Electronic Flora of South Australia Family Fact Sheet

FAMILY CAULACANTHACEAE Kützing 1843: 389, 394

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales

Thallus erect or entangled (one genus pulvinate and parasitic), branches terete or compressed. Structure uniaxial or with a small group of apical cells, axial cells with 1 or 2 periaxial cells producing a medulla of either lax periaxial filaments (without rhizoids) or becoming pseudoparenchymatous, with the axial filament distinct throughout or soon inconspicuous, and a pseudoparenchymatous cortex.

Reproduction: Sexual thalli monoecious or dioecious; non-procarpic. Carpogonial branches borne on inner cortical or outer medullary cells, (2–) 3 (–5)-celled, straight and more or less outwardly directed; connecting filaments usually single (often more in Catenella), relatively short, unbranched and non-septate; auxiliary cell a nearby inner cortical cell, producing after diploidization a single inward gonimoblast initial or several outwardly (in Heringia), without adjacent vegetative cells forming nutritive tissue, followed by development of an extensive fusion cell with radial gonimoblast filaments bearing single or short chains of carposporangia. Cystocarps without filamentous enveloping tissue, usually ostiolate. Spermatangia cut-off from outer cortical cells in clusters or rosettes.

Tetrasporangia scattered or in nemathecia, basally attached to inner cortical cells, successively zonately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Taxonomic notes: A family of 7 or 8 genera, with one in southern Australia. The family is not clearly defined, but is characterised by the usually distinct axial filament (not in Catenella) cutting off 1 or 2 periaxial cells, the lack of rhizoids in the medulla, the straight, outwardly directed, carpogonial branches, the lack of nutritive cells adjacent to the auxiliary cell, and the lack of filamentous enveloping tissue. These features contrast with the Areschougiaceae, though several are found in Melanema, which may be better placed in the Caulacanthaceae.

References:

KÜTZING, F.T. (1843). Phycologia generalis. (Leipzig.)

The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.

Author: H.B.S. Womersley

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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