The aptly named Ping-pong tree sponge (Chondrocladia lampadiglobus) is a carnivorous sponge. Those ping-pong ball looking things are covered in tiny spicules which the sponge uses to catch tiny crustaceans.
This animal, the Leafy Seadragon, is a Threatened species. They are threatened by collecting for use in Chinese medicine (and by habitat loss). Just one more example of the beautiful natural world exploited by idiotic traditional Chinese cruelty.