Cenacrum R.W.Ricker & Kraft, 1979

Holotype species: Cenacrum subsutum R.W.Ricker & Kraft

Original publication and holotype designation: Ricker, R.W. & Kraft, G.T. (1979). Morphology of the subantarctic red alga Cenacrum subsutum gen. et sp. nov. (Rhodymeniales) from Macquarie Island. Journal of Phycology 15: 434-444.

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Description: Thallus with a discoid holdfast and erect, simple, forked or highly dissected, flattened fronds.Structure multiaxial, cortex of four or five layers of small cells, the outermost of which are anticlinally elongated.Medulla consisting of cavities lined with rhizoidal filaments bearing occasional, isolated secretory cells and filled with a weak mucilage when young, becoming filled with oblong, rounded cells and additional filaments when older. Gametangial plants dioecious; spermatangial sori superficial, scattered, spermatangia cut off terminally from elongated initials modified from cortical cells. Procarpic, carpogonial branches in cortex, (3-) 4-celled, formed on a large supporting cell with a 2-celled auxiliary cell branch, gonimoblast developing outwards from a fusion cell.Cystocarps ostiolate, scattered, never coronate, protruding outwards and inwards, most cells forming carposporangia in 2-3 lobes of different ages, tela arachnoidea absent. Tetrasporangia formed terminally from cortical filaments in nemathecia composed of cortical files 8-10 cells in length.Spores regularly cruciately arranged.

Information contributed by: M.D. Guiry. The most recent alteration to this page was made on 2010-10-08 by M.D. Guiry.

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

Most recent taxonomic treatment adopted: Saunders, G.W., Strachan, I.M. & Kraft, G.T. (1999). The families of the order Rhodymeniales (Rhodophyta): a molecular-systematic investigation with a description of Faucheaceae fam. nov. Phycologia 38: 23-40.

Comments: Nothing is known of the growth of Cenacrum subsutum in culture, although it is likely to have a ‘Polysiphonia-type’ life history. Large, blade-like, solid or partially ‘hollow’ species of the Rhodymeniaceae, such as species of Cenacrum, Hymenocladia, Hymenocladiopsis and Leptosomia (q.v.) are known only from the colder waters of the southern hemisphere; although closely similar in external appearance these genera are easily distinguished by anatomical and reproductive features.The combination of terminally-formed, tetrasporangia with cruciately arranged spores occurring in nemathecia on a thallus that forms mucilage-filled spaces in the younger parts of the frond is unique to this genus amongst the genera of the Rhodymeniales. < currently known only from Auckland, Macquarie, and Snares Is., is one of the largest red algae, reaching lengths of 85 cm (Ricker 1987). Plants occur in relatively sheltered waters at depths up to 20 m, although populations are commonest on rocky surfaces exposed to full light in shallow water (Ricker 1987).

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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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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 08 October 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 02 October 2023

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