Galaxaura J.V.Lamouroux, 1812

Lectotype species: Galaxaura rugosa (J.Ellis & Solander) J.V.Lamouroux

Original publication: Lamouroux, [J.V.F.] (1812). Extrait d'un mémoire sur la classification des Polypiers coralligènes non entièrement pierreux. Nouveaux Bulletin des Sciences, par la Société Philomathique de Paris 3: 181-188.

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Type designated in: Schmitz, F. (1889). Systematische Übersicht der bisher bekannten Gattungen der Florideen. Flora oder Allgemeine botanische Zeitung 72: 435-456, pl. XXI.

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Description: Life history triphasic, with gametophytic and tetrasporophytic thalli dimorphic, differing in both gross habit and cortical-cell arrangements. Gametophytic fronds multiaxial, cylindrical, pseudo-dichotomously branched, with or without slightly segmented but non-constricted branches, whereas tetrasporic thalli covered with pigmented epidermal hairs/assimilatory filaments. Primary growth and the morphology of spermatangial conceptacles, procarps and cystocarp are similar to that found in Dichotomaria; however, the multinucleate fusion cell in Galaxaura incorporates more inner proximal gonimoblast cells (7-10) than that seen (3-4) in Dichotomaria. Its primary gonimoblast filaments form a conceptacle, in contrast to that found in Dichotomaria; the involucral filaments derived from the basal cell do not form a pericarp but are restricted to the base throughout the development of the cystocarp (Wang et al., 2005: 691, 692). Plants erect, dichotomously branched; branches terete to flattened, glabrous or covered with photosynthetic hairs, calcified, articulated or non-articulated, multiaxial. Medulla filamentous. Cortical structure gametophytes and tetrasporophytes dimorphic; gametophyte cortex three layered, inner one or two layers of large colorless cells often fused laterally, remaining outer cortex of progressively smaller pigmented cells; cortex of tetrasporophytes either essentially filamentous, with or without inflated basal cells supporting assimilatory filaments, or pseudoparenchymatous, of three to six layers; inner cortex of one to three layers of large colorless cells; cells of the outermost layer borne on smaller pigmented supporting cells with calcification of the gaps between the supporting cells. Monoecious or dioecious. Spermatangia formed in subcortical cavities. Carpogonial branches 3-celled, replacing vegetative filaments. Prior to fertilization the hypogynous cell and basal cell each produce three to four sterile branches, the sterile branches making a minor contribution to the conceptacle wall. Gonimoblast initiated from carpogonium and forming most of the immersed cystocarp wall. Fusion cell formed from carpogonium, hypogynous cell, basal cell and part of conceptacle wall filaments. Carposporangia terminal on gonimoblast filaments that radiate from conceptacle wall toward center of cystocarp. Tetrasporangia cruciately divided, either lateral or terminal on assimilatory filaments, lateral on cells supporting outer cortex, or terminal on outer cortical cells.

Information contributed by: R.B. Searles. The most recent alteration to this page was made on 2017-01-20 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.

Comments: Mostly tropical to subtropical, a few species in temperate waters, low tide line to deep subtidal.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 20 January 2017. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 15 June 2024

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