Wildlife of the Week!

©Alexa Desautels. A Gumboot Chiton is spotted in the shallow waters of the intertidal zone in Bamfield, British Columbia.

It’s time for Wildlife of the Week! This week’s species is often found under the waves or on tidal rocky outcroppings and shores. If you’ve seen this animal before, you might have mistaken it for a very strange rock. The Gumboot Chiton (Cryptochiton stelleri) is one that continues to astonish many with its oval, stone-looking appearance. The animal is a marine invertebrate that moves around its surroundings with one strong foot, which also helps it cling to rocks. To learn more about the Gumboot Chiton, follow along below! 

The Gumboot Chiton is certainly a peculiar looking creature at first glance; but it is an incredibly unique and well-adapted species. This chiton may reach a maximum size of 33 cm long- that’s longer than a standard ruler! Therefore, this impressive size has given it the place of the largest chiton species in the world. The mottled, rock-like surface on the topside of the chiton is typically a dull hue, similar to the color of red bricks. This piece of the animal is called the girdle. This top surface is often bumpy, lumpy and uneven, surrounding much of the body. The chiton’s girdle covers its 8 shell plates (that all chitons carry); therefore this identification clue is hidden.

The Gumboot Chiton is a marine species, its range extending from Alaska to southern California and west to Japan. The species appears to favor colder regions (further north) above southern latitudes. It is found majorly within Kelp forest habitats, other rocky intertidal and subtidal zones, surge zones and tidal pools. Its maximum depth range is recorded to 65 feet. The animal may dwell on rocky or muddy surfaces, and blends in well with its surroundings. In many circumstances, the chiton appears still and “stuck” to rocks and other substrates. The chiton is able to move using a strong muscular foot, and it is said that this species is more easily swept away or detached from its surface from waves and other factors, due to its weaker grip. It is important not to attempt to dislodge or disturb a chiton or other marine species if you encounter them. 

The Gumboot Chiton is a herbivore, consuming varieties of algae. Most commonly, red algae is chosen, however young kelp, sea lettuce and giant kelp is also fed upon. Interestingly enough, this chiton feeds nocturnally (at night), but has been seen to feed during the day with select conditions (i.e. tidal pools in daytime fog). The feeding apparatus of all chitons is exceptional; they employ a tongue-like extension (radula), covered in strong magnetite teeth to manipulate and consume their food. 

Reproduction events for this chiton generally occur in the spring or summer months (varies by geography). Females and males spawn genetic material into the water (females release eggs first). After fertilization, trochophores begin hatching into plankton which then transition into larvae. Larvae settle and begin growing into adult chitons. Large gatherings on/ near shorelines may be attributed to spawning events. As adults, movement distances vary, but may be between 7 metres/day to 20 metres/year, depending on habitat. 

The Gumboot Chiton holds an impressive lifespan, with maximums ranging from 20-25 years old. Though the Gumboot Chiton is not prey to many, Sea stars, Tidepool Sculpin, Sea otters and the Lurid Rock Snail feed on the creature. This chiton has even been spotted forming a relationship with some polychaete worms and pea crabs.

As mentioned, the chiton has 8 shell plates underneath its girdle, and is able to repair these plates upon breakage! The Gumboot Chiton was traditionally and is still currently harvested as a food source by some Indigenous peoples within its range. Truly a fascinating marvel of ecology, the chiton group deserves significant attention for its remarkable lifestyle that has permitted its survival for over 500 million years. 

This species faces major threats due to believed diseases as well as human activities, namely the actions of global warming, sewage discharge, mining, oil and gas development and trampling, among others. Frequency of individuals and size structures have seen declines and changes in some areas. It is important to consider how long-lived, integral ecosystem species deal with the changing impacts of our world in order to best mitigate our own practices for global ecosystems. 

To try out some chiton trivia, follow along below! 

  1. True or False? The Gumboot Chiton has been recorded to breathe air. (ANS: True. Provided its gills are still wet, the chiton can breathe oxygen when out of the water). 
  2. There are ____ species of chitons around the world. (ANS: 650). 
  3. True or False? The Gumboot needs little food to survive (ANS: True). 

BONUS CHALLENGE:

What shape are each of the 8 shell plates? 

“Butterfly-shaped”. 

Article Authored By: Alexa D., B.Sc./ Five Star Whale Watching. 
To discover more about this creature, check out our References below!

Alaska Department of Fish and Game.

Alaska SeaLife Centre.

Monterey Bay Aquarium.