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Electronic Flora of South Australia Genus Fact Sheet

Genus PREDAEA G. De Toni 1936: [5].

Phylum Rhodophyta – Class Florideophyceae – Order Gigartinales – Family Nemastomataceae

Thallus (gametophytes) mucilaginous, flabellate or variously lobed, compressed, attached by a short stipe and holdfast. Structure of a laxly filamentous medulla with cortical, subdichotomous, branch systems, in some species with longer exserted cortical tufts, without secondary pit-connections.

Reproduction: Sexual thalli monoecious or dioecious. Carpogonial branches usually 3-celled (2–5-celled), borne on inner cortical cells near the basal dichotomy, occasionally elsewhere. Auxiliary cells intercalary near the base of a cortical system, with the adjacent cells above and below (and others in some species) bearing short (1–5-celled) simple or branched chains of subspherical nutritive cellules. Gonimoblast initial arising from auxiliary cell or connecting filament, with most or all cells becoming carposporangia in an ovoid to lobed carposporophyte lying within the cortex; pericarp absent. Spermatangia cut off from outer cortical cells, clustered or digitate, producing subspherical spermatia.

Tetrasporophytes (only known in culture) filamentous, much branched, becoming crustose, with erect filaments producing cruciately or zonately divided tetrasporangia.

Life history (where known) heteromorphic, with crustose tetrasporophytes producing terminal cruciately or zonately divided tetrasporangia and also monosporangia (see Millar & Guiry 1989, p. 418).

Type species: P. masonii (Setchell & Gardner) G. De Toni 1936: [5].

Taxonomic notes: A genus of some 13 species (Millar & Guiry 1989, p. 419), mainly subtropical (Kraft & Abbott 1971, p. 200) with five Australian species (Kraft 1984a), one of which just reaches southern Australia. This species, and an undescribed species (sterile and male plants only from Vivonne Bay, Kangaroo I., and Portsea, Vic.) are characterised by cortical tufts of two lengths, and the undescribed species also has intercalary gland cells.

Predaea is characterised by the presence of small, subspherical, nutritive cells on the cells just above and below the auxiliary cells, in some species on other adjacent cells.


DE TONI, G. (1936). Noterelle de nomenclatura algologica. VII. Primo elenco di Floridée omonime. (Brescia.)

KRAFT, G.T. & ABBOTT, I.A. (1971). Predaea weldii, a new species of Rhodophyta from Hawaii, with an evaluation of the genus. J. Phycol. 7, 194–202.

KRAFT, G.T. (1984a). The red algal genus Predaea (Nemastomataceae, Gigartinales) in Australia. Phycologia 23, 3–20.

MILLAR, A.J.K. & GUIRY, M.D. (1989). Morphology and life history of Predaea kraftiana sp. nov. (Gymnophloeaceae, Rhodophyta) from Australia. Phycologia 28, 409–421.

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

Author: by H.B.S. Womersley & G.T. Kraft

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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