A hermit crab, sessile on corals, exclusively feeds by feathered antennae.

The hermit crab Paguritta harmsi does not live in mobile shells, but occupies the calcareous tubes of the coral epibiont Spirobranchus giganteus (Polychaeta). Feathered (second) antennae are an unique adaptation to this sessile mode of life enabling the crab to utilize plankton carried by the water. The mode of filter feeding depends on the speed of water current: during stagnation of water the antennae are continuously moved fore- and backwards, during flowing water they are kept perpendicularly to the current forming a sieve. P. harmsi represents one more example to establish a specialized ecological niche in the highly complex ecosystem coral reef.