Rock Louse (Ligia pallasii)

Rock Louse (photo credit: Biodiversity of the Central Coast)

Description: The rock louse (also known as sea slater or northern sea roach) is a small flat isopod about 3.5 cm in length and 1 cm wide. Like other isopods, their body is segmented, they have two antenna, and a tail. They are often a mottled dark brown or gray and camouflage with the rocks that they live on.

Habitat: Rock louse can be found as far North as the Aleutian Islands of Alaska and as far South as Santa Cruz, California. They prefer to find shelter on rocks in the high intertidal zone. At Haystack Rock, the best place to look for rock louse is in rock crevices, especially above the mussel wall in the barnacle line/splash zone.

Diet: Scavenging for decaying plant and animal matter, rock louse help keep the high intertidal zone clean.

Tide Pool Tidbits:

  •  Rock louse are a member of the “ancestral” or short tailed group of isopods.

  • These isopods only life 1.5-2 years and often breed in the spring or early summer.

References: Walla Walla University