Mollusca
Chitons
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Fig. 1.  Gumboot chiton Cryptochiton stelleri attached to a rock in the intertidal zone at Botanical Beach, British Columbia

Diversity and abundance of chitons¹ on the west coast of North America is among the highest in the world.  Some 40 species are present from the Aleutian Islands to Baja California. About 16 reasonably common intertidal and subtidal species of Mopalia²  are included, as is the largest species in the world, the gumboot³  chiton Cryptochiton stelleri. (Fig. 1).  In certain Caribbean islands where they once were harvested as food, chitons are sometimes referred to as “coat-of-mail” shells or “sea beef”.  The large muscle mass comprising the foot, however, is tough, rubbery, and flavourless.

NOTE¹  the word refers to the tunic worn by men in ancient Greece, a sort of thick wool, sleeveless, shirt

NOTE² a marvelous synopsis of the molecular phylogeny of the genus Mopalia in the North Pacific basin by Stanford University and California State University researchers can be found at Kelly & Eernisse 2008 Invert Systematics 22:17

NOTE³  presumably named after its resemblance to the sole of a Wellington boot or gumboot.  The word “gumboot” reminds us of the time when such wading boots were made out of natural, or gum, rubber instead of synthetics.  Cryptochiton stelleri reaches lengths greater than 30cm and live masses approaching 1kg

Kelly & Eernisse   2008   Invert Systematics 22:17

ANIMATION of the snail's odyssey © Thomas Carefoot 2026
map used by the snail in A SNAIL'S ODYSSEY

To navigate through the ODYSSEY:

  • Select a TOPIC from the menu at the top of the screen
  • OR: play the animation to the left
  • OR: follow the snail's ODYSSEY by CLICKING on any X-marked invertebrate on the map above

Phylum Mollusca (lit. “soft” L. or “shellfish” L.)

Class Polyplacophora (lit. “many plates” G.), referring to the 8 protective shell plates, including several dozen shallow-water inhabiting west-coast species

   

Research Study 1

Fig. 2.  A sampling of chiton species in the Salish Sea; photos taken in situ
Courtesy Roger Clark and The Festivus
Fig. 1.  Location of the Salish Sea
Courtesy Roger Clark and The Festivus

There are some 40 species of chitons inhabiting the west coast of North America from Alaska to California, making this area the richest in the world for diversity of this taxon.  From tiny species less than 0.8cm in length to giants of 35cm or more, the size range of these species would encompass most or all that of all world species.  Indeed, the entire size range of chitons in Great Britain and European waters is less than the radula length of an adult gumboot chiton Cryptochiton stelleri.  Two species of genus Placiphorella, unique for their ambush-carnivore feeding habits, are also represented.  A researcher at the Santa Barbara Museum of Natural History has published photos and descriptions of 40 species, most or all of which are found in the Salish Sea (Figs. 1 - 2). 

NOTE  the Salish Sea comprises inland waters of British Columbia, Washington, including Puget Sound, Strait of Georgia, and Strait of Juan de Fuca.  Its name derives from the Coast Salish Indigenous Nations who have dwelt in the area for many thousands of years

 

 

 

 

 

PHOTOS OF SPECIES OF WEST COAST CHITONS INHABITING SHALLOW COASTAL WATERS FROM ALASKA TO BAJA CALIFORNIA CAN BE FOUND IN 8 CHITON GALLERIES (access via above menu):

 

 

 

 

 

Quick guide to genera featured in CHITON GALLERIES:

                                CHITON GALLERY 1:  Lepidochiton, Hanleyella, Deshayessiella, Chaetopleura, Stenosemus, Lepidozona
                                                                 2:  Lepidozona
                                                                 3: Tripoplax, Cyanoplax, Mopalia
                                                                 4:  Mopalia
                                                                 5:  Mopalia 
                                                                 6:  Mopalia, Dendrochiton, Placiphorella
                                                                 7:  Tonicella
                                                                 8:  Cryptochiton, Katharina

 

Clark   2020   The Festivus 52 (4): 294