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Order Dictyotales

Family Dictyotaceae

Zonaria subarticulata (J.V.Lamouroux) Papenfuss 1944: 339

Plants brown to greyish-brown, erect, up to 30 cm tall, flattened, profusely branched, comprising narrow (2-4 mm) strap-shaped blades arising from a matted rhizoidal holdfast. Branching in 2-3 orders, irregular, in single plane, branches at apex 3-4 mm wide, apices lobed. Blades 200-300 µm and 10-14 cells thick. Medulla of 8-12 cell layers, cells 15-20 µm in diameter, in longitudinal section ca. 80 µm long, cells containing many dark storage bodies imparting distinct banding pattern in longitudinal section. Cortex of smaller (20 µm diameter) pigmented cells; in cross section usually two cortical cells per medullary cell.

Unilocular sporangia in large sori, on both sides of the blade or more frequent on one side. Sporangia ovate, developing from an epidermal cell, at maturity ca. 150 X 75 μm, the contents developing into 8 spores. Majority of epidermal cells in a sorus each developing a multicellular paraphysis ca 7 cells long, narrow cylindrical at the base, the apical and subapical cells roundish and ca. 30 μm wide.

Plants dioecious. Female sori of much the same shape as sporangial ones but oogonia more slender than sporangia, ca. 185 X 60 μm; paraphyses in female sori of the same shape and density as in sporangial ones. Male gametangia in large sori covering much of the width of a blade. Male gametangia cylindrical, ca. 80 X 10 μm, about 30-35 cells high and 2-4 cells broad, with a sterile cell on top. Male sori without sterile filaments.

Collections ecology and regional distribution

Recorded from False Bay (but rare there) to northern Kwazulu-Natal (18-58). Common on the south coast in rock pools and the sublittoral zone down to 40 m depth. Often abundant on the walls of wave-washed gulleys.

World distribution: also recorded from Mozambique, Madagascar and the Mascarene Islands (Tronchin & De Clerck 2005).

Type locality: Madagascar (Silva et al. 1996).


Zonaria subarticulata, Arniston.

Zonaria subarticulata, longitudinal section through mid-blade.

Zonaria subarticulata, cross section through male sorus (Mkambati, stained slide preparation).

Zonaria subarticulata, cross section through probable female sorus (Mkambati, stained slide preparation).

Zonaria subarticulata, cross section through sorus of probable unilocular sporangia (Tsitsikamma, stained slide preparation).

Zonaria subarticulata, cross section through male sorus, detail (Mkambati, stained slide preparation).

Zonaria subarticulata, . 1. Habit. 2. Longitudinal section. 3. Cross section. Drawings reproduced from Stegenga et al. (1997).


References Zonaria subarticulata

Papenfuss, G.F. (1944). Notes on algal nomenclature. III. Miscellaneous species of Chlorophyceae, Phaeophyceae and Rhodophyceae. Farlowia 1: 337-346.

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. In: De Clerck, O., J.J.Bolton, R. J. Anderson and E. Coppejans, 2005. Guide to the Seaweeds of Kwazulu-Natal. National Botanic Garden of Belgium, Brussels (Scripta Botanica Belgica), pp. 96-129.


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 19 April 2024.