Where have all the youngest gone? The post-larval and young stages of the Mediterranean endangered limpet Patella ferruginea Gmelin, 1791

Recruits of Patella ferruginea are hardly seen in their habitat; hence, the precise level where they settle and the morphology of the earliest growth stages remain unknown. The earliest post-larval stages of this species are described here for the first time, based on specimens obtained both through controlled reproduction and in its natural environment in Chafarinas Islands (North Africa). Young post-larval specimens of 290 μm in length settled slightly below the water level on floating Petri dishes in the aquaculture tank. Specimens of approximately 4 mm were found in the natural habitat at the level of the vermetid gastropod Dendropoma lebeche, whereas those larger than 8 mm were also found at this level, but also in the upper midlittoral, at the Chthamalus spp. fringe. The characteristic star-like shell and colour pattern of young specimens, with alternating concentric dark and light bands, appeared at approximately 8 mm in length. Smaller specimens have a more or less oval shell and dark radial bands. This information is useful for future non-invasive studies on the recruitment of this endangered species, but further information about the post-larval stages of the other three Mediterranean patellid species is needed to distinguish specimens smaller than 3 mm.This work was funded by the project “Action plan for viability proposals of the endangered limpet, Patella ferruginea” (Project 0 of the Spanish Research Council–CSIC- Foundation) and former grants awarded by the Organismo Autónomo Parques Nacionales and the Dirección General de Conservación de la Naturaleza of the Spanish Ministerio de Agricultura, Alimentación y Medio Ambiente (MAGRAMA)Peer reviewe