Alex Mustard / Portrait of Blacktip grouper (Epinephelus fasciatus) resting in Barrel sponge (Xestospongia testudinaria) Mabul Island, Sabah, Borneo, Malaysia. Sulawesi Sea.

Georgette Douwma / Barrel Sponge (Xestospongia testudinaria) on coral reef with soft corals (Scleronephthya sp), gorgonian and Lyretail anthias (Pseudanthias squamipinnis). Komodo National Park, Indonesia.

Juergen Freund / Massive barrel sponge (Xestospongia testudinaria) and diver. Tubbataha Reef National Marine Park, Palawan, Philippines, April 2009. Model released.

Juergen Freund / Giant barrel sponge (Xestospongia testudinaria) studded with crinoids / featherstars with diver in the background, Kimbe Bay, West New Britain, Papua New Guinea.

Michele Westmorland / Diver at healthy reef system with large Barrel sponge (Xestospongia testudinaria) covered with crinoids / feather stars (Oxycomanthus bennetti). Mulloway's Reef, Tufi, Papua New Guinea, model released...

Fred Bavendam / Giant Barrel Sponge (Xestospongia testudinaria) spawning, Bali, Indonesia

Carine Schrurs / Coral reef scenic with Barrel sponges {Xestospongia testudinaria}, Crinoids {Crinoidea}, Anthias fish Batangas, Philippines. Indo-Pacific

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