Two new species of Centroceras (Ceramiaceae, Rhodophyta) from KwaZulu-Natal, South Africa

Abstract

Two distinct species of Centroceras from South Africa that were previously referred to as Centroceras sp. 2 and Centroceras sp. 3 on the basis of comparative rbcL sequence analysis are here newly described on the basis of vegetative morphology. Centroceras hommersandii sp. nov. is characterized at the nodes by an elongated cortical cell derived from the second cortical initials, a flattened gland cell and a cortical cell cut off from the first cortical initials, straight spines, 13–14 periaxial cells, and by tetrasporangia not associated with involucral branchlets. Centroceras natalensis sp. nov. is characterized at the nodes by an ovoid cortical cell on the second cortical initial, a flattened gland cell and a cortical cell produced from the first cortical initial, straight spines, and 12–14 periaxial cells. Other species of Centroceras examined possess either only a flattened gland cell cut off from the first cortical initials (in C. clavulatum, C. rodmanii, C. tetrachotomum), or an ovoid gland cell with a cortical cell (in C. gasparrinii, C. hyalacanthum, C. internitens, C. micracanthum). Centroceras hommersandii sp. nov. is also distinguished by an elongated acropetal cortical cell formed only on the second cortical initial, whereas other species (C. hyalacanthum, C. internitens, C. micracanthum) have elongated acropetal cells present on both the first and second cortical initials. A key to the South African species of Centroceras is provided.