Two cases of morphological abnormalities in snow crab Chionoecetes opilio

Abstract

The snow crab Chionoecetes opilio is an important fishery species in Japan, and its morphological abnormality has been reported in many cases. This report represents morphological abnormalities of snow crab based on photographic records. One male individual had a large lateral projection on the propodus of the left second pereiopod. This lateral projection was trapezoidal in shape and had two dactyl-like spines at the top base. These two spines were different in morphology from the movable and fixed fingers of the cheliped and the dactylus of the pereiopod. The other male individual was missing about a half of the fixed finger of the left cheliped, instead having another fixed finger protruding diagonally from just below the missing part.