Olga Kamenskaya / Endemic freshwater sponge (Lubomirskia baicalensis), Lake Baikal, Siberia, Russia. October.

Olga Kamenskaya / Endemic sponge (Lubomirskia baicalensis), Lake Baikal, Siberia, Russia. September 2013

Claudio Contreras / Giant barrel sponge (Xestospongia muta) Cozumel Reefs National Park, Cozumel Island, Caribbean Sea, Mexico, February

Olga Kamenskaya / Diver with Baikal sponges (Lubomirskia baicalensis). Lake Baikal, Russia, March 2007. Model released.

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

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

Alex Mustard / School of Bludger trevally (Carangoides gymnosthethus) throng over a coral reef, with a giant barrel sponge (Xestospongia muta). Misool, Raja Ampat, West Papua, Indonesia. Misool Marine Protected Area...

Alex Mustard / West Indian spider crab (Mithrax spinosissimus) shelter in a giant barrel sponge (Xestospongia muta) on a coral reef. Jardines de la Reina, Gardens of the Queen National Park, Cuba. Caribbean Sea.

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

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...