Friend Feature: Gumboot Chiton
Cryptochiton stelleri sneaking stealthily through giant barnacles and shiny, orange sea squirts. Image by Ivar Dolph
Giant Pacific Chiton (Cryptochiton stelleri)
Wait, that’s not a rock
Gumboot chiton moving in on some red algae in an eelgrass meadow. Its eight shell plates are hidden beneath its mantle, but you can almost count them all. Image by Jerry Kirkhart, Flickr Creative Commons
In honor of the last few daytime low tides of the year, we bring you a super stealthy intertidal ninja creature. Okay, it may look like a lump of brownish goo stuck on a rock… but that’s just where it gets interesting! This month’s record-holding Creature Feature has some spectacular bragging rights, including being named after an old fashioned rubber boot. Meet the Giant Pacific chiton, aka the Gumboot chiton.
A different chiton, the lined chiton, Tonicella lineata, has its eight shell plates exposed, like most chitons and unlike the gumboot chiton. Image by Dan Hershman, Flickr Creative Commons
Gumboot chitons are, well, chitons (pronounced kite-ens). They are marine gastropods with eight, overlapping, wing-shaped shells hiding under a thick, bumpy mantle. If you’re thinking that gastro = stomach and pod = foot, so these strangely-shaped snails must slip along on their bellies, you’d be right. Gastropods also include limpets and marine, freshwater, and terrestrial snails and slugs, and are part of the mollusc phylum, like clams, octopus, and cuttlefish.
Their reddish brown color comes from what they eat and what lives on their mantle; red algae. These pigments turn the tissue of their mantle (the thick, leathery skin that covers the shell plates) red. The mantle makes them look a bit squishy, like a giant meatloaf, but try touching one with a wetted finger if you’re lucky enough to spot one in the tidepools despite the cool camo. Not squishy at all.
Why 8 shells in one? The shells can slide over one another, so their coat of armor keeps them safe, yet still capable of yoga postures (they’re flexible). Can’t do those with a snail shell.
And now for the record holding: Giant Pacific chiton are called giants for a reason. At up to 14 inches in length and 4.5 pounds, they are the world’s largest chitons. Yet another world record right here in the Salish Sea!
Vegan mollusc
Note the mouth (bottom), the large yellow foot (center) and the frilly gills (paralleling the foot) that are on the underside of the chiton. Sometimes marine worms or pea crabs can be found nestling in between the red mantle and the yellow foot.
Gumboot chitons feed primarily on algae. This includes red and green seaweeds and kelp (brown algae).
Long rows of teeny teeth make up a radula, used for munching their meals. Radula contain magnetite, an iron-based mineral, which makes it tough enough to scrape algae from rocks and could explain their magnetic personalities. The amazing video below caught the radula at work.
Predators
Giant Pacific chiton predators include Lurid rock snails, sea otters, tidepool sculpins, and humans. Have you tried one? You can tell if a chiton has had a battle with a rock snail if its girdle has any small yellow pits. Humans have used this animal as a traditional food source, and its shell plates have frequently been located at tribal sites. Although they are not predators, sea urchins compete for food and space with the chitons. Can you imagine an epic slow-motion battle between a gumboot chiton and a sea urchin?
Circle of life
A female gumboot chiton releases thousands of tiny eggs into the water. See them in the channel alongside her yellow, muscular foot, and coming out at her tail end. Image courtesy of Bruce Kerwin Photography
Gumboot chitons reproduce once a year in early summer by spawning and casting their eggs and sperm into the water in a free-for-all. Waves break apart the gooey dark green strings of eggs released by the females, and the release of the eggs trigger males to release sperm. After about 2-5 days of floating around, the fertilized eggs hatch into plankton that continue to float for about 20 hours. After enough swimming, they finally settle down and eventually metamorphose into juvenile chitons. Young gumboot chitons are less than 1cm long and are more of a yellow color. They are very slow-growing, but if they make it to adulthood, they are estimated to reach an age of 25 years or older (although not a lot is known about their lifespans). Quite the life!
Homebodies
Giant Pacific chiton live in intertidal areas (up to about 20 meters or 65 feet deep) along the northern Pacific Ocean. Adults don’t move too far, but their young live the life of a drifter. Like other molluscs, their larvae, trochophore larvae to be exact, drift about the ocean with the currents as plankton.
When these larvae elongate and change into juvenile chitons, they leave the life of exotic travelling behind and become homebodies. Gumboot chitons tend to stay within the same 6 square meters or 65 square feet patch of seafloor over an entire year! During the day, they hang out on the undersides of rocks or below the tideline. When the sun goes down, the party is on. They leave the quiet life to forage for food and stir up who knows what kinds of chiton action.
What’s in a name?
A Gumboot chiton slinks through an eelgrass meadow, where it will likely spend its whole year. Photo by Peter Pearsall, USFWS
The giant Pacific chiton’s scientific name Cryptochiton stelleri comes from being so well hidden (cryptic) and also from the German zoologist and botanist George W. Steller. Steller was an explorer on board the ship St. Peter mapping and exploring the seas and lands from Russia to North America in 1741-42. Many of his discoveries were in Alaska, and they included creatures like the Giant Pacific chiton, the Steller’s jay, the Steller’s sea lion, the now-extinct Steller’s sea cow, and the Steller’s eider.
How ironic is it that a creature that moves so little in its lifetime was named after a world explorer? Of course, “discoveries” like these were only new to the explorers. The indigenous peoples in the home turf of the chiton had their own names for them since time immemorial. They were not named after people nor printed in books. They were respectfully harvested and eaten, however. Chiton shells are found in shell middens throughout the Salish Sea.
First Food
Kokwalalwoot, Samish Tribe ancestor, met a surprising future husband while gathering chitons for her tribe in the tidepools of Rosario Beach.
If you ever go to Rosario Beach in Deception Pass, you’ll discover a story pole and a story about a young Samish maiden who meets the man of her dreams under the waves as she is gathering, you guessed it, chitons. Indigenous peoples of the Pacific Northwest have been collecting and eating gumboot chitons for many centuries. Because these chitons grip less tightly to rocks than other chitons, they are easier to collect.
They can be eaten raw, baked, boiled, or cooked on a hot surface. The mantle does not taste so great, so that is discarded while the meat is consumed. They are not as tender as other chitons, but if they are steamed for an extended period of time (and if they are slathered in some scrumptious animal fat), they get tastier and more tender. The shell plates from the chitons have been frequently found in the middens of First Nations. Middens are culturally-significant locations where shells, bones, utensils, and other artifacts and remnants were placed by indigenous peoples at a site that they occupied. Like a garbage pit, but all biodegradable. The Haida Nation, located along Northwest British Columbia and Southeast Alaska, call the gumboot chiton sgiidaa, which means “lying face-down forever.” The Samish Tribe of the central Salish Sea calls this chiton 7ókw’es, which you can hear by clicking on the link in the word.