Tag Archives: snails

Ocean ‘jewels’ encompass life stories of amazing snails

Published June 3, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Snail species, or gastropods, are abundant in the waters off Australia. The shell at upper right is from a Conus geographus, a cone snail that can kill a person with its sting. However, the sand-filled shell was indicative that the snail inside was long dead and, therefore, was safe to pick up. ©2017 Susan Scott

BRAMPTON ISLAND, QUEENSLAND, AUSTRALIA >> The combination of afternoon low tides and Cyclone Debbie’s recent stirring up of the ocean floor has sparked a new passion in me: snails.

Like all beach walkers, I’ve always enjoyed finding pretty seashells, and like all biologists, I learned about the animals called mollusks. But never have I seen snails and homes like I have this week.

Australian waters host countless snail species. Really countless. One local book claims that more than 10,000 species live here. Another shell guide reports tens of thousands.

Marine mollusks include octopuses, cuttlefish, squids and sea slugs, but those shell-less creatures don’t leave much of a legacy after they die. What gets us beachcombers excited is finding the jewel-like homes of two-shelled creatures we call clams and oysters (bivalves), and the one-shelled creatures we know as snails (gastropods).

Most people don’t include the word “snail” when talking about a shell they’ve found, but that overlooks the animal that built the stunning piece. Of the billions of empty shells cast ashore on the world’s beaches, each has its own life story.

Most snails begin their lives as tiny hatchlings that swim for days or months before settling on the ocean floor. Soon after, the baby snail’s glands secrete a hard, calcium carbonate covering, the beginning of the adult animal’s shell, around its soft body. As the animal grows, its glands enlarge the shell along its outer edge, often in a spiral.

A snail doesn’t add shell material evenly, but rather lays it down in precise places to create its own species’ shape, thickness, height and diameter. At the same time, the creature’s glands introduce pigments into the calcium carbonate that show up on the shell as spots, lines or other markings unique to the species.

Snails don’t enlarge their shells continuously, but do it in spurts. On some spiral shells you can see growth lines called sutures. In adult snails the inside whorls of broken shells reveal the snail’s nursery and its rooms during adolescence.

Besides being superb architects and sculptors, snails are math geniuses. The complex calculations of depositing each molecule of shell and each speck of color in the precise right place at the precise right time to create a species’ exclusive shell is unfathomable.

During a stretch of bad weather, we parked Honu in a marina, rented a car and drove to central Queensland to see Australia’s sapphire gem fields. The sapphires in the shops were OK, but I didn’t buy any. I prefer jewels made by snails.

Moon snails use stealth in the sand to stalk prey

Published January 28, 2017 in the “Ocean Watch” column, Honolulu Star-Advertiser ©2017 Susan Scott

Moon snails lurk beneath the surface of shallow to deep water, burrowing down as much as 7 inches in the sand. ©2017 Susan Scott

I love moon snail shells. They’re marble smooth, patterned in rays of soft colors, and their whirls are classic. But just because the creatures’ homes look inviting doesn’t mean the animals that built them are. Moon snails are a nightmare on clam street.

Not that we, or their prey, usually see the snails in the water. Even after snorkeling on beaches littered with moon snail shells, I’ve never seen one live. That’s because moon snails skulk underwater below the surface of the sand, sometimes as deep as 7 inches. They’re down there hunting for sand-dwelling clams, mussels and most any shelled animal they can catch, including other moons.

Moon snails, and most others, get around by rippling their muscular foot, an organ beneath them that looks like an oval throw rug. When it senses a potential meal, a moon snail can inflate its foot with sea water to four times its shell volume, throw the front over its head and, well, run.

After the foot encloses its prey, the snail drags it to the sand’s surface and goes to work: Drill, baby, drill. That soft-bodied snails can drill holes in shells is hard to fathom. But those squishy bodies hold an arsenal of daggers and chemical weapons.

