South African Seaweeds

Order Ceramiales

Family Ceramiaceae

Ceramium Roth

Plants erect or prostrate, thalli with conspicuous central filaments of globose, ellipsoid, biconical or cylindrical cells, each cutting off a ring of periaxial cells at the apical face; degree of subsequent development of cortication very variable within the genus. Number of periaxial cells 4-10. Main branching pattern varying from regularly pinnate to dichotomous, adventitious branchlets often present. Thallus apices incurved or straight. Tetrasporangia inserted on periaxial cells, less frequently also on other cortical cells. Sporangia immersed or exserted, tetrahedrally divided. Spermatangia cut off from cortical cells over large parts of the thallus. Female fertile filaments producing carpogonial filaments on several segments; carposporophytes with an involucre of corticated filaments. (Description from Stegenga et al. 1997).

Ceramium is a common genus (207 species are flagged as currently accepted taxonomically by Guiry & Guiry 2015), found in almost all marine floras. We record at least 14 species on the South African south coast, excluding those that should be assigned to Gayliella (see later). The main characters used to separate species are the pattern of nodal cortication, habit and branching pattern, incurvature of thallus apices, and tetrasporangial characters.

Note: The genus Gayliella was erected on molecular and morphological grounds (Cho et al. 2008) to include mostly former Ceramium species of the C. flaccidum complex. The main difference between the genera is that in Gayliella the cortical bands show a clear division between acropetal and basipetal cortication, with the pericentral cells giving off two acropetal and one basipetal derivatives, whereas in Ceramium the cortical bands lack a clear division between acropetal and basipetal cortication, and the pericentral cells usually give off two acropetal and two (or three) basipetal derivatives, although sometimes basipetal cortication is absent. Three former south coast Ceramium species are affected (see key below): only one, G. tranversalis, was formally transferred by Cho et al. (2008). We have placed the other two in Gayliella. The key contains both the genera Ceramium and Gayliella, but the descriptions of these three species are under Gayliella, for which we also provide a separate key.

Ceramium and Gayliella– key to the species

1a. Cortical bands with a clear division between acropetal and basipetal cortication, the pericentral cells giving off two acropetal and one basipetal derivatives (genus Gayliella)	2
1b. Cortical bands without a clear division between acropetal and basipetal cortication, the pericentral cells usually giving off two acropetal and two (or three) basipetal derivatives, sometimes however basipetal cortication absent	4
2a. Axes to about 50 μm in diameter, with four periaxial cells	*Gayliella tranversalis*
2b. Axes to 100 μm or more in diameter, with five or more periaxials	3
3a. Axes to 120 μm in diameter, segments with 5 or 6 periaxials	*Gayliella dawsonii ex Ceramium dawsonii*
3b. Axes to over 200 μm in diameter, segments with 7 (or 8) periaxials	**Gayliella papenfussiana ex Ceramium papenfussianum**
4a. Species with very conspicuous multicellular spines	Ceramium juliae
4b. Species without spines	5
5a. Cortication continuous	6
5b. Cortication discontinuous	10
6a. Main axes prostrate, mainly growing on corallines	*Ceramium poeppigianum*
6b. Main axes erect	7
7a. Cortication in fairly regular vertical rows	*Ceramium centroceratiforme*
7b. Cortication not in regular vertical rows	8
8a. Tetrasporangia completely exserted	*Ceramium planum*
8b. Tetrasporangia immersed	9
9a. Tetrasporangia often in short stichidium-like branchlets	*Ceramium obsoletum*
9b. Tetrasporangia in the apical parts of the thallus	*Ceramium graecum/lenticulare*
10a. Cortication in fairly regular vertical rows	*Ceramium centroceratiforme*
10b. Cortication not in regular vertical rows	11
11a. Each segment with a ring of very prominent gland cells	*Ceramium glanduliferum*
11b. Gland cells, when present, not much larger than other cortical cells	12
12a. Branching of the main axes every second segment	*Ceramium callipterum*
12b. Branching of the main axes at longer intervals	13
13a. Branching at intervals of 3 (occasionally 4) segments	14
13b. Branching at longer intervals	16
14a. Thallus mainly creeping, with massive rhizoid bundles	*C. sp. 2*
14b. Thallus (mainly) upright	15
15a. Cortication limited to 1 or 2 rows of cells, tetrasporangia completely exserted	*Ceramium aff. callipterum*
15b. Cortical bands broader, tetrasporangia immersed	*C. sp. 3*
16a. Apices of actively growing plants strongly incurved	17
16b. Apices of actively growing plants only moderately incurved or not at all	18
17a. Cortication developing in acropetal and basipetal direction to about the same extent	*Ceramium arenarium*
17b. Cortication developing almost exclusively in acropetal direction	*Ceramium tenerrimum*
18a. Apices straight, branching at intervals of 4-6(-7) segments	*Ceramium graecum/lenticulare*
18b. Apices moderately of slightly incurved. Branching at intervals of usually more than 6 segments	19
19a. Plants lax, winding between various seaweeds and inanimate substrata; tetrasporangia immersed.	*Ceramium camoui*
19b. Plants bushy, with a short (3-5 mm) apical part free from the substratum; tetrasporangia completely exserted	*C. sp.1*

Note: In addition to the species described here, below is a list of limited or uncertain records of species that we have not yet included, but which need further examination.

Ceramium codii (H. Richards) Feldmann-Mazoyer, Bird Island, 19-26 Aug. 1987.
Ceramium comptum Børgesen, Bird Island, 19-26 Aug. 1987.
Ceramium miniatum C. Agardh is recorded by Seagrief (1988) but we have not recognized it in the area.
Ceramium callipterum Mazoyer , Bird Island, 19-26 Aug. 198. Material probably identical to C. callipterum, not C. aff. callipterum in Stegenga et al. (1997) This specimen is branched every second segment (see Anderson & Stegenga 1989).
Ceramium fastigiatum (Roth) Harvey f. flaccidum H.E. Petersen, one specimen from Port Elizabth, one from Three Sisters.

References Ceramium

Anderson, R.J. & H. Stegenga 1989. Subtidal algal communities at Bird Island, Eastern Cape, South Africa. Botanica Marina 32: 299-311.

Cho, T.O., Boo, S.M., Hommersand, M.H., Maggs, C.A., McIvor, L.J. & Fredericq, S. 2008. Gayliella gen. nov. in the tribe Ceramieae (Ceramiaceae, Rhodophyta) based on molecular and morphological evidence. Journal of Phycology 44: 721-738, 11 figs.

M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2015. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 18 November 2015.

Seagrief, SC 1988. Marine Algae. In Lubke, RA, Gess GW & MN Bruton (Eds). Field Guide to the Eastern Cape Coast. Grahamstown Centre of the Wildlife Society of Southern Africa, 520 pp.

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

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, http://southafrseaweeds.uct.ac.za; Accessed on 24 April 2024.