How a Pearl is Made

I am not one to wear pearls, nor do I own any, but I am intrigued by how they are made. I’ve always been under the assumption that they’re made exclusively by clams. Well, we know what happens when we assume.

No pearl inside this clam (a species called a buttercup lucine)!

As it turns out, ANY bivalve can produce a pearl. And ironically, they are actually the product of an irritant inside a bivalve’s shell. If some matter of debris, like a grain of sand or a parasite, gets caught inside the shell and the mollusk cannot flush it out, it’s like us getting a splinter. Since they don’t have tweezers of their own, they coat the foreign object in the same material used to build their shells. Eventually it forms a pearl.

But not all pearls are created equal. Mussels, oysters, and clams are the only species of bivalves that yield the prized pearls. They produce nacre, also known as the mother-of-pearl. Therefore, if you’re looking for jewelry, seek out one of those guys.

However, most pearls harvested and sold today are not actually natural pearls. Instead, they are cultured pearls cultivated by oyster farmers. In this case the “farmer” raises the oyster for about three years. Once they are mature enough, an irritant is implanted inside the shell. The mollusk is then returned to the water for the next two to five years as the pearl is formed. Later the pearl is harvested and sold. Interestingly, naturally occurring pearls are very rare; in wild oysters, only about 1 in 10,000 will produce a pearl.

Life of a Seashell

While collecting shells on the shore, it’s easy to forget that those shells were once homes to living creatures. The small, soft-bodied creatures who once inhabited the shells, called mollusks, include scallops, clams, whelks, conches, and more (note: there are other mollusks that do not have shells, including octopuses and squid).

When these creatures emerge from their eggs in the ocean, they are tiny, free-swimming larvae. Within a few days they begin to build their shells. These shells are built layer by layer throughout their lives. The shells are built by a part of the mollusk’s body called a mantle. The mantle builds the shell using salt and chemicals from the ocean, mixed with special chemical proteins in their own bodies. As the body grows, the shell is enlarged and extended, and new layers of shell are added (unlike hermit crabs who move into larger and larger shells as they grow, mollusks’ shells grow with them). Not only that, but if part of the shell is damaged, mollusks can make repairs!

And similar to other creatures that leave a skeleton behind when they die, shelled mollusks leave behind their shells. Eventually those shells wash up on the beach. But the story doesn’t end there. The shells are still important. They can be used by hermit crabs or as shelter for young fish. Some birds even use shells to build their nests. Shells that remain on shore can help to stabilize and anchor sand on the beach. In addition, as the shells are crushed by waves and other forces, they become sand themselves! Further, as they break down, seashells provide nutrients for sand-dwelling organisms. Thus, as I have just learned, shells should be left on the beach!


I will admit that, until very recently, whenever someone said “scallops” I immediately thought of a delicious meal. But as is often the case, with a closer look and a little research, I now have a new appreciation for those bivalve mollusks.

Let’s start with the fact that I didn’t even know what I was seeing on the beach was a scallop in the first place. But yes, scallops are those fan-shaped, corrugated shells. The corrugations, called ribs, make the shell strong and hard to break. In addition, the corrugations make the shells great places for other plants and animals to grow, which in turn helps to camouflage the scallop. If the camouflage doesn’t work and a predator nears, though, scallops will swim away! No kidding. By clapping their shells together, scallops can actually move quite quickly!

This scallop was very much alive (clapping its shells together!) and was returned to the ocean.

The scallops open and close their hinged shells using the whitish muscle inside the shell (visible in the photo). That muscle, by the way, is the part harvested for the aforementioned meal! There’s also a bright orange section inside the shell, called a coral. Scallops eat plankton; when water enters their shells, mucus traps the small organisms and cilia moves the meal to the scallop’s mouth. But perhaps the best scallop fact of all is that they have up to 200 eyes! They line the edge of their mantle and can be black to bright blue (look closely at the picture…there they are!). The pupils of these eyes dilate in response to light and the retinas focus light, but scientists are still learning about the dynamics of scallop eyes.

So now the question is, what will you think of the next time you hear someone say, “scallops”?


