This unique hermit crab has a symbiotic relationship with the coral (Janaria mirabilis). The hydrocoral has taken over the snail shell that the hermit lived in. The coral continues to grow. The hermit crab uses it claw to seal the entrance.
Care should be given due to the fact the coral will continue to grow and the hermit may find himself left upside down if the coral grows in such a way that it flips over easily.