Barrel Sponge Xestospongia testudinaria
Giant barrel sponges grow large enough to fit a person inside. Their hard surface is deeply ridged, but their rim is thin and delicate. The barrel sponge belongs to the Demospongiae, the largest class of sponges, containing about 95 percent of sponge species. The skeleton of sponges in this class is made from both scattered spicules of silica and organic collagen called spongin. An almost identical barrel sponge, Xestospongia muta, occurs in the Caribbean.
- Class Demospongiae
- Height Up to 6 ft (2 m)
- Depth 6–165 ft (2–50 m)
- Habitat Coral reefs
- Distribution Tropical waters of western Pacific