Ghost Shrimp Under the Beach
When you walk along the beach during low tide, across the wet sand, one of the things you notice are all the small holes in the sand. Each hole looks like somebody stuck a pencil down into the sand. The hole you see is just the top end of a long open channel that extends down and branches many times and may extend down as deep as five feet. Down inside that branched system of tunnels, deep under the sand’s surface, is where a Ghost Shrimp lives.
Ghost Shrimp are one of the most abundant animals living in Tybee’s beach, but chances are that you’ve never seen one! A Ghost Shrimp is weird looking. It might be 4 or 5 inches long, and is actually related more to hermit crabs than to true shrimps. At its front end, it has a couple of long claws with small pincers, and a thin outer covering (exoskeleton) similar to a regular shrimp. The rest of its body is soft and flimsy. So it has very little protection from predators or from drying out. Through its thin, transparent covering you can see its orange internal organs. With little protective outer covering and weak muscles, it’s no wonder that this soft mushy animal stays deep down in the sand within its burrow.
Within its burrow, a Ghost Shrimp can move around fairly well. When the tide rises and covers its hole, it pulls seawater down for oxygen and food. When the tide goes back out, the Ghost Shrimp will use its paddle-like legs to push water back up its tunnel. Often, during our Tybee Beach Ecology Trips, we will see water gurgling up out of these holes while walking across the wet sand. By pushing water back up, the Ghost Shrimp cleans out its burrows. You might notice a ring of tiny, dark-brown, cylindrical “sprinkles” around its hole. And yep, as you guessed, those are its fecal pellets that settle out of the flushed water.
Although it’s rare to see a Ghost Shrimp, you can tell by the number of holes in the wet sand that they are an abundant member of our sandy beach shoreline community. Because they produce lots of slime that glues mud and sand together to make the walls of their tubes, their tunnels are fairly substantial in structure. In fact, in old shorelines that have since become hardened or fossilized dry land, Ghost Shrimp burrows are preserved in the resulting rock, and geologists use these “trace fossils” to identify the area as a former shoreline.
Dr. Joe Richardson is a retired marine science professor with 40 years of research and teaching experience along GA and the southeastern coast and Bahamas. Besides research, he conducts Tybee Beach Ecology Trips year round (www.TybeeBeachEcology.com) and frequently posts pictures of what they are finding on his Tybee Beach Ecology Trips facebook page.