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Genus GLOIOCLADIA J. Agardh 1842: 87

Phylum Rhodophyta – Class Florideophyceae – Order Rhodymeniales – Family Rhodymeniaceae

Thallus erect, mucilaginous, much branched radially or complanately, main branches subdichotomous or pinnate, branches terete and flanged, or compressed, thallus attached by discoid holdfasts. Structure multiaxial, solid, with a cortex of anticlinal branched filaments of slender cells with the inner cells forming a reticulum, and a medulla of large ovoid cells with numerous secondary pit-connections and often rhizoidal filaments between the larger cells.

Reproduction: Gametangial thalli monoecious or dioecious. Carpogonial branches borne on relatively large supporting cells in the inner cortex, 2- or 3-celled, together with 2-celled auxiliary cell branches, the auxiliary cell usually with a globular proteinaceous inclusion. Carposporophyte erect, with a basal, often branched, fusion cell bearing lobes with all cells becoming carposporangia. The supporting cell and the basal cell of the auxiliary cell branch have prominent pit-connections to rows of cells, the lower ones remaining short and darkly staining as the nutritive tissue, the erect cells prominent and elongate with frequent lateral connections but persistent as they are stretched by the developing carposporophyte, and the upper cells remaining short in filaments that surround the ostiole. Cystocarps external, mainly marginal on flat branches, pericarp relatively thick and usually with 1–4 prominent horns. Spermatangia cut off from surface cortical cells.

Tetrasporangia scattered or in sori or nemathecia, pit-connected to mid cortical cells, ovoid-elongate, decussately divided.

Life history triphasic, with isomorphic gametophytes and tetrasporophytes.

Type species: G. furcata J. Agardh 1842: 87.

Taxonomic notes: Doubts concerning the separation of Gloiocladia J. Agardh (1842, p. 87) and Gloioderma J. Agardh (1851, p. 243) [and Fauchea Montagne & Bory] were expressed by Irvine & Guiry (1986, pp. 289–291), following earlier comments by Sparling (1957). Irvine & Guiry refrained from uniting these genera in view of the lack of information on the type species of Gloiocladia, especially of the female reproduction and cystocarp structure. Norris (1991, p. 592) however, concluded they were generically the same and transferred most of the names used in Gloioderma to Gloiocladia. Study of cystocarpic and tetrasporangial plants of Gloiocladia furcata from Ile Lavezzi, Corsica, 37 m deep (M. Verlaque, 30.xi.1989; Herb. LBMEB, No. 112538; AD, A64305) show that although a much smaller species than the Australian species placed in Gloioderma, they are very similar in structure, cystocarp structure (with basal nutritive tissue and persistent erect filaments around the carposporophyte - Fig. 34D) and tetrasporangial nemathecia (Fig. 34E, F). The four Australian species are therefore placed under Gloiocladia.


AGARDH, J.G. (1842). Algae Maris Mediterranei et Adriatici, Observationes in Diagnosin Specierum et Dispositionem Generum. (Fortin, Masson: Paris.)

AGARDH, J.G. (1851). Species Genera et Ordines Algarum. Vol. 2, Part 1, I-XII, 1–336 + index. (Gleerup: Lund.)

IRVINE, D.E.G. & GUIRY, M.D. (1986). Taxonomy of the Rhodyméniales. In T.V. Desikachary (Ed.). Taxonomy of Algae, pp. 287–303, Plates 1, 2. (Univ. Madras: Madras.)

NORRIS, R.E. (1991). Some unusual marine red algae (Rhodophyta) from South Africa. Phycologia 30, 582–596.

SPARLING, S.R. (1957). The structure and reproduction of some members of the Rhodymeniaceae. Univ. Calif Pubis Bot. 29, 319–396.

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

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (28 June, 1996)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIB. Gracilarialse, Rhodymeniales, Corallinales and Bonnemaisoniales
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIIB 1996, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus branches terete to flanged, 1–2 mm broad, mainly radially branched

G. fruticulosa

1. Thallus branches strongly compressed to flat, mostly 4–10 mm broad, complanately and marginally branched


2. Thallus largely subdichotomously branched, 5–10 (–15) mm broad, often developing surface (1–5 mm long) and marginal (mostly 0.5–2 cm long) proliferations, especially on lower parts

G. polycarpa

2. Thallus pinnately branched for 1–3 orders, usually without numerous surface proliferations


3. Thallus irregularly pinnate, soft and mucilaginous, with discoid adhesive appendages on the ends of some branchlets; usually epiphytic on sea-grasses

G. australe

3. Thallus regularly pinnate, tapering to branch apices, without discoid, adhesive appendages; usually epilithic

G. halymenioides

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