Giraudyopsis P.J.L.Dangeard, 1965, nom. inval.

Holotype species: Giraudyopsis stellifer P.J.L.Dangeard

Original publication and holotype designation: Dangeard, P.[J.L.] (1965). Sur un nouveau genre de Phéophycées: Giraudyopsis nov. gen. (G. stellifer). Compte Rendu Hebdomadaire des Séances de l'Académie des Sciences. Paris. 261: 2699-2701, 2 pls [I, II].

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Description: Thallus filamentous, appearing as small rosettes (300-400 µm in diam.), with erect filaments radiating from a central, irregular, prostrate disc. Filaments uniseriate (6-8 µm in diam.) with quadrangular cells, becoming partially or totally pluriseriate following longitudinal divisions. Branching irregular and infrequent. One brown parietal chloroplast with a membrane-limited embedded pyrenoid, visible in thin-sections only. Chrysolaminaran vacuoles and lipid droplets present. Individual cell-walls thin, filament envelope thick. Zoospores formed singly from vegetative cells of pluriseriate filaments, with no morphologically distinct sporangia. Zoospores small, pyriform (3-5 x 5-7 µm), with 2, lateral, strongly unequal heterokont flagella (4 and 15 µm). The long anterior flagellum bears tripartite mastigonemes, while the short posterior flagellum is acronematic. Zoospores negatively phototactic, with one chloroplast bearing a stigma. No stomatocysts nor sexual reproduction observed. Extracellular calcified pseudocysts, similar to those of Chrysowaernella, have been recorded (Gayral and Haas, 1969).

Information kindly contributed by C. Billard & M.D. Guiry but may now be outdated.

Taxonomic status: The taxonomic or nomenclatural status (or both) of this entity is in some way unresolved and requires further investigation.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Kawai, H. & Nakayama, T. (2015). Introduction (Heterokontobionta p.p.), Cryptophyta, Dinophyta, Haptophyta, Heterokontophyta (except Coscinodiscophyceae, Mediophyceae, Fragilariophyceae, Bacillariophyceae, Phaeophyceae, Eustigmatophyceae), Chlorarachniophyta, Euglenophyta. In: Syllabus of plant families. Adolf Engler's Syllabus der Pflanzenfamilien. Ed. 13. Phototrophic eukaryotic Algae. Glaucocystophyta, Cryptophyta, Dinophyta/Dinozoa, Haptophyta, Heterokontophyta/Ochrophyta, Chlorarachnniophyta/Cercozoa, Chlorophyta, Streptophyta p.p. (Frey, W. Eds), pp. 11-64, 103-139. Stuttgart: Borntraeger Science Publishers.

Comments: The type G. stellifer P.J.L. Dangeard, is a microscopic, marine epiphyte, growing on various Phaeophyceae. Although rarely recorded, the type appears of cosmopolitan distribution (Billard, 1988). Considered by its author to be a member of the Phaeophyceae (Dangeard, 1965), subsequent morphological and ultrastructural investigations (Loiseaux, 1967; Billard, 1974; O'Kelly and Floyd, 1985), and biochemical studies (Billard and others, 1990) have indicated that Giraudyopsis is not a brown alga. Recent analyses of molecular data (Saunders et al., 1997) have been unable to resolve its true phylogenetic affinities.

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Contributors
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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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 20 December 2023. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 25 April 2024