Moon and other snails have an extendable flexible snout, like a tiny elephant trunk. At the end is the snail’s mouth containing a tongue lined with sharp, curved teeth.

Often the moon turns its catch so the hinge is closest to its mouth. This may be the handiest way to grip the doomed bivalve, or it may be that drilling the hole directly over the bulk of the soft tissue inside makes for efficient dining.

While the snail hangs on with its foot, it curls its tongue, teeth outward, and pushes and pulls at the site while secreting acid. When it breaks through, the mouth sucks out the prey’s organs.

You can tell a moon snail hole from other drillers, such as drupes, whelks and murexes, because moons’ are countersunk. The empty moon snail shells we find on beaches are particularly attractive because the snails spent their lives plowing through sand, which polished the shell and prevented encrusting organisms from growing on it.

The drilling skill of moon snails, and other drillers, is visible on some beaches, where countless shells bear perfect pukas.

About 250 moon snail species live in shallow to deep waters, from tropics to poles. Hawaii hosts nine species, ranging from one-half to 1-1/2 inches tall. The largest moon snails live on the North American West Coast where they grow 5-1/2 inches tall. The day I find one of those, I’ll be over the moon.

Exhibit reveals distinction, beauty of Niihau shell lei

In the past when someone mentioned Niihau shell lei, I wondered why the shells that washed up on Nii­hau beaches were special. Couldn’t a person find similar shells on other island beaches? Which snail species grew the shells? Are people still making the intricate lei? How can you tell they’re from Niihau?

Last week I got the answers to my questions, and more, in elegant fashion. I visited the Bishop Muse­um’s exhibit “Niihau Shell Lei: Ocean Origins and Living Traditions.”

The shells most prized in Niihau lei come from three minuscule marine mollusks ranging in length from about one-tenth to three-eighths of an inch. Depending on spe­cies, the tiny snails live in the sand or on plants, rocks or other animals near the ocean floor. Some species graze on algae, while others eat bits of dead plants and animals and the droppings of living organisms.

The same snail species that make the shells found on Niihau beaches also live in tide pools and shoreward areas of other Hawaiian Islands, as well as in shallow waters throughout the Pacific and Indian oceans.

After the snails die, waves and currents carry some of the empty shells to shore.

In a brochure, the Bishop Museum calls these and other micro-mollusks (shells two-fifths of an inch long or less) barometers of the sea because the creatures are supersensitive to changes in their environment. The snails’ scarcity or abundance gives researchers information about the condition of local waters.

The Pacific Ocean is apparently healthy around Nii­hau because the shells gathered for lei there are considered more durable, produce vivid colors and have shinier surfaces than those of the same species found on other islands.

Another reason Niihau shells are prized is because they’re from Niihau, an island rich in history, tradition and mystique. Nicknamed the “Forbidden Island,” Nii­hau is about 18 miles long by 3 to 6 miles wide and privately owned.

Due to a lack of jobs, Nii­hau’s population has been steadily declining (less than 70 in 2009) with many former residents now living and working on Kauai.

Some lei artists continue to create stunning lei from shells found on Niihau beaches. The lei makers, often called stringers, sort the breakable, barely visible shells by species, size and color, and use an awl-like tool to remove grains of sand from the openings. Using the same tool to make holes in the shells, the artists string, knot and tie the shells into their own unique shapes and patterns.

Prices for Niihau shell lei range from $100 to $30,000.

To preserve the integrity of this art form, Hawaii legislators passed a law in 2004 requiring that anything described as a Niihau shell lei must have 80 percent of its shells from Niihau and must be made in Hawaii.

You can learn more about this unique blend of art, culture and marine life at www.niihauheritage.org/index.html.

What’s so special about Niihau shell lei? My visit to the Bishop Museum made it clear.

The shell show runs through Jan. 27.

Marine biologist Susan Scott writes the newspaper column, “Ocean
Watch”, for the Honolulu Star-Advertiser, www.staradvertiser.com

©2013 Susan Scott