Ghost Shrimp
By Dr. Joe Richardson
One of the most abundant invertebrate animals living in Tybee’s beach
is the Ghost Shrimp. But as abundant as they are, chances are that you’ve
never seen one! However, anyone who has walked along the water line
at low tide has most likely seen signs of them. The evidence that you will
see are those small holes in the wet sand, particularly those holes that are
surrounded by small, dark brown “sprinkles.” Now … I bet you know what
I’m talking about.
The hole you see is just the top end of a long open tube/channel that
extends down into the sand and branches many times and may extend down
to five feet or so below the surface. As the open channel extends deeper
below the sand, its diameter increases to about a half an inch. It’s down
inside that branched system of tunnels, deep under the sand’s surface, that
the Ghost Shrimp lives.
A Ghost Shrimp is one of those weird-looking marine animals. It might be
4 or 5 inches long, and is a crustacean more closely related to hermit crabs
than to true shrimps. At its head end, it does have a couple of long claws
with small pincers, and a thin shell (exoskeleton) similar to a regular shrimp.
But after that, the rest of its body is flimsy and soft. So it has very little
physical or structural protection from predators or from drying out. Inside
the thin, transparent covering of its abdomen, there is little muscle and 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
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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
and body to push water back up its tunnel. You may well have seen water
gurgling up out of these holes as you walked in the wet sand. One of the
reasons it pumps water back up is to clean out its burrows, so often you
might notice a ring of tiny, dark-brown, cylindrical “sprinkles” around its
hole. And as you guessed, those are its fecal pellets that settle out of the
flushed water.
So, although it’s rare to see a Ghost Shrimp, you can tell by the number
of their holes in the wet sand that they are an abundant member of our
sandy beach shoreline marine community. Because they produce lots of
slime that glues mud and sand grains together to make the walls of their
tubes and burrows, their tunnels are fairly substantial in structure. In fact, in
old shorelines that have since become hardened or fossilized dry land, the
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 35+ 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.
Beach Walks
with Dr. Joe
/(www.TybeeBeachEcology.com)