Photo by Cassie Criffin 



The faded chip of a seashell rolls ashore with 

 the waves. Most beachcombers pass it by. 



Not Lundie Spence. For her, that castaway 

 shell is even more valuable than a perfect spec- 

 imen for a showcase collection. 



She knows it has a story to tell, and she's 

 detective enough to uncover it. 



Spence, Sea Grant's marine education spe- 

 cialist, examines a discarded shell the way she 

 would a deserted house, looking for clues of 

 the inhabitant's past. 



She points to a blemish in a whelk. "It sort of 

 looks like a scar. Maybe a blue crab tried to 

 crack the shell when it was much smaller," she 

 says. 



Instead of stalking the state's coastal waters 

 for live whelks, snails and clams, Spence is 

 content to gather up their remains or just to 

 observe the animals. 



"Some people are only interested in a whole 

 shell," Spence says. "But you can pick up pieces 

 of shells and try to identify what that shell 

 was — by the shape, texture, thickness and 

 curves. 



"Then you can say, 'Yeah, at one time, this 

 spiral was part of a whelk,' or 'This purple 

 fragment was a little clam,' or 'This orange 

 cup-like shell is what's left of a giant horse 

 conch,' " Spence says. 



Seashells are homes for a phylum of soft- 

 bodied animals called mollusks. 



Gastropods and bivalves make up most of 

 the mollusks. Gastropods usually have a single 

 spiral- or cone-shaped shell. Bivalves have two 

 shells hinged tightly together with strong mus- 

 cles. Other mollusks, such as the squid and 

 octopus, don't have external shells. 



Each mollusk builds its own shell. In its larval 

 stage, the animal secretes a material that hard- 

 ens when combined with minerals from the 

 seawater. 



The genetics of each species determines 

 what its shell will look like — whether a whelk 

 shell curves to the left or right and whether a 

 clam shell is smooth or has ridges. The minerals 

 in the water affect the color of the shells. 



Sometimes, if you look closely at a shell, you 

 can figure out how the animal died. And more 

 than likely, you'll find evidence of foul play. 



For example, a clam shell with a round hole 

 near its hinge met its demise in an encounter 

 with a moon snail. After attaching itself to the 

 clam, the moon snail spit out acids that cor- 

 roded the shell. Then, it used its digestive 

 enzymes to weaken the clam. 



Clams often fall victim to another killer — the 

 whelk. These slow-moving hunters inch along 

 under the sand, their siphons sniffing out 

 unsuspecting clams. The whelk grasps its 

 strong foot around the clam and pries it open. 



But even the whelk is not safe. A shell perfo- 

 rated by hundreds of tiny holes was probably 

 the victim of an orange-colored boring sponge. 

 The sponge attaches itself to shells and secretes 

 an acid that eats through the shell. 



Box crabs also prey on whelks, opening a 

 hole in the shell with a can opener-like claw. 



With predators like that, shells don't stand 

 much of a chance. 



If the animal isn't devoured by one of its own 

 kind, it's likely to come up against a human. 



That's why Spence urges folks to leave live 

 shells alone. You can learn a lot about the ani- 

 mal's behavior just by watching. 



Photo by Scott Taylor 



