Ecdysteroids and regeneration in the fiddler crab Uca pugilator

Regeneration of lost walking legs in the fiddler crab Uca pugilator is divided into three distinct phases—wound healing, basal growth, and proecdysial growth. By means of HPLC/RIA analysis of levels and composition of endogenous ecdysteroid hormones and in vitro assays of 14C‐leucine incorporation, we have determined that the transition between anecdysis and proecdysis is the point at which limb bud growth is most affected by ecdysteroids. The growth that occurs during proecdysis is programmed during the anecdysis/proecdysis transition by a small peak of ecdysteroids (Peak I). Early exposure to 20‐hydroxyecdysone at this critical window is necessary for further proecdysial growth of limb buds. The later peak of ecdysteroids (Peak II) seen in the hemolymph of these crabs during late proecdysis does not seem to be involved in the regeneration process.