Pascal Kobeh / Barrel sponge (Xestospongia testudinaria) covered with Lampert's sea cucumbers (Synaptula lamperti). Crinoids and Feather stars (Crinozoa) also on Sponge. Jewel fairy basslets (Pseudanthias squami...

Pascal Kobeh / Squat lobster (Lauriea siagiani) living commensally on Barrel sponge (Xestospongia testudinaria). Flores Sea, Indonesia.

Magnus Lundgren / Wild Wonders of China / Giant barrel sponge (Xestospongia testudinaria) Xiaoliuqiu Island, Taiwan

Gary Bell/ Oceanwide / Feather Star (Oxycomanthus sp) group on Giant Barrel Sponge (Xestospongia testudinaria) in coral reef, Great Barrier Reef, Australia

Gary Bell/ Oceanwide / Feather Star (Oxycomanthus sp) group on Giant Barrel Sponge (Xestospongia testudinaria) in coral reef, Great Barrier Reef, Australia

Shane Gross / Map puffer fish (Arothron mappa) hiding inside a barrel sponge, off Flores, Indonesia.

Alex Mustard / Schools of baitfish including Cardinalfish (Apogon spp) and Silversides (Atherinidae) mass on a coral reef, with Giant barrel sponge (Xestospongia sp.) and predatory coral grouper (Cephalopholis minia...

Alex Mustard / A threadfin hawkfish (Cirrhitichthys aprinus) on a barrel sponge. Bitung, North Sulawesi, Indonesia. Lembeh Strait, Molucca Sea.

Georgette Douwma / Barrel sponge (Xestospongia testudinaria) and gorgonian coral. West Papua, Indonesia.

Linda Pitkin / Green finger sponge (Iotrochota birotulata), with colonies of Golden zoanthids (Parazoanthus swiftii), on Netted barrel sponge (Verongula gigantea), on coral reef Klein Bonaire, Bonaire, Leeward Antil...

Alex Mustard / Dwarf hawkfish (Cirrhitichthys falco) perched on the ridges of a barrel sponge. Anilao, Batangas, Luzon, Philippines. Verde Island Passages, Tropical West Pacific Ocean.

Franco Banfi / Squat lobster (Lauriea siagiani) on Sponge (Xestospongia), Cabilao House Reef, Cabilao Island, Bohol, Central Visayas, Philippines, Pacific Ocean.