Pareurythoe californica is a species of bristle worm found in the rocky intertidal of the Eastern Pacific, particularly in California.
Pareurythoe californica has a long and gradually tapered body that is flat dorsally and square in its cross-section. As members of the family Amphinomidae, P. californica bears distinctive chaetae (bristles) that project laterally from its body. These give the organism a hairy appearance, and inspire common names like bristle worm and sea mouse. The chaetae are used as a defense mechanism and a deterrent to predators, and they can induce irritation in humans when touched.
P. californica are gonochoric. Eggs are produced in the worm's nephridium, and after they are fertilized, they develop into planktonic larvae, which metamorphose into a juvenile stage before reaching the adult stage.
P. californica can be described as both a predator and a scavenger. It feeds on a variety of organic materials, including detritus, algae, and occasionally small invertebrates. Additionally, it can obtain nutrients by absorbing amino acids from seawater.