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Blame It On The Moon

Moon snails are prolific killers leaving perfectly circular holes as a calling card.

“Snail.” Perhaps your first thought on hearing that word is of a creature both slow and harmless. If you happen to be a clam or another sea snail, and a moon snail has you in it’s sights, think again! Almost any time you look for shells on the beach, you will find a shell with a neatly drilled, beveled, round hole in it. That hole was made by a predatory moon snail. Yes, predatory. And canabalistic. Moon snails don’t mess around.

This shell itself is fairly familiar. It is round, colorful, and often smooth or shiny when washed up onto the beach. For delicious shelled sea life, that pretty shell may be the last thing they see. The one pictured above is called a “shark’s eye.” Another common moon snail is called “baby’s ear.” There are over 250 species of moon snails, or Naticidae in oceans all around the world.


Moon snails stay shiny because they inflate their bodies with enough seawater to quadruple in size, with the resulting massive “foot” completely engulfing the shell while the snail goes about its business of plowing through the sand in search of prey. Welcome to the dark side of the moon…

Murderous moon snail drills into yummy clams and other snails for delicious sea snacks.
Here is a moon snail in the wild, on the hunt, and looking hungry!

Once a moon snail encounters a clam or a snail  —  even another moon snail  —  it engulfs its prey with that big foot. Once the meal-to-be is captured, the moon snail secretes a substance that softens the hard shell, and then scrapes away shell with its radula. (The radula is a sort of “tongue” covered with lots of “teeth.”) That rasping drill eventually breaks through the shell, and the resulting hole gives the moon snail access to the fleshy animal within. Some digestive enzymes are released, and the moon snail slurps up the partially pre-digested goo. Slurpees of the Sea… Yum!

Moon Snail snack

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The Importance of Being Boring

oyster shell with holes

SO many shells, or parts of shells, that wash up on the beach are pocked-marked with dozens or even hundreds of tiny holes. Where did those holes come from?

Well… AHEM:

Those tiny holes are just the start

Of an empty shell falling apart.

Do you wonder what’s to blame?

A “boring” sponge! Yes, That’s the name.

These sponges are not what you think,

Not like the one by the kitchen sink.

They start off small as small can be,

Filtering food from seawater, you see.

Once settled, these sponges cannot roam.

Those tiny holes — they are their homes.

Too many shells would be around

If boring sponges didn’t break them down.

If a coral reef gets crowded and sick,

Boring sponges settle in quick.

They soon tidy up the place,

Then new corals move into the space.

Too many sponges, that’s not best.

In oyster beds, they are a pest.

(Living oyster shells can crumble;

This makes oyster farmers grumble.)

It’s part of every shell’s life cycle:

Boring sponges do recycle.Snailed-It-Snail-Shell-With-Holes-Pensacole-Beach-FL-WMHoley-Mother-Scallop-with-Coral-WM

So when you see those tiny holes,

It was boring sponges roles!


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Eye? Aye!

horseshoe crab eye close-up

Okay. So, nobody guessed the answer to the daily photo quiz…

It is one of two compound eyes on a horseshoe crab.

Not one of its seven OTHER eyes.

Just to be clear, I should tell you that a horseshoe crab is not really a “crab” at all, at least not in the sense of inclusion in the Crustacean Clubhouse. More closely related to scorpions and spiders, horseshoe crabs are ocean dwelling arthropods.

Walking is its primary means of locomotion, thanks to ten pairs of walking legs, but juveniles will swim, upside-down, by flapping their gills. Perhaps I should mention that horseshoe crabs have “book gills,” six sets of flat sheets of oxygen-exchanging tissue that do, with some imagination, resemble books.

For sustenance, horseshoe crabs will eat worms, algae, mussels, clams, dead fish and other carrion.  They simply crawl over a meal and grind the food into mush betweent the spines on the upper parts of their legs, then shove the resulting glop into their mouths.

horseshoe crab on beach

The “tail” (called a telson) may look scary, but it’s really just a tool, useful for steering and especially for flipping itself back onto its feet if it gets flipped onto its back by surf or some mean ol’ human.

The horseshoe crab is a genuine “blue blood:” its blood cells contain “hemocyanin” with copper, instead of “hemoglobin” with iron. As a result, the blood turns blue instead of red when exposed to oxygen. Immune cells in horseshoe crab blood are so good at detecting and eliminating bad bacteria that they are used to test vaccines and some medical equipment before those things are used on humans.

Okay, okay, back to those eyes. The compound eyes help the horsehoe crab recognize a potential mate. The other seven eyes, scattered around the body, detect changes in light levels, especially moonlight, and also pick up movement. In addition to all those eyes, horseshoe crabs also have light receptors in the tail area.  It seems that when it comes to vision, what they lack in quality is made up for in quantity.




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Michelle Sees Sea Shells

It helps to grow up near the beach. A visit to the seashore and all its treasures are easy to obtain. And there is sometimes that person in the crowd who forgoes the chance to sunbathe and instead wanders off in search of “critters.” That person was always me as a child, net in hand , waist-deep in the water with my toes sliding through the sea grass…and collecting shells!

I kept an aquarium whose occupants never came from a store. I watched the aquarium the way most young people watched TV. I noticed that some sea creatures have species-specific “personalities:”  shrimp make good garbage collectors, blennies are territorial, and snails keep the walls clear of algae. I noticed that a strange little fish that buried itself in the sand during the day came out at night to nosh on its neighbors. (It did not start out looking like a barracuda…).

I spent part of my junior year in college at Duke’s Marine Lab, studying “lower invertebrates,” a group which includes a lot of worms. Years later I went along on about a dozen multi-day school trips to the Georgia coast where I learned more about coastal ecology. Along the way,  I realized that everything that washes up onto the shore has a story to tell.

And now, I want to tell you some of those stories with photos I have taken through a microscope.

Why a microscope? For starters, I have enjoyed the use of a microscope since I was about 8 years old. I looked at lots of things: salt crystals, fly wings, cloth, pond scum with all its microscopic inhabitants… In graduate school, I looked at thin slices of mutant frog embryos. In the Cytogenetics lab where I worked, I looked at chromosomes.

About a year ago, a friend gave me a digital microscope used mainly for industrial purposes, such as scanning micro-circuitry to make precise measurements.  With a brass sleeve fitted onto it so that it could be secured into the heavy base of an old dissecting scope, I grabbed a broken piece of scallop shell to take the microscope for a test drive.

What started as:

Scallop shell on sand. Shells transform under the microscope!



Colorful Scallop Photo
Scallop shell from Pensacola Beach, FL.

Oh.  I mean “OH!!”

When it comes to scallops, ridges have ridges. And with just the right lighting, something wonderful appears.

So began my study of “ugly shells.” I hope you will enjoy, as much as I have, the chance to take a closer look.

Like what you see? Shop The Ugly Shell!


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A Closer Look

I have lived on or near a coast for most of my life, and have always been fascinated by the incredible sea life I’ve encountered both as a scientist and lover of art. With The Ugly Shell I hope to combine my passions, impart some of what I have learned, and urge people to look at life through a new perspective. Let’s take a closer look!