The gumboot chiton, Cryptochiton stelleri, also known as the Giant Western Firey Chiton, is the largest of the chitons, growing to 36 cm (14 in) and over 2 kg (4.4 lb). It is found along the shores of the northern Pacific Ocean from Central California to Alaska, across the Aleutian Islands to the Kamchatka Peninsula and south to Japan. It inhabits the lower intertidal and subtidal zones of rocky coastlines.
Chitons are molluscs which have eight armored plates (called valves) running in a flexible line down their back. Unlike most chitons, the gumboot's valves are completely hidden by its leathery upper skin or girdle, which is usually reddish-brown, brown, and occasionally orange in color. The gumboot chiton's appearance has led some tidepoolers to fondly refer to it as the "wandering meatloaf."
The name "Gumboot Chiton" seems to derive from a resemblance to part of a rubber Wellington boot or "gum rubber" boot
The Latin name Cryptochiton stelleri means Steller's hidden chiton. "Steller" is in honor of the 18th-century German zoologistGeorg Wilhelm Steller, who first described many species of the northern Pacific seashore. "Hidden" or "concealed" refers to the fact that the eight shelly plates characteristic of chitons are not visible, being totally internal in this genus of chiton. Many taxonomic names for chitons are based on the appearance of their plates or valves, and so it is most likely that the "hidden" portion of the name refers to the valves being completely obscured by the gumboot's girdle.
The gumboot chiton's underside is orange or yellow and consists mostly of a large foot similar to that of other molluscs like snails or slugs, with gills found in grooves running along the outer edge of the foot. The gumboot chiton is found clinging to rocks, moving slowly in search of its diet of algae, scraped off of rocks with its rasp-like retractable radula, covered with rows of magnetite-tipped teeth. It also eats other marine vegetation such as sea lettuce and giant kelp. Anocturnal creature, the gumboot generally feeds at night and often remains in a hiding place during the day — although on foggy days it may be found exposed in tide pools or on rocks.
The gumboot can live for over 40 years. It has few natural predators, the most common being the lurid rocksnail,Ocenebra lurida — although the small snail's efforts to consume the chiton are generally limited to the outer mantle only. It is sometimes reported that the lurid rocksnail is in fact the gumboot chiton's only predator, but others list such animals as the sea star Pisaster ochraceus, some octopus species, and the Sea Otter.
Several other animal species have been observed living within the gumboot's gills; the relationship is thought to becommensal: neither harmful nor helpful to the chiton. One researcher found that more than a quarter of gumboots hosted an Arctonoe vittata, a pale yellow scale worm which can grow up to 10 cm (3.9 in) length. Opisthopus transversus, a small crab, is also sometimes found within the gills.