SHELL SEEKER: Shark eye with necklaces
At the end of my favorite shelling beach in Cape May, New Jersey, there was
a little man-made jetty. Boulders were strategically placed to build up an
area of beach eroded by a hurricane. It was there that I witnessed
perplexing sea gull behavior. At low tide the gulls would swoop down and
grab something off the beach. Then they would fly over to the jetty,
hovering at just the right height, and let their parcel drop to its doom,
crashing against the rocks. Then, once again, the gull would swoop down and
make a pass at the sandy area adjacent to the rocks, grab its prey and
devour it on the spot or move to higher ground if harassed by fellow gulls
anxious to share their meal.
As always, I looked to by grandmother for an explanation for this bizarre
behavior. She took me by the hand and we walked over to the jetty covered
with “shell bones,” many of which were bleached white by the sun. She
explained that the shark eye or moon shell as it is called by some, was a
favorite delicacy for the gulls and that the “rock dropping” exercise made
it possible for them to obtain the “meat” inside the shell.
The Neverita duplicata is found on sandy shores just below the low
tide-line. It is shaped like a globe, has four to five whorls, and is
generally grayish brown in color. There is a bluish dot in the center of the
top-side of the shell which resembles the iris of an eye – hence its name.
They are a flattened shell and wider than they are tall. Shark eyes are
found from the New England states to Florida and other states along the Gulf
Shark eyes are predatory, with bivalves providing the mainstay of their
diet. Once prey is discovered in the sand, the snail wraps its foot around
the prey and begins drilling a circular hole into the shell, allowing the
soft tissue within to be sucked out and eaten. Secretions from an accessory
boring organ appear to soften the shell of the prey. The boring process is
very slow, taking from several hours to a day or two. One of the snail’s
favorite foods is the coquina clam.
Shark eyes are a type of moon shell. Moon shells are found in all of the
seas of the world and can grow up to three inches in diameter. The living
snail is amazing looking, with a foot that extends out around the entire
shell. This flattened pad of flesh is the animal’s means of locomotion.
Flesh from the top of the foot actually folds back over the head, serving as
protection as the foot drags the body through the sand. Their
well-developed burrowing ability contributes to their survival.
Female moon snails attach their eggs to necklaces or “sand collars,”
circular masses of sand grains stuck together. The eggs are laid in a
sticky mass of clear jelly substance which is molded over the shell, giving
it the shape of a collar. The mucus is rubber-like while in the water but
when it gets onshore it becomes dry and brittle. The sand falls off at the
hatching time and the eggs become visible.