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Order Gigartinales

Family Phyllophoraceae

Genus Gymnogongrus Martius

Gametophytes erect, leathery or cartilaginous, terete or flattened, more-or-less regularly dichotomously branched. Anatomy pseudo-parenchymatous, with medulla of relatively large cells interspersed with smaller cells and cortex of anticlinal rows of small cells. Sporophytes either separate, crustose thalli or borne on the gametophyte in the form of pustular nemathecia. Tetrasporangia in catenate series, cruciately divided.

Note: Silva and DeCew (1992) erected the genus Ahnfeltiopsis to include species previously assigned to Gymnogongrus and Ahnfeltia that have immersed cystocarps and a crustose tertrasporophyte in their life history. These they distinguished from species with “tetrasporopblastic” nemathecia borne on the gametophyte (which remained in Gymnogongrus). They published new combinations, including the South African species Ahnfeltiopsis complicata, A. vermicularis, A. glomerata, A. polyclada, and A. intermedia. (see also Stegenga et al. 1997). However, a molecular study by Fredericq et al. (2003) showed that some species show both types of life history, and some species with immersed cystocarps are more closely related to some with nemathecia than other “Ahnfeltiopsis” species. They therefore questioned the validity of Ahnfeltiopsis and noted the need for molecular studies of the genus worldwide. On these grounds we retain the original concept of the genus Gymnogongrus, which includes the South African species previously ascribed to Gymnogongrus as well as to Ahnfeltiopsis sensu Silva and DeCew (1992). Anderson & Bolton (1990) report on the life histories of South African species.

Key to species

1 a. Axes always terete

G. polycladus

b. Axes flattened or compressed

2

2 a. Axes flattened (strap-shaped); when fertile, cystocarps immersed

G. glomeratus

b. Axes compressed; when fertile, pustule-like external nemathecia present

G. tetrasporifer

 

References Gymnogongrus

Anderson, RJ, & JJ Bolton, 1990. Reproductive morphology and life histories of southern African Gymnogongrus species (Rhodophyta, Phyllophoraceae). British Phycological Journal 25: 381-390.

Fredericq, S., RJ Anderson & J. Lopez-Bautista. 2003. Systematic circumscription of some Phyllophoraceae from the Cape region, South Africa, based on morphological andmolecular evidence. Proc. 17th International Seaweed Symposium, Oxford University Press, pp. 263-273.

Silva, PC, & DeCew, T.C. 1992. Ahnfeltiopsis, a new genus in the Phyllophoraceae (Gigartinales, Rhodophyta). Phycologia 31: 576-580.

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 15 November 2018.