Constantinos Petrinos / Yellow stripe clingfish (Diademichthys lineatus) living in association with the Fire Urchin (Astropyga radiata) Lembeh Strait, North Sulawesi, Indonesia.

Juergen Freund / Coleman shrimp (Periclimenes colemani) on a Fire urchin (Asthenosoma varium) Moluccas Islands, Indonesia.

Floris van Breugel / Giant Red Sea Urchins (Strongylocentrotus franciscanus) Purple sea urchins (Strongylocentrotus purpuratus) and Sea Anenomes (Anthopleura) underwater, in tide pools along Californian coastline, USA.

Fred Bavendam / Purple Sea Urchin (Strongylocentrotus purpuratus) and Red Sea Urchin (Strongylocentrotus franciscanus) group, Channel Islands, California

Flip Nicklin / Purple Sea Urchin (Strongylocentrotus purpuratus) with tube feet extended into water to feed, California

Georgette Douwma / Purple sea urchins, California USA

Sergio Hanquet / Purple sea urchin (Sphaerechinus granularis). Tenerife, Canary Islands.

Sergio Hanquet / Purple sea urchin (Sphaerechinus granularis), three of different colours. Tenerife, Canary Islands.

Sergio Hanquet / Purple sea urchin (Sphaerechinus granularis) mouth and spines, close up. Tenerife, Canary Islands.

Sergio Hanquet / Mass of Purple sea urchins (Sphaerechinus granularis) high numbers may be related reproduction cycle. Tenerife, Canary Islands.

Sergio Hanquet / Purple sea urchins (Sphaerechinus granularis), high numbers may be related reproduction cycle. Tenerife, Canary Islands.

Sergio Hanquet / Purple sea urchin (Sphaerechinus granularis) many on seabed, high numbers may be related reproduction cycle. Tenerife, Canary Islands.