Dictyosphaeria Decaisne, 1842

Holotype species: Dictyosphaeria cavernosa (Forsskål) Børgesen

Original publication and holotype designation: Decaisne, J. (1842). Essais sur une classification des algues et des polypiers calcifères de Lamouroux. Annales des Sciences Naturelles, Botanique, Seconde Série 17: 297-380, [pls 14-17].

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Description: Thallus composed of pseudoparenchymatous cushion of polygonal cells; monostromatic or polystromatic; solid or button shaped, 1-5 cm, or hollow and spherical or cup shaped, 1 to many cm. Cells 300-500 µm diameter. Growth diffuse. Well-developed rhizoidal system absent; basal cells in contact with the substratum provide attachment. Structural reinforcement of cell cushion by many uniform rows of minute determinate, simple or furcate, tenacular cells formed between appressed surfaces of all cells. Tenacular cells occasionally functioning as adventitious rhizoids. Cell division exclusively by segregative cell division, sensu stricto. Cells multinucleate; chloroplasts numerous per cell and discoid, with single pyrenoid surrounded by starch sheath and divided into two to multiple potions by traversing thylakoids. The life history biphasic with and isomorphic alternation of generations. Zoospores quadriflagellate and gametes isogamous and biflagellate. Thallus fragmentation and possible parthenogenetic development of gametes implicated, the latter resulting in thalli with smoother surface textures. Haploid and diploid chromosome numbers of 14 and 24 reported for D. intermedia and D. carvernosa, respectively. Nuclear DNA amounts of 1.79, 2.3 and 4.3 pg (1C, 2C, 4C) estimated for D. cavernosa. Dictyosphaeria widely distributed throughout the tropics in shallow intertidal habitats, often in coral rubble areas. On some reef flats it can become the dominant algae (e.g., parts of Kaneohe Bay, Oahu, Hawaii). D. cavernosa and D. versluysii best known species. D. cavernosa also abundant in metahaline near-shore pool in the Red Sea. Dictyosphaeria has always been allied with Valonia based on segregative division (sensu Egerod). Segregative division s.s., combined with immunological data and character compatibility analyses, indicate that Dictyosphaeria is most closely related to Siphonocladus, and more distantly to Ventricaria (formerly Valonia). Ribosomal RNA sequence data place Dictyosphaeria in the cladophoralean clade which supports earlier ultrastructural studies on the flagellar apparatus. Ultrastructural studies also carried out on cytokinesis, zoospore formation, chloroplasts and cell walls.

Information contributed by: J.L. Olsen. The most recent alteration to this page was made on 2022-06-29 by M.D. Guiry.

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

Gender: This genus name is currently treated as feminine.

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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. 29 June 2022. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 25 April 2024