Electronic Flora of South Australia Genus Fact Sheet

Genus THAMNOCLONIUM Kützing 1843: 392

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Halymeniaceae

Thallus much branched irregularly to subdichotomously, branches terete to compressed, covered throughout with short, irregularly branched excrescences and coated with a thin layer of sponge, attached by a discoid-conical holdfast. Structure of branches and excrescences of a pseudoparenchymatous cortex and a compact filamentous medulla, with a thick secondary cortex with numerous growth rings developing below.

Reproduction: Reproductive structures borne in special small fertile leaflets (lacking sponge cover) clustered at the branch apices or laterally, with a relatively lax filamentous medulla.

Sexual thalli dioecious. Carpogonial branch ampullae arising in inner cortex, with a few short, erect filaments and a 2-celled carpogonial branch. Auxiliary cell ampullae with numerous secondary filaments of elongate cells, slightly converging above, developing more lateral filaments post-fertilization. Carposporophytes crowded, involucre prominent, developed from branched ampullary filaments; a narrow ostiole present. Spermatangia cut off from outer cortical cells.

Tetrasporangia in nemathecia on fertile leaflets, cut off from subsurface cells and with a thicker cortex developing, cruciately divided.

Life history triphasic with isomorphic gametophytes and tetrasporophytes.

Type species: T. hirsutum Kützing 1843: 392 [= T. dichotomum (J. Agardh) J. Agardh].

Taxonomic notes: A genus of about five species (Scott, Wetherbee & Kraft 1984, p. 288) with one species (with several synonyms) common on southern Australian coasts and a second species (T.

lemannianum Harvey) from south-western Western Australia but not extending to southern Australia. Another species occurs in South Africa and three little known species are credited to Indonesia (Weber-van Bosse 1921, p. 250).

References:

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

SCOTT, F.J., WETHERBEE, R. & KRAFT, G.T. (1984). The morphology and development of some prominently stalked southern Australian Halymeniaceae (Cryptonemiales, Rhodophyta). B. The sponge-associated genera Thamnoclonium Kützing and Codiophyllum Gray. J. Phycol. 20, 286–295.

WEBER-VAN BOSSE, A. (1921). Liste des Algues du Siboga. II. Rhodophyceae. Part I. Protoflorideae, Némalionales, Cryptonemiales. Siboga-Expeditae, Monogr. Lab, pp. 187–310, Plates 6–8.

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

Author: H.B.S. Womersley & J.A. Lewis

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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