As part of my dissertation research (ages ago!), I reared Hommarus
americanus in the lab from stage 1 larvae to juveniles (~7 cm total length).
I noticed that all of these lab-reared lobsters had two cutter claws. At the
time, I asked around among my colleagues for the reason. It turns out that
the cutter claw is the default condition and that a crusher claw will
develop only if the young lobster manipulates hard objects, such as mollusk
shells, etc., during a narrow time frame during early juvenile development.
(I was feeding them a formulated pelleted feed.) Thus, claw asymmetry is not
genetically determined.

See articles by Govind and Pearce including:
Govind, C.K. and J. Pearce. 1989. Critical period for determining claw
asymmetry in developing lobsters. J. Exp. Zoo. 249: 31-35.

More recent:
Goldstein, J.S. and M.F. Tlusty. 2003. Substrate determinants and
developmental rate of claw asymmetry in American lobsters, Homarus
americanus. J. Crusta. Biol. 23: 890-896.


Patricia M. Biesiot, Ph.D.
The University of Southern Mississippi
Department of Biological Sciences
118 College Dr., #5018
Hattiesburg, MS 39406-0001