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Order Rhodymeniales

Family Rhodymeniaceae

Rhodymenia natalensis Kylin 1938:13-14, pl. 5, fig. 13

Plants erect, 8 (-12) cm tall, bright red, with terete stipes and dichotomously branched flat blades. Small discoid holdfast bears longish (10-12 mm) terete stipe, often with horizontal stolons giving rise to further upright axes; blades flat, 1-2 (-3) mm wide, repeatedly dichotomously branched, about 200 µm thick, apices rounded to tapering. Structure pseudoparenchymatous; in cross-section stipe with medulla of round cells 30-50 µm in diameter, cortex of radiating rows of smaller (4-5 µm) cells; blade with medulla of about 5 layers of rounded hyaline (clear) cells up to 80 µm diameter and cortex of 2-3 layers of much smaller cells (about 5 µm diameter at surface). Tetrasporangia cruciately divided, about 20-25 x 10-20 µm in size, in sori in cortex near apices of blades.

Collections, ecology and regional distribution

Found along the southern African coast from Namibia (Wynne 1986) to northern KwaZulu-Natal (1-58 in South Africa) and into southern Mozambique (Isaac 1956). Epilithic subtidally and in the sublittoral fringe, where it often forms patches on steep or overhanging rocks.

World distribution: southern African endemic.

Type locality: Isipingo, Kwazulu-Natal (Silva et al. 1996).

Note: This species is variable in size and shape, from plants a few cm long and 1mm wide to others 12 cm long and 2-3 mm wide. The similar entity identified from Namibia as R. linearis J.Ag. by Wynne (1986) and from Cape Hangklip on the South African west coast (Jackelman et al. 1991) is considered by Stegenga et al. (1997) to be R. natalensis.


Rhodymenia natalensis, Kenton-on-Sea.

Rhodymenia natalensis, Mntafufu, Transkei (BOL).

Rhodymenia natalensis, cross section.

Rhodymenia natalensis. 1. Habit. 2. Section of ‘stipe’. 3. Section of tetrasporangial sorus. Reproduced from Stegenga et al. (1997).


References Rhodymenia natalensis

Isaac, W.E. 1956. Marine algae of Inhaca Island and of the Inhaca Peninsula. I. Journal of South African Botany 22: 161-193.

Jackelmann, J.J., Stegenga, H.S. & Bolton, J.J. 1991. The marine benthic flora of the Cape Hangklip area and its phytogeographical affinities. South African Journal of Botany 57: 295-304, 4 figs, 1 table.

Kylin, H. 1938. Verzeichnis einiger Rhodophyceen von Südafrika. Acta Universitatis Lundensis 34(8): 1-26, 10 figs, 8 plates.

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

Wynne, M.J. 1986. Report on a collection of benthic marine algae from the Namibian coast (southwestern Africa). Nova Hedwigia 43: 311-355, XXIV plates.


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,; Accessed on 26 February 2024.