10. Glass Sponge (Anoxycalyx joubini)
The Antarctic glass sponge (Anoxycalyx joubini) is a true elder of the animal kingdom, with some individuals estimated to be several thousand years old. Their remarkable longevity is supported by a unique, silica-based skeletal structure that grows extremely slowly in the icy Antarctic depths.
According to Nature, these sponges are among the longest-living animals known, quietly enduring as living relics of the ancient ocean.