Spontaneous generation of bilateral symmetry in the paired claws and closer muscles of adult snapping shrimps

Adult snapping shrimps Alpheus heterochelis (Say) have paired asymmetric claws consisting of a major or snapper claw and a minor or pincer claw. An unusual condition of bilateral symmetry consisting of paired snapper claws arose spontaneously in several snapping shrimps by transformation of the pincer to a snapper in the presence of an existing contralateral snapper claw. Transformation in the external morphology and fibre composition of the closer muscle was completed within two intermoult periods in the majority of cases where true symmetry was achieved and once established became permanent. Thus snapping shrimps, which are by nature solitary, when continually exposed to each other in the laboratory may transform their pincer to a snapper without any trauma to the existing snapper claw.