Virginia Institute of Marine Science
Throughout history mankind has probably reacted to all natural phenomena by some degree of either attraction or repulsion. Certainly the same objects or phenomena are not viewed exactly alike by all. The rhythmic, as contrasted with discordant, motion, or symmetrical versus non-symmetrical patterns of structure may elicit various feelings in different people. Since natural growth generally produces structural patterns which follow some type of symmetry, this is what we usually expect. While sluggish motion and radial symmetry often are associated, usually animals which dart about or are quick in action have evolved along lines of bilateral symmetry, as have fishes and crabs. Any deviation from recognized actions and structural patterns is certain to attract one's attention . In contrast to a fish and other bilaterally symmetrical animals, including most crustaceans, the crab darts sideways, not along its axis of symmetry. In this study we have been attracted to deviations from symmetry in the external structure of crab claws.
Shuster, Carl N.; Ulmer, David H.B. Jr.; and Van Engel, Willard A., A commentary on claw deformities in the blue crab (1963). Estuarine Bulletin, 7(2-3), 15-23.