Parasite-altered behavior in a crustacean intermediate host: Field and laboratory studies

The effects of the acanthocephalan parasite Pomphorhynchus laevis on the be havior of its crustacean intermediate host, the amphipod Echinogammarus sta mmeri, were studied. A drift study revealed that infected amphipods were di sproportionately represented in drift samples taken throughout a 24-hr peri od; infection with more than 1 parasite enhanced this effect. Infection als o interacted with the daily timing of drift, with parasitized amphipods beg inning to drift earlier in the evening. Two distinct behaviors quantified i n laboratory settings may play a role in this increased drifting behavior: parasitized amphipods showed (1) an increased preference for an illuminated environment and (2) increased activity in comparison to nonparasitized con specifics. These results are consistent with previous studies on the effect s of P. laevis on another amphipod host, Gammarus pulex, and provide new da ta on the activity level of P. laevis-infected amphipods.