Hitchin' a ride: scuds, shrimps, and sponges are among the creatures that cling to the horseshoe crab

Natural History, June, 2002 by Dave Grant

Each spring, I look forward to the crabs' arrival from offshore, because they always bring along something new and interesting to show me. Over the years, I have noticed that the most lethargic are likely to have algae and various invertebrates cloaking their shells and eyes, and plenty of mussels entangling their legs and gills. Such a thorough covering on the surface of the crab may cause it more than a little inconvenience, interfering with light detection, movement, and respiration. A thick coating of tagalongs seems to presage the demise of the crab. This and a certain sluggishness are clues that they are suffering and probably won't survive another season.

I always peel off the growth from the eyes, legs, and gills of heavily infested crabs, but my efforts probably don't help them for long. They struggle on, ambling off into deeper water and vanishing beneath an ever thickening blanket of bryozoans, barnacles, and whatever else issues from Triton's wreathed horn.

Perhaps, like their human counterparts, these old soldiers never die, they just fade away.

Dave Grant is the director of the Ocean Institute of Brookdale Community College in New Jersey and a field-trip leader for the American Littoral Society at Sandy Hook. This article is adapted from his chapter in Limulus in the Limelight: A Species 350 Million Years in the Making and in Peril? edited by John T. Tanacredi (Kluwer Academic/Plenum, 2001).