The Immortal Glass Sponges of the Deep

Glass sponges may be the longest-living animals on Earth, with some individuals estimated to be 15,000 years old. These fragile creatures build skeletons from actual silica, the same material used to make glass.

Unlike most animals that rely on calcium, these deep-sea sponges construct intricate frameworks from silica extracted from seawater. Because they grow incredibly slowly in the cold, stable environment of the deep ocean, they can survive for millennia. Some scientists argue these unique organisms are so biologically distinct from other sponges that they should be classified as an entirely separate branch of life. Their ability to outlive almost any other creature on the planet makes them a true marvel of longevity.