Limb developmental stages of the newt Notophthalmus viridescens.

The current study consists of a detailed description of normal larval forelimb and hindlimb development in the newt, Notophthalmus viridescens. This is the first comprehensive record of staging limb development in this urodele amphibian species, augmenting Fankhauser's work which was published in fragments 60 years ago. Larvae were obtained by natural spawning, without hormone injections and while experimental conditions such as temperature and light cycles were kept constant (20 degrees C and 12L/12D), larval sizes have been added here merely as guidelines as development is influenced by a number of extrinsic factors. Care has been taken to indicate similarities to either the Harrison or Glucksohn stages, although this relates mainly to their morphological descriptions of the limbs. Observations from limb use are also mentioned in the text where pertinent to the description of development.