Gracilaria secundata, copyright Wayne Martin.

Belongs within: Florideophycidae.

The Gracilariales are an order of red algae characterised by the absence of an auxiliary cell.

Characters (from Womersley 1996): Thallus usually erect, branches terete to flat, radially or complanately branched; or parasitic and forming hemispherical pustules. Growth usually multiaxial (or uniaxial, but without an apparent central axis), pseudoparenchymatous, with a small-celled cortex grading to a large-celled medulla, with numerous secondary pit-connections. Apical and outer cortical cells dividing by oblique, longitudinal, concavo-convex walls followed by oblique or transverse division of the subterminal cell, with or without an apical cap of smaller cells. Cell walls containing agar; pit-plugs with one cap layer. Gametangial thalli usually dioecious; auxiliary cells absent. Carpogonial branches 2-celled, outwardly directed from an intercalary mid cortical multinucleate supporting cell which also bears two or more sterile branches; hypogynous cell binucleate to multinucleate, carpogonium uninucleate with a straight trichogyne. Auxiliary cells absent, cells of the sterile branches fusing with the fertilized carpogonium which forms a fusion cell developing laterally and outwardly multiple gonimoblast initials which establish secondary fusions with gametophytic cells in the cystocarp floor and the pericarp, then produce a dense, erect, tuft of filaments surmounted with chains or clusters of subspherical to ovoid carposporangia. Cystocarps protruding, hemispherical, with a thick walled ostiolate pericarp, or as slight bulges in pustular taxa. Spermatangia forming a surface layer or borne in conceptacle-like depressions or cavities. Tetrasporangia (or bisporangia) scattered in the outer cortex or within a shallow nemathecium, cruciately divided. Life history triphasic with isomorphic gametophytes and tetrasporophytes.

    |  i. s.: MelanthaliaSK02
    |           |--M. abscissa (Turner) Hooker & Harvey 1845L27
    |           `--M. obtusataSK02
         |    |--G. lemaneiformisHSA03
         |    |--G. longissimaC03 [incl. Fucus verrucosus (nom. rej.)C03, Gracilaria verrucosa (Hudson) Papenfuss 1950C03, S57]
         |    |--G. pulvinataBS-L99
         |    `--G. sjoestedtii (Kylin) Dawson 1949 [=Gracilaria sjoestedtii]S57
         |--Hydropuntia urvillei Montagne 1842HS14
              |--G. arcuata Zanardini 1858HS14
              |--G. canaliculata Sonder 1871HS14
              |--G. changiiC-SCL15
              |--G. comosaAL04
              |--G. compressa [=G. (Ceramianthemum) compressa]G64
              |--G. confervoides (Linnaeus) Greville 1830L27 [=G. (Plocaria) confervoidesG64]
              |--G. coronopifoliaCH97
              |--G. dura (Agardh) Agardh 1852L27
              |--G. edulis (Gmelin) Silva 1952HS14
              |--G. flagellifera Agardh 1876L27
              |--G. gracilisC03
              |--G. harveyana Agardh 1885L27
              |--G. lemaneiformisAM03
              |--G. lichenoides (Linnaeus) Harvey 1844L27
              |--G. multipartita (Clem.) Agardh 1852L27 [=G. (Podeum) multipartitaG64]
              |    |--G. m. var. multipartitaL27
              |    `--G. m. var. polycarpaL27
              |--G. polycarpa (Harvey) Agardh 1901L27
              |--G. ramulosa Agardh 1876L27
              |--G. salicornis (Agardh) Dawson 1954HS14
              |--G. secundata Harvey 1863L27
              |--G. tenuistipitataJLG03
              |--G. textorii (Suringar) De Toni 1895HS14
              |--G. tikvahiaeSK02
              |--G. vieillardii Silva 1987HS14
              `--G. vivesii Howe 1911N10

*Type species of generic name indicated


[AM03] Arkush, K. D., L. Mendoza, M. A. Adkison & R. P. Hedrick. 2003. Observations on the life stages of Sphaerothecum destruens n. g., n. sp., a mesomycetozoean fish pathogen formally referred to as the rosette agent. Journal of Eukaryotic Microbiology 50 (6): 430–438.

[AL04] Astill, H. L., & P. S. Lavery. 2004. Distribution and abundance of benthic macroalgae in the Swan-Canning Estuary, south-western Australia. Journal of the Royal Society of Western Australia 87 (1): 9–14.

[BS-L99] Burger, G., D. Saint-Louis, M. W. Gray & B. F. Lang. 1999. Complete sequence of the mitochondrial DNA of the red alga Porphyra purpurea: cyanobacterial introns and shared ancestry of red and green algae. Plant Cell 11: 1675–1694.

[CH97] Castro, P., & M. E. Huber. 1997. Marine Biology 2nd ed. WCB McGraw-Hill: Boston.

[C-SCL15] Cavalier-Smith, T., E. E. Chao & R. Lewis. 2015. Multiple origins of Heliozoa from flagellate ancestors: new cryptist subphylum Corbihelia, superclass Corbistoma, and monophyly of Haptista, Cryptista, Hacrobia and Chromista. Molecular Phylogenetics and Evolution 93: 331–362.

[C03] Compère, P. 2003. Report of the Committee for Algae: 7. Taxon 52: 339–340.

[G64] Gray, J. E. 1864. Handbook of British Water-weeds or Algae. R. Hardwicke: London.

[HS14] Huisman, J. M., & A. Sampey. 2014. Kimberley marine biota. Historical data: marine plants. Records of the Western Australian Museum Supplement 84: 45–67.

[HSA03] Huisman, J. M., A. R. Sherwood & I. A. Abbott. 2003. Morphology, reproduction, and the 18S rRNA gene sequence of Pihiella liagoraciphila gen. et sp. nov. (Rhodophyta), the so-called ‘monosporangial discs’ associated with members of the Liagoraceae (Rhodophyta), and proposal of the Pihiellales ord. nov. Journal of Phycology 39: 978–987.

[JLG03] Jacobsen, S., K. Lüning & F. Goulard. 2003. Circadian changes in relative abundance of two photosynthetic transcripts in the marine macroalga Kappaphycus alvarezii (Rhodophyta). Journal of Phycology 39: 888–896.

[L27] Laing, R. M. 1927. A reference list of New Zealand marine algae. Transactions and Proceedings of the New Zealand Institute 57: 126–185.

[N10] Norris, J. N. 2010. Marine algae of the northern Gulf of California: Chlorophyta and Phaeophyceae. Smithsonian Contributions to Botany 94: 1–276.

[SK02] Saunders, G. W., & G. T. Kraft. 2002. Two new Australian species of Predaea (Nemastomataceae, Rhodophyta) with taxonomic recommendations for an expanded Nemastomatales and expanded Halymeniales. Journal of Phycology 38: 1245–1260.

[S57] Scagel, R. F. 1957. An annotated list of the marine algae of British Columbia and northern Washington (including keys to genera). National Museum of Canada Bulletin 150: 1–289.

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