Janaria mirabilis is similar in appearance to a colonial coral, but comes from a quite separate group of cnidarians.

[4] A juvenile Janaria mirabilis will settle on a mollusc shell occupied by a hermit crab in the genus Manucomplanus.

Here it buds and grows into a colony, sending out side-branches, and at the same time exuding chemicals which erode the mollusc shell.

Eventually the mollusc shell is dissolved away and the hydrocoral takes up residence on the exposed carapace and abdomen of the crab.

[3] A single hermit crab can carry a mobile home weighing nearly thirty times its own weight.