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Electronic Flora of South Australia Family Fact Sheet
Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae
Thallus small, epiphytic, ecorticate, attached by a single basal cell or a pectinate holdfast, with a curved primary axis, each cell producing unilaterally secondary branches on the convex side, branches irregularly alternately or oppositely branched with some secondary axes branching as the primary axis; terminal cells rounded or becoming hair-like and caducous; gland cells absent. Cells uninucleate.
Reproduction: Gametophytes di oecious (known mainly in Radiathamnion). Carpogonial branches formed on basal cells of short lateral branchlets on lateral branches, with the auxiliary cell fusing with the fertile axial cell and producing three gonimolobes successively. Spermatangia on elongate heads borne mostly in pairs on cells of laterals, with the spermatangia borne directly on the fertile axial cells, or possibly borne directly on short branchlets.
Tetrasporangia borne on small-celled branchlets on lateral branches, sessile, tetrahedrally divided.
Life History triphasic with isomorphic gametophytes and tetrasporophytes.
Taxonomic notes: The Radiathamnieae was based on the monotypic genus Radiathamnion, distinguished by its vegetative morphology with curved main axes bearing unilateral laterals from the convex side, this pattern being repeated in lesser branchings. The genus Ochmapexus, based on Callithamnion minimum Harvey, is here added to the tribe since it has the same basic morphology; sexual reproduction however is not well known (see below). The two genera differ clearly in their hosts, attachment, and in frond details.
References:
GORDON-MILLS, E.M. & KRAFT, G.T. (1981). The morphology of Radiathamnion speleotis gen. et sp. nov., representing a new tribe in the Ceramiaceae (Rhodophyta) from southern Australia. Phycologia 20, 122–130.
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 RADIATHAMNIEAE
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1. Epiphytic in apical pits of Laurencia spp.; attachment by a single basal cell; branchlets alternate on laterals, tapering to hair-like ends | RADIATHAMNION |
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1. Epiphytic on the surface of Caulerpa, Halopteris and occasionally other algae; attachment by a distinctive pectinate multicellular holdfast; branchlets opposite or alternate | OCHMAPEXUS |
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Email Contact: State Herbarium of South Australia |
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