The genus Gracilaria (Rhodophyta, Gigartinales) in the western Atlantic. <i>Gracilaria domingensis, G. cervicornis</i>, and <i>G. ferox</i>

Abstract

Three frequently confused species of Gracilaria Greville, G. domingensis Sond. Ex Kütz., pro syn., G. cervicornis (Turn.) J. Ag., and G. ferox J. Ag. have been reassessed. Gracilaria domingensis, despite morphological similarity to the other two species, is clearly distinct by virtue of having spermatangia in deep crypts and a thin cortex of subquadrate cells. Not only do G. cervicornis and G. ferox share the characteristics of spermatangia in shallow conceptacles and a multilayered cortex of radially elongated cells but they are anatomically indistinguishable and have identical distributions in the western Atlantic. This plus the range of morphologies intermediate between the typical forms support a reduction of this complex to a single species, G. cervicornis. The presence of small interstitial cells in the medulla of these plants is documented, and detailed descriptions of the species are provided.