Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Dumontiaceae
Thallus erect, mucilaginous, usually much branched with terete or flattened branches, sometimes with a slight annular appearance. Structure uniaxial, with whorls of 4 (–6) periaxial cells when mature, each producing 2–4 elongate cells for several orders, with the outermost forming a loose to moderately compact cortex bearing floridean but not acicular hairs; descending rhizoids usually developed from medullary cells.
Reproduction: Sexual thalli usually dioecious. Carpogonial and auxiliary cell branches scattered, borne on periaxial or inner medullary cells. Carpogonial branches several cells long, simple or rarely with laterals, straight or terminally reflexed, usually with the carpogonium fusing with cells 4 or 5 of the carpogonial branch, followed by production of several connecting filaments from the fusion cell, each with a basal pit-connection. Auxiliary cell branches of numerous cells (10–20), with the smaller auxiliary cell in the middle or lower half of the branch. Carposporophytes compact, globular, situated within the outer medulla often with ones of different ages intermixed, scarcely swelling the thallus, with all cells becoming carposporangia. Spermatangia cut off in clusters from outer cortical cells.
Tetrasporophytes similar to gametophytes, with large zonately divided tetrasporangia cut off terminally from cells of the outer medulla or inner cortex, or crustose with irregularly cruciately divided tetrasporangia.
Life history triphasic with isomorphic or heteromorphic gametophytes and tetrasporophytes.
Type species: D. coccinea (C. Agardh) Crouan & Crouan 1835: 98 (typ. cons.) [=D. verticillata (Withering) Le Jolis].
Taxonomic notes: A genus of 14 species (Kajimura 1993, p. 47), with the type species from Europe and the other species from the tropical American Atlantic or the Pacific. The single species (D. australis J. Agardh 1899) from southern Australia is one of the earliest described species of the genus. Notoya & Aruga (1989) have clarified the heteromorphic species with a crustose tetrasporophyte.
AGARDH, J.G. (1899). Analecta Algologica. Cont. V. Acta Univ. lund. 35, 1–160, Plates 1–3.
CROUAN, P.L. & CROUAN, H.M. (1835). Observations microscopiques sur la genre Mesogloia Agardh. Ann. Sci. Nat., 2 Sér. Bot., 3, 98–99.
KAJIMURA, M. (1993). Dudresnaya okiensis sp. nov. (Dumontiaceae, Rhodophyta) from the Sea of Japan. Phycologia 32, 40–47.
NOTOYA, M. & ARUGA, Y. (1989). The life history of Dudresnaya japonica Okamura (Cryptonemiales, Rhodophyta) in culture. Jap. J. Phycol. 37, 263–267.
The Marine Benthic Flora of Southern Australia Part IIIA complete list of references.
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.
State Herbarium of South Australia