Echinoid and asteroid species richness in different NW Pacific deep-sea areas. SoJ – Sea of Japan, SoO – Sea of Okhotsk, BS – Bering Sea, OA – open-oceanic abyssal, JT – Japan Trench, KKT – Kuril-Kamchatka Trench, AT – Aleutian Trench. SoJ, SoO, BS are outlined by 2000 m isobath; OA is outlined by 2,000 m isobath, 40°N latitude in the south and 180°E longitude in the east. JT, KKT and AT are outlined by 6,000 m isobaths. Species number for each region is given in circle: left half – Echinoidea, right half - Asteroidea.