realmonstrosities:

Bubble Corals have modified tentacles that get inflated with water so as to provide light for their symbiotic algae.

At night, the bubbles are deflated to make room for other, more ordinary tentacles that capture prey.

They also have another set of even longer tentacles known as sweepers that are used to attack other corals. Those bubbles need their space, after all.

…Images: Nemo’s great uncle/RevolverOcelot/Bernard DUPONT