AbstractHeptacarpus pictus (Stimpson, 1871) has been thought to be distinct from H. sitchensis (Brandt, 1851) based on the epipods: the former having epipods on the third maxillipcds and first and second pereopods, the latter having epipods on the third maxillipeds and first pereopods but not the second pereopods. The relative lengths of the antennular and antennal peduncles and the third maxillipeds to each other have been mentioned to be different in the two species. However, the description by Stimpson states that epipods of H. pictus were present on the first pereopods, not the second; the existing syntype of the species does not have epipods on the second pereopods. Study of over 280 specimens from British Columbia, Canada; California, U.S.A. and Baja California, Mexico, shows that individuals with epipods on the third maxillipeds and first pereopods occur throughout the range and that specimens also with epipods on the second pereopods occur in Monterey Bay and south of Point Conception, California. One individual was found with epipods on the third maxillipeds and first pereopods on both sides and an epipod on the second pereopod on the right side only. No other consistent differences in habitat, color or morphology were found between the specimens. We conclude that H. pictus is a junior synonym of H. sitchensis, and that shrimp with epipods on the second pereopods as well as the third maxillipeds and first pereopods constitute a morph of H. sitchensis.
