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Order Ceramiales

Family Ceramiaceae

Centroceras Kützing

Thallus with conspicuous large-celled central filament, each cell cutting off a ring of periaxial cells at the apical face, subsequently developing a complete cortication. Cortex consisting of remarkably straight rows of rectangular cells, developing almost exclusively in basipetal direction. In most species spines and/or gland cells developing along the apical margins of the cortical bands. Tetrasporangia borne on periaxial or (less usually) on other cortical cells, immersed or exserted, tetrahedrally divided. Spermatangia cut off from cortical cells over large parts of the thallus. Carposporophytes with an involucre of cortical filaments. (Description based on Stegenga et al. 1997).

Distinctions between species are largely based on the morphology of cortical filaments, including shape and number of acropetal cortical cells and the shape of gland cells and spines (See Won et al. 2009, 2010). Seventeen species are currently recognized (Guiry & Guiry 2015), among which five are recorded from South Africa, but the number on the south coast is unknown (see note below).

Note: Previously, Centroceras clavulatum (C. Agardh) Montagne was considered to occur throughout South Africa (Stegenga et al. 1997). This species, the type of which comes from Peru, was “often cited as being a prime example of a cosmopolitan red algal species” (Won et al. 2009). However, these authors used morphological and molecular methods to show that C. clavulatum comprises nine species, among which they recorded four (but not C. clavulatum) in South Africa. Two of the South African species were described from the west coast by Won et al. (2009): Centroceras tetrachotomum sp. nov. and C. gasparrinii (Meneghini) Kützing. Two more were described from KwaZulu-Natal by Won et al. (2010): C. hommersandii sp. nov. and C. natalensis sp. nov. A fifth species, C. distichum Okamura, was previously recorded from one subtidal locality in the Western Cape (Jackelman et al. 1991).

Both Won et al. (2009) and Won et al. (2010) based their descriptions of South African records on specimens from very few localities (usually one). Furthermore, almost all existing South African specimens were previously identified as C. clavulatum. The result is that without a detailed re-examination of existing collections (and new collections), we do not know the distribution ranges of these species, or which of them might occur on the south coast (only one south coast locality is cited for one species: C. gasparrinii, from Mzamba). Until Centroceras on the South Coast can be examined further, we provide only a description and illustrations of typical C. “clavulatum” as we previously recognized it from this region. For proper identification of South African Centroceras species, refer to Won et al. (2009) and Won et al. (2010), and particularly to the key to South African species in the latter publication.

References Centroceras

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 24 November 2015.

Jackelman, J.J., Stegenga, H. & J J Bolton. 1991. The marine benthic flora of the cape Hangklip area and its phytogeographical affinities. South African Journal of Botany 57: 295-304.

Stegenga, H., Bolton, J.J. & R. J. Anderson. 1997. Seaweeds of the South African west coast. Contributions from the Bolus Herbarium 18: 655 pp.

Won, B.Y., Cho, T.O. & Fredericq, S. 2009. Morphological and molecular characterization of species of the genus Centroceras (Ceramiaceae, Ceramiales), including two new species. Journal of Phycology 45: 227-250.

Won, B.Y., Fredericq, S. & Cho, T.O. 2010. Two new species of Centroceras (Ceramiaceae, Rhodophyta) from KwaZulu-Natal, South Africa. European Journal of Phycology 45(3): 240-246.

 

Cite this record as:

Anderson RJ, Stegenga H, Bolton JJ. 2016. Seaweeds of the South African South Coast.
World Wide Web electronic publication, University of Cape Town, http://southafrseaweeds.uct.ac.za; Accessed on 20 November 2018.