Oceanography/holes in the front of shells
Mark N wrote at 2013-11-20 21:00:54
These holes are made by mollusks drilling their way into the shell. The hole in your photo was made by an octopus drilling it's way into the cockle using a special mouthpart called a radula. It can take up to three hours for it drill it's way in. Then it injects a neurotoxin causing the prey a quick but convulsive death. The shell can then be opened. It's worth looking on the beach for these cockle shells and noting the location of the drill hole. It is often right over the muscle that keeps the cockle closed.
Whelks do this too, as do many other gastropods. Whelks tend to soften the drill site with acid secretions and enzymes which soften the shell. Once inside they inject digestive saliva which liquefies the prey. The Whelk can then slurp up the contents.