Coleman’s Urchin Shrimp

Coleman’s Urchin Shrimp have evolved to have coloration and patterning that matches their normal host urchins. This is important for allowing them to blend in, helping them avoid visual detection by predators. However, if they are found by a predator, their second line of defense is the venomous spines of the host urchin which can inflict a nasty sting to would-be attackers. The shrimp reside on an area of the urchin’s test (shell) which is cleared of spines, presumably by the shrimp themselves – it is theorized that the shrimp clear an area of the host urchin’s spines, but the behavior of clearing the spines has not been observed. Coleman’s Urchin Shrimp have been found to remain on the same area, devoid of spines, for long periods of time without moving from their chosen position. They have not been found to harm or help the host in any way, indicating that their relationship is an example of commensalism. The shrimp likely feed on any foods that happen to pass them by, potentially feeding on some of the host urchin’s scraps.