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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Caulacanthaceae
Thallus clumped or entangled, branches segmented with elongate-ovoid internodes and constricted nodes, branching from the distal ends of internodes, segments terete to compressed, attached by numerous haptera; epilithic or on wood or mangroves. Structure uniaxial or with a small group of apical cells producing several similar axial filaments, each cell with 1 or 2 periaxial cells, and a lax reticulate medulla, with a cortex 2–5 cells thick.
Reproduction: Sexual thalli dioecious; non-procarpic. Carpogonial branches (2–) 3 (–5)-celled, sometimes with sterile cells on the basal cell, borne on inner cortical or outer to mid medullary cells, relatively straight and outwardly directed, producing 1–2 connecting filaments. Auxiliary cell an inner cortical or outer to mid medullary cell, producing a gonimoblast initial more or less inwardly and forming a fusion cell with radial gonimoblasts with chains of ovoid carposporangia. Cystocarps swelling the branchlets and becoming stipitate, without filamentous enveloping tissue and with the cortex only slightly thickened, more or less ostiolate. Spermatangia scattered, cut off from outer cortical cells.
Tetrasporangia scattered, usually densely, in the outer cortex, laterally attached, zonately divided.
Life history triphasic with isomorphic gametophytes and tetrasporophytes.
Type species: C. opuntia (Goodenough & Woodward) Greville 1830: lxiii, 166. C.
caespitosa (Withering) Irvine in Parke & Dixon 1976: 590].
Taxonomic notes: A genus of 5 species mainly in the tropics and subtropics and often associated with mangroves. One species reaches southern Australia.
Characterised by the elongate-ovoid segments with haptera on many segments, the small group of one to a few apical cells giving several similar axial filaments, and the chains of carposporangia from the irregular fusion cell.
References:
GREVILLE, R.K. (1830). Algae Britannicae. (Maclachlan & Stewart: Edinburgh.)
PARKE, M. & DIXON, P.S. (1976). Check-list of British marine algae - third revision. J. mar. biol. Ass. U.K. 56, 527–594.
The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.
Publication:
Womersley, H.B.S. (14 January, 1994)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIA, Bangiophyceae and Florideophyceae (to Gigartinales)
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIA 1994, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.
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