Evergreen Natural History Database

Common name(s): Oregon pill bug

Size:
~1cm in length.

Range:
The order Isopoda is found worldwide.

Habitat:
Under rocks in the intertidal zone. Commonly found under the bark of rotting debris.

Misidentification:
Most commonly misidentified as Gnorimosphaeroma insulare or Gnorimosphaeroma noblei. In Gnorimosphaeroma insulare the third pleonite is crowded out and this species is found in brackish to fresh water. The other species, Gnorimoshpaeroma noblei, has the basal articles of antennae 1 touching each other at the midline (no rostrum).

Life History:
These invertebrates are brooders. The embryos are held in the brood pouch of the female (marsupium) until they are released as juveniles (manca) which are not fully developed. The manca lack the last pair of peropods and therefor dispersal relies on their ability to crawl. The adult form can swim, only they swim upside-down. Being scavengers and browsers they are commonly found feeding on living and rotting algae and fish.

Natural History:
These Isopoda have a compact body with tough exoskeleton. When threatened these animals protect their legs and soft undersides by rolling up into a ball. This Isopod is identified by having the segments of the abdomen (pleon) fused together to form only two sections. The last section (pleotelson) has flat uropods on the side.

Predators:
Other Isopoda, fish, and many invertebrates.

Links:

Information on Isopoda.

Fresh Water Isopoda.

Suggested Readings:

Brown, Vinson and Rovetta, Ane (1996). Exploring Pacific Coast Tidepools. Naturegraph Publishers, Inc, Happy Camp, 127 pages.

Hatch, M. H. (1947). The Chelifera and Isopoda of Washington and Adjacent Regions. University of Washington Press, Seattle, 274 pages.

Kozloff, Eugene N. (1999). Marine Invertebrates of the Pacific Northwest. University of Washington Press, Seattle, 539 pages.

Last updated Friday, August 25, 2006, by Lisa Ferrier