Reef & Rainforest
Commensalism, living together with another organism to the advantage of both, is common amongst many palaemonid shrimps and many smaller crabs. Certain feather star species and large specimens of Toxic Sea Urchins (Asthenosoma varium) often host numbers of squat lobsters, Coleman or partner shrimps, snapping shrimps (Synapheus sp.), and Zebra Crabs. Porcelain crabs (Neopetrolisthes sp.) live together with certain sea anemonies.
In the day time, reef shrimps and crabs are often hidden away in crevices. Tell-tail antennae waving out from behind a rock advertise a cleaner shrimp waiting for business. A patient diver will not only see the shrimp in action on a fish, but may be visited themselves! Night time brings out large numbers of sponge crabs, anemone crabs, cryptic spider crabs, lobsters and many different Penaeid shrimp species. It's a different world.