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Electronic Flora of South Australia Genus Fact Sheet
Phylum Rhodophyta – Class Florideophyceae – Order Gracilariales – Family Gracilariaceae
Thallus erect, irregularly branched, branches terete or compressed; holdfast discoid, epilithic. Structure uniaxial but central axis not apparent, pseudoparenchymatous with a small-celled. cortex grading to a large-celled medulla, cells with numerous secondary pit-connections.
Reproduction: Gametangial thalli dioecious. Carpogonial branches 2-celled, borne on an inner cortical (supporting) cell which also bears two adjacent filaments, the fertilized carpogonium fusing with cells of these filaments, then producing a dense gonimoblast of relatively small ovoid cells with terminal chains of carposporangia; traversing nutritive cells absent, but lower gonimoblast cells becoming pit-connected to cells in the floor of the cystocarp. Cystocarps prominent, sessile, hemispherical to conical, not or very slightly basally constricted, pericarp thick, ostiolate. Spermatangia scattered, cut off by transverse divisions from surface cortical cells via elongate initials.
Tetrasporangia scattered, basally pit-connected to mid cortical cells, decussately divided.
Life history triphasic with isomorphic gametophytes and tetrasporophytes.
Type species: G. sjoestedtii (Kylin) Dawson (1949, p. 40) [= G. lemanaeformis* (Bory) Dawson, Acleto & Foldvik (1964, p. 59)].
Taxonomic notes: A genus of about 4 species, the type species clarified by Fredericq & Hommersand (1989b) who consider Gracilariopsis generically distinct from Gracilaria rather than a subgenus of the latter. Steentoft et al. (1995) clarify the occurrence of Gracilariopsis longissima and Gracilaria gracilis on coasts of the British Isles.
References:
DAWSON, E.Y. (1949). Studies of Northeast Pacific Gracilariaceae. Allan Hancock Found. Pubis, Occ. Paper 7, pp. 1–105.
FREDERICQ, S. & HOMMERSAND, M.H. (1989b). Comparative morphology and taxonomic status of Gracilariopsis (Gracilariales, Rhodophyta). J. Phycol. 25, 228–241.
STEENTOFT, M., IRVINE, L.M. & FARNHAM, W.F. (1995). Two terete species of Gracilaria and Gracilariopsis (Gracilariales, Rhodophyta) in Britain. Phycologia 34, 113–127.
The Marine Benthic Flora of Southern Australia Part IIIB complete list of references.
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.
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