This gland produces an acidic secretion that can eat through the special protein cover on most clams. Following the penetration of the outer protein layer the acid can also help dissolve the calcium in the shell. This group of teeth scrapes away some of the protein fibers and calcium which make up the shell. The process can take a while. The cycle of scraping with the radula for a minute, followed by 30 to 40 minutes of acid secretion, continues as the shell is demineralized.
Snails can penetrate a shell as thick as five millimeters.
The snail completes its work by extending its proboscis through the hole, using the radula to tear up the tissues and ingesting the particles of meat. Another predator - sea stars Another creature that preys on clams is the sea star, also known as the starfish. Sea stars that feed on clams place their mouth above the edge of the clam that opens. They extend their arms around the clam, attach their tube feet, and then slowly exert pressure to open the clam up. The tube feet of sea stars are like suction cups.