Valid XHTML 1.0 Transitional

Order Gracilariales

Family Gracilariaceae

Gracilaria Greville

Plants branched, varying in form from terete to flattened, and in size from a few cm to over 60 cm in length. Holdfast discoid or crustose, bearing one to many erect axes. Plants soft, cartilaginous, or leathery; smooth, dentate, or fimbriate; varying in colour from red, red-brown, olive, green, purple, to yellowish. Anatomy of pseudoparenchymatous medulla and cortex of one to several layers of smaller cells. Life history triphasic, isomorphic. Cystocarps visible as swellings; ostiolate, traversed by tubular nutritive cells that connect the gonimoblast to the pericarp; carposporangia catenate. Tetrasporangia either scattered or in nemathecia.

The genus is well-represented in tropical and temperate waters worldwide, with 167 species currently recognised (Guiry & Guiry, 2011). Five species are recorded from the South African south coast. South African Gracilaria and Gracilariopsis species are described in detail by Iyer et al. (2004), and the molecular systematic of the Gracilariacaeae discussed by Iyer et al. (2005a). Gracilaria is one of the most important genera of commercial seaweeds in the world, and many species are harvested or cultivated for their agar.

 

Key to species

1a. Plants terete, soft, stringy, about 1 mm in diameter, up to 60 cm long

G. gracilis
(see also Gracilariopsis)

1b. Plants terete or flattened, more than 1 mm wide, not stringy

2

2a. Plants terete, cartilaginous; whorls of teeth on axes

G. aculeata

2b. Plants with flat blades

3

3a. Blades wide (to 3 cm or more), plants large (to 25 cm)

G. capensis

3b. Blades less than 2 cm wide

4

4a. Blades less than 1 cm wide, blade surfaces smooth

G. beckeri

4b. Blades up to 16 mm wide, sparsely branched, surfaces of mature blades dentate or papillate

G. denticulata

 

References Gracilaria

Guiry, M.D. & Guiry, G.M. 2011. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched October 2011.

Iyer, R., De Clerck, O, Bolton J.J. and V.E. Coyne. 2004. Morphological and taxonomic studies of Gracilaria and Gracilariopsis species (Gracilariales, Rhodophyta) from South Africa. South African Journal of Botany 70: 521-539.

Iyer, R., Tronchin, E. M. and J. J. Bolton. 2005a. Molecular systematics of the Gracilariaceae (Gracilariales, Rhodophyta) with emphasis on southern Africa. Journal of Phycology 41: 672-684.

 

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 25 September 2018.