Snail's Odyssey: Crustacea-Isopods

Crustacea
Isopods

There are about 5000 world species of marine isopods, but less than 20 are common in intertidal and supratidal regions of the west coast of North America. Owing to their generally nocturnal habits and preference for under-rock and under-seaweed habitats, many species are not obvious to the casual observer. An equal or greater number of species are parasitic or wood-boring (with a few exceptions the parasitic species are not included in the ODYSSEY). Isopods are of special interest because terrestrial representatives frequent our gardens (woodlice and sowbugs), and transitional evolutionary forms exist from the more advanced terrestrial species to prototypal land colonisers living in the supratidal region of west-coast shores.

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

Isopods along with shrimps, crabs, barnacles, and amphipods (in the order of occurrence in the ODYSSEY) are classified in the Subphylum Crustacea of the Phylum Arthropoda:

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

Subphylum Crustacea (lit. “crust or rind” L.), referring to the hard calcified exoskeleton

Class Malacostraca includes all the “advanced” crustaceans

Order Isopoda (lit. “equal feet” G.), referring to 7 pairs of undifferentiated locomotory appendages; includes about a dozen recognised suborders, of which four are represented in the ODYSSEY

Suborder Flabellifera includes Limnoria, Cirolana, Exocirolana, Gnorimosphaeroma, Exosphaeroma

Suborder Valvifera includes Idotea

Suborder Epicaridea includes parasitic bopyrids

Suborder Oniscidea includes the semiterrestrial Ligia and many terrestrial species