Semnocarpa Huisman, H.J.Foard & Kraft, 1993

Holotype species: Semnocarpa corynephora (J.Agardh) Huisman, Foard & Kraft

Original publication and holotype designation: Huisman, J.M., Foard, H.J. & Kraft, G.T. (1993). Semnocarpa gen. nov. (Rhodophyta: Rhodymeniales) from southern and western Australia. European Journal of Phycology 28: 145-155, 30 figs.

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Precise date of publication: Aug 1993

Description: Thallus erect, filled with a watery mucilage throughout, terete or slightly compressed, main axis percurrent, branching alternate, radial or subopposite; holdfast discoid or crustose; multiaxial construction, cortex tubular, composed of 2-3 cell layers lined inside with a network of regularly arranged medullary filaments bearing internally-directed secretory cells and compacted into a plug at branch bases, monostromatic septa absent. Gametangial plants dioecious; spermatangia in superficial sori, terminal on mother cells derived from cortical cells; procarpic, carpogonial branches 3-celled, with a single 2-celled auxiliary cell branch, gonimoblast developing outwards from a compact fusion cell, most cells forming carposporangia, tela arachnoidea laxly developed, cystocarps scattered, wholly internal, with a pore; tetrasporangia terminal on cortical filaments, in sori in depressions formed by invagination of cortex, tetrahedral, polysporangia unknown.

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: 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: Semnocarpa is placed in the Lomentariaceae because of its anatomical and reproductive similarity to species of Lomentaria and Binghamiopsis: its carpogonial branch is 3-celled; single-layered cellular diaphragms are absent; virtually all gonimoblast cells function as carposporangia; tetrasporangia are formed from terminal rather than intercalary cells. The sunken cystocarp is unique in the Rhodymeniales; although sunken or partially sunken cystocarps occur in species of Botryocladia, Cenacrum, Chrysymenia, Gloiosaccion, and Webervanbossea, in all of these entities there is an invagination of the hyaline inner cortical layer and this layer persists in the mature cystocarp. In Semnocarpa, on the other hand, all that surrounds the cystocarp is a loose jacket of filaments. In the other two families of the order, the Lomentariaceae and Champiaceae (Lee 1978), the cystocarps of previously described genera are strongly protuberant. However, despite its sunken cystocarps, Semnocarpa clearly belongs to the Lomentariaceae as other features of its structure and reproduction (notably the formation of terminal tetrasporangia in invaginated sori) clearly align it with this family (Huisman, Foard & Kraft 1993). Nothing is known of the life history or sequence of genetic or morphological phases; it is likely, however, that the life history is of the Polysiphonia-type. Semnocarpa is known only from two Australian species. S. corynephora is a rare component of the spring to early summer drift in Victoria, South and Western Australia, mainly as an epiphyte; the only in situ collection is from rocks at 30-32 m. S. minuta is known only from Western Australia where it grows epiphytically on a range of seaweeds and seagrasses at depths of 2-6 m. S. minuta is 1-30 mm in length with several erect axes arising from a common crustose base; S. corynephora attains lengths of 20 cm and arises singly from a discoid base.

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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. 08 October 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 29 March 2024

 
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