Glass sponges, or hexactinellids, belong to the phylum Porifera. These animals are common only in the deep ocean. Their tissues contain glass-like structural particles made of silica. The many tiny siliceous elements of a glass sponge’s skeleton are called “spicules.” Unlike most sponges, glass sponges produce extremely large spicules that fuse together in beautiful patterns to form a “glass house”; a complex skeleton that will often remain intact even after the sponge itself dies.
The skeleton of the glass sponge together with various chemicals provide defense against many predators. Some starfish, however, are known to feed on glass sponges.
Glass sponges live attached to hard surfaces and consume small bacteria and plankton that they filter from the surrounding water.
The most famous glass sponge is a species of Euplectella, known as the “Venus flower basket,” which builds its skeleton in a way that entraps a certain species of shrimp inside.