Tetraspore germination of two vulnerable marine algae, Gelidium canariense and G. arbusculum (Rhodophyta, Gelidiales)

Gelidium canariense and Gelidium arbusculum coexist in the upper sublittoral zone in the Canary Islands and are the only Gelidiales registered as vulnerable species. Spore germination and the formation of rhizoids are vital steps for the successful growth of new plants. We investigated the initial germination stages of tetraspores and the growth of the primary rhizoid in these two vulnerable species. Both Gelidiales exhibited Gelidium-type germination. However, liberated tetraspores of G. canariense and G. arbusculum germinated earlier than those of other species of the Gelidiales. The growth curves of primary rhizoids were similar in both species.