Effects of all‐trans retinoic acid on regenerating limbs of the fiddler crab,Uca pugilator

Regeneration of walking legs in the fiddler crabUca pugilatorrepresents true epimorphic growth since it involves organization of an undifferentiated blastema prior to regrowth of a new limb. Normal regeneration inUcaconsists of two major stages—basal growth and proecdysial growth. One of the earliest events in the basal growth stage of regeneration is the secretion of cuticle by epidermal cells that migrate under the scab at the site of limb loss. When crabs are maintained in a 0.05 mM emulsion of retinoic acid (RA) in sea water during the first 2 weeks following autotomy, the pattern of cuticle secretion is disrupted in many limb buds. Limb buds on RA‐treated crabs grow more slowly and are frequently malformed.