Beach Ghost Shrimp, Callichirus islagrande

Thursday, August 20, 2009

Nature Notes
by Bob Thomas

There are many species of critters living along the beach front that are seldom seen, yet there is constant interesting evidence of their presence.

One such example is the beach ghost shrimp, Callichirus islagrande, a burrowing animal that seldom, if ever, exits its tunnels willingly. This species is endemic to the northern Gulf of Mexico and inhabits the high energy foreshore of barrier islands and similar stretches of quartzite sandy beaches.

The principal evidence of their presence are the inch-high turrets, with a three-quarter-inch opening to their system of tunnels into the substrate. Where one is found, others are always present existing as colonies for 100 meters or so parallel to the beach front, and extending out from the low tide mark for a few dozen meters.

They rarely leave their tunnels because they are immediately gobbled up by fish that cruise their habitat.

Beach ghost shrimp spend their time consuming phytoplankton and other organic matter that they filter from water moving into and out of their tunnels. Water moves as a result of the shrimp waving tiny paddles (called pleopods) located underneath their abdomen. The food particles are captured by appendages beneath their thorax (pereopods) and transferred to the mouth. Mating presumably occurs in the tunnels, followed by females brooding their eggs. Clutches are often fertilized by more than one male.

When populations peak, another bit of evidence of their presence is the arching swash lines of fecal pellets that are washed onto the shore by the millions. Their size and color are reminiscent of chocolate sprinkles used on donuts and cupcakes.

Don't bother trying to dig them up with your hands, because they will move deeper into their branched system of tunnels and chambers faster than you can dig. The only way to efficiently collect them is by using an Australian yabby pump, basically a suction tube made of PVC or stainless pipe. Place the tube over the burrow opening, lift the plunger, and you should have a beach ghost shrimp in the tube.

Why the name yabby pump? The Australians have a similar species of ghost shrimp that they call a yabby, and it is a popular fishing bait. They also have an edible crawfish that they call a yabby.

Next time you visit the beach, don't just search for bottlenose dolphins and sharks. Look beneath your feet for unexpected marvels.

Also published in Delta Journal, The Times Picayune, June 15, 2008.

                                      

Beach ghost shrimp, Callichirus islagrande,                                  Beach ghost shrimp burrow openings.
removed from its lair.                                                                 The turrets are typical of openings
Photo by Bob Thomas.                                                            protected from heavy surf.
                                                                                                Photo by Bob Thomas.

                                      

Beach ghost shrimp are colonial and may                                    Patrick Thomas using a yabby pump to
be present by the hundreds.                                                      collect beach ghost shrimp.
Photo by Bob Thomas.                                                             Photo by Bob Thomas.

                                     

When beach ghost shrimp are abundant                                     Close-up of beach ghost shrimp fecal
and the wave dynamics are suitable, the                                    pellets. They resemble chocolate sprinkles.
swash lines on the beach may be composed                               Photo by Bob Thomas.
entirely of their fecal pellets. Fort Morgan, Ala.
Photo by Bob Thomas.