Kelp Isopod    Idotea wosnesenskii



These shrimp-like creatures crawling about on a barnacle-covered rock are members of a group of animals, called isopods, which are related to shrimp, crabs and amphipods .  Characterized by the numerous, similar appearing body segments and legs, they sport two large antennae on their heads. Body size (to 1.5 inches) dwarfs that of other isopods and their cousins the amphipods.  The body color ranges from pink through olive green to a dark brown depending on where the animal makes it's home.  Individuals on brown kelp tend to be brown while those on eel grass are green which is probably the result of selective predation on young individuals that don't match their background.  


They are also known as the rockweed isopod due to their frequent occurrence on this marine, high intertidal plant and also the pickle bug because of their long green shape reminds people of a small dill pickle.


The Kelp Isopod can be found clinging to marine plants and worm tubes under floats, crawling among beds of marine plants or hiding under intertidal and shallow subtidal rocks from Alaska to southern California.   When disturbed they swim using small paddles under their abdomen while holding their legs to the side of the body ready to grab on to a solid surface.


They mainly feed on marine plants but have also been found preying on the eggs of a marine snail.  They are fed upon by a variety of animals including other invertebrates, fish and birds.


Reproduction occurs in the spring when the male fertilizes the female who then holds the young in body pockets until they hatch as miniature adults.