Banded tulips are not spring flowers. They are marine snails! Their smooth shells, that may grow to as much as four inches long, are easy to identify. They are marbleized white and brown, with 4-8 distinct brown lines banding the shells; they are home to black snails. The shells are the snails’ protection; when threatened they pull their soft body into the shell. They even have a horny plate on their foot that acts as a door. This foot is also how they move around on the seafloor (when the “door” is open and the coast is clear!).
Photo Credit: NURC/UNCW and NOAA/FGBNMS.
And beautiful though they may be, these snails are ruthless carnivores – like the wolf in sheep’s clothing of the marine world. They rest in grass flats or on the sandy seafloor, waiting for their next victim. These predator snails will eat smaller bivalves, tube worms, carrion, and other snails. To do this, a snail uses its radula (another new word!). This is akin to a toothed tongue that can bore a hole through the shell of prey. Then the snail inserts its radula into the hole to scrape off the soft contents inside the prey shell and draw the food to its mouth. Kind of like a big straw – slurp!
Aside from the way they get their meals, banded tulips are like other snails. They are gastropods (snails and slugs) in the family of mollusks, that have a shell and a single muscular foot. The banded tulips have two tentacles with and eye at the base. And of course, banded tulips have that ever-useful radula!
Barnacles are often thought of as crusty little creatures that wreak havoc on boat and ships. While that is true, there is so much more to the story. Of course there is. This should not be surprising to me. Let’s start with the fact that there are more than 1,400 species of barnacles in the world. Acorn barnacles are the most common. All barnacles are crustaceans that live in busy waters, generally intertidal zones and underwater volcanoes. But unlike other crustaceans they are sensile (new word!). They cannot move.
Acorn barnacles attached to a scallop shell.
They cannot move because they are literally cemented to their host, be it a boat, piling, buoy, rock, or other sea creature. Acorn barnacles start life as free-swimming larvae. When it’s time for them to settle, they use their first antennae to glue their heads to a hard surface (and yes, they spend the rest of their lives head down, feet up). These first antennae have cement glands that produce a fast-curing cement. Once attached, they begin their metamorphoses and build cone-shaped shells around themselves. These shells are equipped with trapdoors that open when the barnacles are covered in water and close to conserve moisture when the tide it out.
As sensile creatures, the question becomes, how do barnacles eat and reproduce? To eat, they use feather-like appendages called cirri (another new word!). The cirri quickly extend and retract from the shell; when extended they filter the water for microorganisms. The next part is even more interesting. Acorn barnacles are hermaphroditic, but they cannot self-fertilize. And remember, they cannot move. How do they reproduce then? They have the longest male sexual organ (length relative to body size) in the animal world – up to three inches long, which is six times their body size. They use it to pass and receive sperm from their nearby neighbors; fertilized eggs then brood within the barnacles’ hard shells. Meanwhile the sperm-providing appendages dissolve! They grow back the following year.
One last detail. As anyone who has ever tried to remove a barnacle of any species from a boat or other hard surface knows, they are extremely, extremely difficult to detach. This is because barnacles produce one of the most powerful natural glues ever discovered – 5,000 pounds per square inch. It is so powerful that researchers are currently working to figure out how to use it commercially.
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.
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!