Excirolana kincaidi (Hatch, 1947)

Common name(s): Sand beach isopod, Sandy beach isopod

Phylum Arthropoda
Subphylum Crustacea
Class Malacostraca
Subclass Eumalacostraca
Superorder Peracarida
Family Cirolanidae
Excirolana kincaidi, 8 mm long, from Shi Shi beach sand
(Photo by: Dave Cowles, Sept 2007)
Description:   As with all Flabelliferan isopods, the uropods are lateral to the pleotelson (photo), the uropodexopodites do not arch over the pleotelson (photo), pereopod 1 is not greatly enlarged and is not subchelate (photo), and the animal is less than 7 times as long as wide. Excirolana kincaidi has 5 visible pleonites plus the pleotelson.   Both the endopod and the exopod of the uropods are well developed and lamellar.  The animal cannot roll into a ball and does not bore in wood.  None of the pereopods have large, hooklike dactyls for attaching to fishes, though some do have small hooks (photo).  The posterior border of the telson is fringed with long, plumose setae (photo).  The telson is angular and comes to a fairly sharp point at the end (angle of point about 120 degrees).  The animal has a spatulaterostrum (this and the long plumose setae on the telson distinguish genus Excirolana from genus Cirolana).  The eyes are lateral on the head and the distance between them is greater than their diameter.

How to Distinguish from Similar Species: Excirolana vancouverensis has a rounded tip on its angular telsonExcirolana linguifrons has a broadly rounded or truncate tip to the telson and reaches only 4 mm in length.

Geographical Range:  British Columbia to Half Moon Bay, CA

Depth Range:  Intertidal

Habitat:  Sandy beaches.

Biology/Natural History:  These isopods alternately bury themselves in the sand and actively forage for dead animal matter.  They seem to be especially active in the shallow swash of retreating waves on sandy beaches.  Large numbers may quickly congregate around an animal carcass that washes in on a sandy beach while it is still in the water, and quickly strip the carcass of flesh.  This is the most common Excirolana species along the Washington coast.  Predators include sanderlings.

Note:  Very few crustaceans will actually bite you but this nasty little creature is definitely one of them.  Barefoot waders in an area with Excirolana will find that the animals quickly swim toward and swarm over bare feet, biting them so hard that blood will be flowing within moments.  Since the animals are so small the bites are tiny but painful like a pin prick, and the animals are often present in swarms of thousands.  Rapidly shuffling the feet reduces but does not eliminate the number of bites.



Dichotomous Keys:
  Kozloff 1987, 1996
  Smith and Carlton, 1975

General References:
   Kozloff, 1993
   Morris et al., 1980
   Niesen, 1997

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

I have seen (and felt!) this species on sandy beaches of the outer coast, such as Kalaloch beaches, 2nd and 3rd beach, and Shi Shi beach.

Ventral view
This ventral view shows that both sets of antennae are well developed.  Some of the pereopods have small hooks on the end.  The mandibles are dark and hardened--the better to bite you with!

Head ventral

This closeup ventral view of the head shows the hardened, biting jaws (mandibles) and the first several pereopods.  The maxillae and the maxillipeds are light colored and lie between the mandibles and the first pereopods, which have small dark hooklike dactyls.  The first pereopod is has a simple dactyl and is neither chelate nor subchelate.  Notice that the eyes are lateral and can easily be seen from the ventral side.  The spatulate rostrum can be seen protruding between the antennae.

Telson dorsal
This dorsal view of the telson shows the angular but rounded tip and the long plumose setae on the end.  The outlines of the uropods, which are ventral and lateral to the telson, can be seen through the telson.

Notice that both rami of the uropods have flattened plates.  Some of the terminal setae from the uropods are projecting beyond the telson.

Telson ventral
This ventral view of the telson shows the uropods, which are folded in under the telson in this view but can extend out to the sides to form a tailfan.

Authors and Editors of Page:
Dave Cowles (2007):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)