological characters correlated with this.
The tribe is characterised by the position of procarps on intercalary vegetative cells, with two opposite periaxial (and auxiliary) cells which produce two ("twinned") carposporophytes.
References:
MAGGS, C.A. & HOMMERSAND, M.H. (1993). Seaweeds of the British Isles. Vol. 1. Rhodophyta. Part 3A, Ceramiales. (HMSO: London.)
MILLAR, A.J.K. (1990). Marine red algae of the Coffs Harbour region, northern New South Wales. Aust. Syst. Bot. 3, 293–593.
SCHMITZ, F. (1889). Systematische Ubersicht der bisher bekannten Gattungen der Florideen. Flora, Jena 72, 435–456, Plate 21.
WOLLASTON, E.M. (1992). Morphology and taxonomy of Thamnocarpus (Ceramiaceae, Rhodophyta) in southern Australia and east Africa. Phycologia 31, 138–146.
The Marine Benthic Flora of Southern Australia Part IIIC complete list of references.
Publication:
Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia
KEY TO GENERA OF CALLITHAMNIEAE
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1. Branches ecorticate or with a slight cortex on lower axes of loose rhizoids or a thin layer of appressed filaments within the axial cell wall | CALLITHAMNION |
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1. Branches moderately to heavily corticate from near the apices, cortex thick and pseudoparenchymatous or with an outer cortex of moderate to dense anticlinal, short, simple or branched filaments | 2 |
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2. Lower branches with an appressed rhizoidal cortex producing an outer cortical tomentum of short anticlinal filaments | HIRSUTITHALLIA |
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2. Cortex dense and thick from close to apices, of entwined rhizoids becoming pseudoparenchymatous, surrounding a large celled axial filament | CARPOTHAMNION |
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