Echinoderms, especially sea urchin is a keystone species in the ecosystem such as coral reefs. We have chosen to investigate well-studied species complexes of sea urchin (phylum Echinodermata ; Class Echinoidea), which are widespread and abundant in the Indo-Pacific ecosystems and are known to be sentinel species of marine ecosystems. The study will focus on two genera : Diadema spp. and Echinometra spp. The main goal of the study is to understand the biodiversity and the phylogeography of those genera.