Moon Snail Egg Collars
During the early spring, beachcombers on Tybee are likely to come across a
number of interesting and sometimes weird objects. Some of these things
and animals have washed ashore from deep offshore reefs, or they may
have been carried to our area by offshore currents from far away locations.
Other objects are actually generated by local nearshore animals, but because
they are produced during a particular phase of the animal’s life history, the
objects are only found infrequently and only during certain seasons.
A good example of this is a Moon Snail egg collar. During early spring, it’s
not uncommon for me to receive a picture of one of these that someone
has seen on the beach with the question, “What is this?” The Moon Snail
(also called a shark eye snail) is one of our common gastropods (snails) that
burrows through the sand an inch or so below the surface anywhere from
mid-tide level on the beach out into the shallow surf zone. Once you learn
to recognize the shallow furrow and wide bump in the sand caused by their
burrowing activity, you can find them in the wet sand during low tide. They
are actually hunting for Coquinas and other clam-like mollusks to eat.
As is the situation with many snails, when it’s time to reproduce, the Moon
Snail manufactures a structure known as an egg case that contains its
fertilized eggs. Inside the protection of the egg case, the new embryos
gradually develop into baby snails before they hatch. The Moon Snail’s egg
26 TYBEE BEACHCOMBER | MARCH 2018
By Dr. Joe Richardson
case is sometimes called an “egg case collar” or “sand collar” because it
is shaped like a shirt collar or a wide funnel. Structurally, the collar is like a
sandwich with a layer of small eggs/embryos on the inside and thin layers
of sand on the outsides. The inner layer is actually composed of many small
compartments that contain the developing baby snails.
If you’ve ever handled a Moon Snail or watched one crawling around in
a bucket of sea water, you know that they produce lots of slime. They
constantly produce the slime because it helps them when plowing through
the sand. They also use this slime to help glue together the sand grains that
form the outer sand layers of the egg case sand collar. As a result, it’s easy
to see how the shape of the collar fits right around the mama Moon Snail’s
shell.
Moon Snails are one of my favorite snails that we find around here, because
of the way they feed on other mollusks. It’s kind of strange, but I’ll save that
for another date. In the meantime, be on the lookout for their egg case sand
collars in the wet sand or washed up along the high tide line while you are
out walking Tybee’s beach.
Dr. Joe Richardson is a retired marine science professor with 35+ years of
research and teaching experience along GA and the southeastern coast and
Bahamas. Besides research, he conducts Tybee Beach Ecology Trips year
round (www.TybeeBeachEcology.com) and frequently posts pictures of what
they are finding on his Tybee Beach Ecology Trips Facebook page.
Beach Walks
with Dr. Joe
/(www.TybeeBeachEcology.com)