Named because of their transparent bodies, Bay Ghost Shrimp are not actually shrimp at all but more closely related to crabs. They are easily identified by their tapered, segmented bodies which at first glance may seem similar to a scorpion or centipede. These animals grow no larger than about 4 inches (10 cm) in length and have six legs and two claws. One claw is generally bigger than the other, especially on males. This species is a detritivore, or an animal which feeds on decomposing organic matter known as detritus.
Bay Ghost Shrimp burrow under sandy beaches, sometimes digging passages as deep as 4 feet (1.2 m). These tunnels not only provide a safe refuge for the shrimp, but they help infuse the lower sand layers with oxygen, which benefits other species and accelerates the decomposition of organic matter.
The shrimp are often caught and used as bait by anglers. They are also used in home aquariums for cleaning up algae and other organic debris.
Bay Ghost Shrimp are common in mudflats and sandy substrates of beaches, river mouths and estuaries. There are several species of ghost shrimp but Callianassa californiensis is found along the west coast from Alaska to Baja California.