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Order Gigartinales

Family Gigartinaceae

Gigartina Stackhouse 1809: 55

Thalli usually erect, ranging in shape from foliose to narrowly pinnate. Plants may be large and foliose or small and procumbent, with creeping hapterous holdfasts. Thalli often bear superficial branchlets or papillae. Growth is by meristems located in apices or thallus margins. Cystocarps are conspicuous and found in papillae or swellings on the surfaces and/or margins of thalli. A filamentous sheath surrounds the carposporophyte and carpospores are released through ostioles. Tetrasporangia are formed in sori at the inner cortex/medulla boundary, from inner cortical cells. Tetraspores are released in a gelatinous matrix by excision of soral tissue.

According to Guiry & Guiry (2012), 38 species are currently recognized in the genus Gigartina, which is distributed throughout cool to cold temperate seas. South Africa (along with Chile, Japan, New Zealand and California) is recognized as a centre of rich species diversity.

Key to species

1a. Axes terete or almost terete

2

1b. Axes compressed or flattened (blades)

4

2a. Thallus irregularly branched, small (diameter ca.1 mm, up to 1.5 cm high)

G. minima

2b. Thallus dichotomously branched, large (diameter 2-3 mm, up to 20 cm high)

G. pistillata

3a. Blades with smooth surfaces but small branchlets along margins

G. insignis

3b. Blade surfaces rough in mature thalli, with papillae or peg-like outgrowths

4

4a. Blades ovate, covered in papillae

G. polycarpa

4b. Blades wedge- or strap-shaped, with peg-like superficial outgrowths

G. paxillata

 

References Gigartina

Guiry, M.D. & Guiry, G.M. 2012. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched October 2012.

Stackhouse, J. 1809. Tentamen Marino-Cryptogamicum. Mémoires de la Société Impériale des Naturalistes de Moscou, 2: 50-97.

 

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 September 2018.