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Order Dictyotales

Family Dictyotaceae

Dictyota naevosa (Suhr) Montagne 1840: 145

Thalli erect, up to about 35 cm tall, pale brown to yellowish-brown with blue iridescence. Thallus by a matted rhizoidal holdfast. Branches to about 1 cm wide, branching sub-dichotomous, in up to 10 orders; final branches up to 10 cm long, apices rounded. Internal structure usually of single layer of medullary cells covered on each surface by single layer of cortical cells, but sometimes all layers are duplicated. Cortical cells ca. 25 µm deep and 10-15 µm wide; medullary cells ca. 115 µm long, 70 µm wide and 130-160 µm high. Tetrasporangial sori on both frond surfaces, elongate-ovoid, up to about 1.5 mm long, often with central hair tufts; tetrasporangia to about 80 µm in diameter. Oogonial sori elongate-ovoid sori, on average about 400x300 µm , distributed evenly over blade surface, without hair tufts; oogonia clavate, about 90x40 µm . Antheridial sori uniformly distributed over blade surface and often merging into patches, associated with hair tufts; surrounded by 3-6 rows of unicellular clear paraphyses. Further details in Tronchin & De Clerck (2005) and Stegenga et al. (1997).

Collections, ecology and regional distribution

Recorded from False Bay around the whole south coast and as far east as Mission Rocks in northern KwaZulu-Natal (17 -57). Common, epiphytic and epilithic in rock pools, the sublittoral fringe and shallow sublittoral on wave-exposed coasts; often in sand-affected gulleys.

World distribution: also recorded from the Canary Islands, Senegal, Japan and South and Western Australia (references in Guiry & Guiry 2016).

Type locality: Algoa Bay, South Africa (Silva et al. 1996).


Dictyota naevosa, De Hoop. Note bluish iridescence.

Dictyota naevosa, section though part of an oogonial sorus showing oogonia, cortex and part of medullary cells.

Dictyota naevosa, surface view of thallus showing oogonial sori (dark patches).

Dictyota naevosa, s. 1 Habit. 2 Thallus apex. 3 Oogonia in cross section of thallus. Reproduced from Stegenga et al. (1997).


References Dictyota naevosa

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2016. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 08 March 2016.

Montagne, C. (1840). Plantae cellulares. In: Histoire naturelle des Iles Canaries. (Barker-Webb, P. & Berthelot, S. Eds) Vol.3, part 2, sect. ultima [4], pp. 137-192. Paris: Mellier.

Silva, P.C., Basson, P.W. & Moe, R.L. (1996). Catalogue of the benthic marine algae of the Indian Ocean. University of California Publications in Botany 79: 1-1259.

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

Tronchin, E.M. & De Clerck, O. (2005). Brown algae. Phaeophyceae. Guide to the seaweeds of KwaZulu-Natal. Scripta Botanica Belgica 33: 95-129.


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 24 September 2018.