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Order Caulerpales

Thallus coenocytic but crossed by trabeculae, differentiated into a horizontal stolon attached by short rhizoidal outgrowths and upright assimilators (fronds). Numerous chloroplasts in lumen, parietal together with storage bodies (amyloplasts). Life-history diplontic.

Family Caulerpaceae Greville ex Kützing

Contains the single genus Caulerpa.

Genus Caulerpa Lamouroux

Thallus coenocytic, differentiated into horizontal stolons, colourless rhizoidal haptera, and upright photosynthetic assimilators (fronds) of various shapes. Thallus internally undifferentiated except for trabeculae - extensions of the cell wall that run across the lumen.

Caulerpa is a large genus, with about 84 species currently recognized (Guiry & Guiry 2014), mainly tropical in distribution. Some species produce a poison, caulerpicin, which deters certain grazers and may make them toxic to humans. The thalli heal wounds (e.g. caused by fish grazing) by secreting a polysaccharide plug into the opening.

The morphological variability of many Caulerpa species has led to the description of numerous forms and varieties. Molecular studies have reduced the numbers of sub-specific taxa: in this guide we have not distinguished sub-specific taxa. We recognize six species from the south coast, with more species appearing in the tropical waters of northern Kwazulu-Natal (Coppejans et al. 2005).

Key to the species

1a. Erect fronds (assimilators) pinnate and neatly feather-like

C. holmesiana

1b. Assimilators not feather-like


2a. Branching dichotomous, assimilators strap-shaped


2b. Branching radial or distichous, assimilators globose or pear-shaped


3a. Assimilators long (10-30 cm) and wide (3-6 mm)

C. filiformis

3b. Assimilators short (1-5 cm) and 1.5 - 3 mm wide


4a. Assimilators several times dichotomously branched

C. bartoniae

4b. Assimilators not several times dichotomously branched

C. brachypus

5a. Assimilators spherical, on radially-arranged branchlets

C. racemosa

5b. Assimilators pear-shaped, branchlets alternate or opposite

C. zeyheri



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.