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Order Ceramiales

Family Rhodomelaceae

Bostrychia Montagne

Plants filamentous; main axes polysiphonous, with or without secondary cortication, pericentral cells divided transversely ; branching alternate, often regular, ultimate branches mono-or polysiphonous; vegetative trichoblasts absent. Tetrasporangia in stichidia in position of ultimate branchlets. Spermatangial heads cone-shaped, also as ultimate branchlets. Cystocarps borne on ultimate branchlets, globose to ovate. Sexual structures rare in most species.

The genus Bostrychia contains about 17 species worldwide (Guiry & Guiry, 2010), mainly from tropical and warm-temperate seas. Species are generally found at the edges of the marine environment, for example in estuaries and mangroves and in the upper eulittoral zone or supralittoral splash zone, for example in shaded overhangs, where they often form dark, fluffy turfs.

Seven species have been recorded from the South African south coast, but we have not collected all of them, and for some there is little or questionable material available for examination. Lambert et al (1987) provide detailed information on the distribution and morphology of most South African estuarine species.

Key to the species

1 a. Branching regular, alternate, pinnate, thallus neatly feather-like

B. tenella

1 b. Branching sparse to profuse, irregular or regular, thallus not feather-like


2 a. Main axis up to 600 µm in diameter

B. harveyi

2 b. Main axes less than 400 µm in diameter


3 a. Thallus with (usually) 8 pericentral cells, 4-5 tier cells per axial cell; habitat rocky shores

B. intricata

3 b. Thallus with <8 pericentral cells, either 2 or 3 tier cells per axial cell; habitat estuaries, salt marshes or mangroves


4 a. Pericentral cells divided into 3 tier cells per axial cell

B. tangatensis

4 b. Pericentral cells divided into 2 tier cells per axial cell


5 a. Main axes ca. 350 µm in diameter

B. radicans

5 b. Main axes ca. 120 µm in diameter


6 a. Thalli upright or repent, branches alternate, at intervals of 3-5 segments

B. moritziana

6 b. Thalli of branched prostrate axes bearing upright laterals at irregular intervals, laterals simple or branched in 1-2 orders

B. simpliciuscula


References Bostrychia

Guiry, M.D. & Guiry, G.M. 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched October 2010.

Lambert, G., T.D. Steinke & Y. Naidoo. 1987. Algae associated with mangroves in southern African estuaries. I. Rhodophyceae. South African Journal of Botany 53(5): 349-361.


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 02 March 2024.