Reproductive phenology, zygote embryology and germling development of the threatened Carpodesmia barbatula (= Cystoseira barbatula) (Fucales, Phaeophyta) towards its possible restoration

Carpodesmia barbatula (= Cystoseira barbatula) (Fucales, Phaeophyta) is a species endemic to the Southern Mediterranean Sea, which grows in clean waters on exposed sublittoral rocky shores. Together with other species of the genus Cystoseira sensu lato, it is an ecosystem engineer that forms dense canopy forests, sustaining biodiversity, productivity and nutrient cycling in temperate rocky reefs. Human impacts and climate stressors are seriously hampering these ecosystems and actual conservation efforts appear insufficient for their preservation. Restoration actions could be a solution for the loss of these habitats, but they require the deep knowledge of the target species. In the present study, we describe egg release, zygote development and germling growth of C. barbatula, poorly known, despite its importance in the upper sublittoral seaweed flora. The aim is to improve the knowledge on the early life stages of this rare and threatened species, towards its possible future restoration.