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Order Ceramiales

Family Rhodomelaceae

Laurencia alfredensis Francis, Bolton, Mattio et R.J. Anderson in Francis et al. 2017: 810-811, Fig. 3

Plants dark red to purplish-red, epilithic, up to 35 cm tall; axes compressed, 1-3 mm wide and 0.5-1 mm thick. Holdfast stoloniferous, thalli complanate, main axes percurrent, branching alternate in up to 4 orders. Branches basally constricted; ultimate branchlets wider than long, with truncated apices. In cross-section axial (central) and periaxial cells clearly visible. Periaxial cells to more than 100 um wide; cells becoming smaller outwards; outer cortical cells up to 60 um wide. Outermost cortical cells each containing 4-6 small corps en cerise. Cystocarps up to 500 um in diameter, on penultimate branchlets. Tetrasporophytes and male gametophytes not seen.

Collections, ecology and regional distribution

So far recorded from Grootbank (Tsitikamma area) to Double Mouth (31-43) but probably more widespread because previous collections would have been identified as L. flexuosa (see note). Found in lower eulittoral and shallow sublittoral zones.

Word distribution: apparently a South African endemic.

Type locality: Port Alfred, Eastern Cape Province, South Africa (Francis et al. 2017).

Note: L. alfredensis is morphologically very similar to L. flexuosa, and only DNA analysis led to them being recognised as separate species, after which some morphological differences were found (Francis et al. 2017). Under a compound microscope the easiest way to distinguish fresh material of the two species is by the number of corps en cerise per outer cortical cell: 4-6 in L. alfredensis vs 1-3 in L. flexuosa.

 


Laurencia alfredensis, Double Mouth.


Laurencia alfredensis, frond detail.


Laurencia alfredensis, alternate branching, with cystocarps near apices.


Laurencia alfredensis, surface view showing 4-6 small corps en cerise in each outer cortical cell.

 

References Laurencia alfredensis

Francis, C.M., Bolton, J.J., Mattio, L., Mandiwana-Neudani, T. & Anderson, R.J. 2017. Molecular systematics reveals increased diversity within the South African Laurencia complex (Rhodomelaceae, Rhodophyta). Journal of Phycology 53: 804-819.

 

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 20 September 2018.