Sand Dollars

Most people probably think of sand dollars as treasures found on a beach. They are usually white with an amazing and intricate five-point shape on the back that looks like petals of a flower (also known as a petaloid ambulacra). These white sand dollars are no longer alive. Which brings up the question, what are they like when they are alive?

Living sand dollars, relatives of sea stars and sea urchins, dwell on the seafloor and are greyish purple. They are covered in tiny hairs and spines called cilia that serve a number of purposes. For starters, sand dollars use the cilia to move along the sea floor – who knew that a sand dollar had a form of locomotion! Not only that, but sand dollars only lie flat on the bottom of the ocean when the water is rough or fast moving. Most of the time they use the cilia to stand themselves up on edge, with one end partly buried in the sand. The spines on the upper half of a sand dollar also serve as gills.

But wait, there’s more. The cilia are used to transport food particles towards the sand dollar’s mouth on the bottom, center of its body. They are considered carnivores because they eat plankton, crab larvae, and small bits of animals, in addition to algae. Inside the sand dollar’s mouth, there’s a jaw with five teethlike sections, used to grind up their food! These creatures chew for up to 15 minutes before swallowing. Food takes up to two days to fully digest.

When you find a sand dollar on the beach, there are probably others nearby because, when alive, sand dollars live in colonies! Whether or not this makes them “social” creatures is up for debate, but they do gather together in groups that can exceed 600 sand dollars in a square yard. These packed crowds may aid in reproduction because sand dollars don’t mate in a traditional sense. Instead, both males and females “broadcast” sperm and eggs into the water. The more closely packed they are, the higher the chance sperm and eggs will meet.

So the next time you find the exoskeleton of a sand dollar, it is indeed a treasure but one with a long and interesting life history before it landed at your feet!


Puss Caterpillar

This caterpillar was given its name because of its resemblance to a cuddly cat. It is furry and only about an inch long, giving it a mostly adorable appearance. But don’t touch it! The furry puss caterpillar is one of the deadliest caterpillars in the United States.

Photo by Brett Hondow, 2013

Their outer furry hairs hide tiny, toxic spines. If you come into contact with them, the spines will stick in your skin. The stings can be incredibly painful, like a bee sting, but worse. And, the pain worsens over times and radiates through the body. Some people have reported that the stings make their bones hurt. Luckily, most people recover by removing the spines, then treating with ice and antihistamines.

Now the story of the puss caterpillar doesn’t end there. This furry, adorable, toxic caterpillar turns into a poop flinging moth. You can’t make this stuff up. As adults, the puss caterpillars turn into flannel moths. According to National Geographic, female flannel moths fling poop away from their bodies. Scientists believe the reason for this is to keep away parasites that are attracted to poop and may harm the caterpillars.


I’ve been thinking a lot about water lately. Maybe it’s because we didn’t have much precipitation for months and months and now the snow just keeps coming. Or maybe it’s because more than 70% of Earth is covered in it, but only 3% of that is freshwater. Or maybe it’s because I just finished a month of brainstorming picture book ideas (Storystorm!) and so my “idea brain” is on full alert. But no matter, today my musings are about water.

The water cycle is an amazing process, but that’s not what’s been on my brain. Instead, I’ve been thinking about all the places we might find water and all the forms it takes. Let’s start easy: water is rain, snow, and sleet; oceans, lakes, and rivers are water. But water is also the puddle we slosh through, on the hill we sled down, and the ice we slide on. It’s the pool we swim in, the ice cubes in our drinks, and the shower we take.

But if we dig deeper, there’s so much more. Like a dew drop reflecting the sun. It can take the form of team rising off a hot cup of tea. It’s evident in the exhalation of whale. It’s curlicue icicles and glaciers and permafrost. It’s geysers and hot springs and ancient aquifers of water that rained on the backs of dinosaurs. Water takes the form of fog and clouds and humidity. It’s the sweat on our skin. When we see our breath, we’re seeing the moisture from our warm breath condense into tiny visible droplets in the cool air. The adult body itself is actually 60% water!

So I challenge you. As you go about your day, think about water. Notice water all around you, both visible and hidden. Think about all the forms it takes. Does it make you think differently about water? I hope so!


Ode to a Tree

On an Open Space path I’ve walked many times there are many tall cottonwood trees along a part of the creek. One in particular has been a favorite – an enormous, glorious tree that somehow seemed larger and more majestic than the rest. But it literally fell victim to the fierce winds that ripped through the region weeks ago. On a recent walk, I found it laying on its side. The loss of this tree has stuck with me for some reason, though the objective side of me knows this is just part of the cycle. Still.

Cottonwoods are the largest broadleaf trees in Colorado and the only ones to grow on the plains. Above ground, their branches can reach close to 200 feet into the sky. Below ground, their sprawling roots reduce erosion and slow floodwater. Of course, the trees also provide a habitat for many local species.

They get their name from their seeds that look like snow. Often in the springtime, a breeze makes it look like flakes are falling and the ground below cottonwoods looks like it’s blanketed in snow. Once sprouted, the trees will grow and live for up to a hundred years. “My” tree was certainly that old, and I couldn’t help but wonder about the changes it had witnessed in those years. Now it will spend the next 100 years returning to the earth, continuing to provide for the surrounding environment.

Rainbow Eucalyptus

Behold the rainbow eucalyptus tree. These trees are native to Philippines, Indonesia, and Papua New Guinea, and were brought to the Hawaiian islands in the early part of the 20th century. They are massive trees found in tropical rainforests that get a lot of rain, growing to 250 feet tall. But what makes them stand out is their bark.

Most trees I’m familiar with have brown trunks that range from reddish to dark brown; and of course, there are birch and aspen trees with white bark. The rainbow eucalyptus though, look like an artist’s canvas or something out of a fairy tale. The bark of the eucalyptus is full of bright, multi-colored patterns. No two are the same.

That, of course, begs the question, why are they so colorful? It turns out that as a tree sheds its bark (throughout the year), it reveals a bright green layer underneath. Then, air and sunlight react with the bark. This reaction causes the bark to change to different shades of green, orange, blue, purple, and red. Since the tree doesn’t shed all at the same time, the colors on the bark are constantly changing as exposed areas begin to age. The patterns never repeat.

National Penguin Awareness Day

Photo by John Salatas

This coming Thursday, January 20 is National Penguin Awareness Day (not to be confused with World Penguin Day in April), when penguins get a day in the spotlight. And what’s not to love? These flightless sea birds are adorable both as chicks and as adults. They waddle when they walk with their stubby wings awkwardly splayed out from their sides. And then there are the heartwarming images of male Emperor penguins huddled together against the frigid Antarctic cold with an egg nestled on top of their feet.

Depending on who you talk to, there are 17-20 different species of penguins, all in the southern hemisphere. Many of these species live in Antarctica, but not all of them live in cold climates. Some live in much more hospitable places like the Galapagos, South America, Africa, New Zealand, and Australia.

What penguins lack in agility on land, they more than make up for in the ocean. In fact, in the ocean they are expert swimmers, some reaching speeds of over 20 miles per hour. They can even leap out of the water like a dolphin as they swim! Penguins spend most of their lives in the water, which is why they sport the black and white tuxedo. When they are in the water, from above their black backs blend them into the murky depths. From below, a penguin’s white belly camouflages them against the bright sky.

The purpose of National Penguin Awareness Day is a day to bring attention to the environmental issues that penguins face (2/3 are listed as threatened), and to promote conservation and research. Learn more at Penguins International to see how you can help!


My new favorite bird is the myna – they are raucous and beautiful and apparently very adaptable. My love for these birds began with a tree in Hawaii. Every night, a huge flock that probably numbered into the hundreds, returned to the same tree. Over the course of an hour at sunset, they settled in and chattered away (loudly). And then, almost as if one of the mama birds said, “Hey, hush up now, it’s bedtime,” they’d fall silent. The same thing happened in reverse in the morning. At dawn, they’d slowly begin to chatter until it because a boisterous chorus. Then, one by one they’d fly away for the day.

Photo by Afsarnayakkan, 2017

I’ve since learned that they are actually an invasive species in many parts of the world, including Hawaii. But It’s not their fault they were introduced to the islands in the mid-1800s to control cutworm moths and they thrived. Today they are seen as naughty, loud, and quarrelsome. Some compare them to flying rats. They also compete with native species.

Still, my affection for them has not changed. They are a hardy and adaptable species. They mate for life with one partner. And their chatter is lovely.