YU, X.-L.; CHANG, E.S.; MYKLES, D.L.: Characterization of limb autotomy factor-proecdysis, a polypeptide that inhibits molting in the land crab

Regeneration of lost appendages must be coordinated with various other physiological processes to ensure successful molting in decapod crustaceans. Autotomy of at least 5 walking legs induces precocious molting in the land crab, Gecarcinus lateralis. Lost appendages are regenerated during the premolt stage of the intermolt cycle. If a limb regenerate (limb bud) is autotomized before a critical period during premolt, growth of any remaining primary (1�) limb buds (LBs) stops to allow regeneration of a secondary (2�) LB. Secondary LBs contain a factor, termed limb autotomy factor-proecdysis (LAFpro), that blocks molting when injected into premolt animals. Premolt animals (regeneration index 13 to 17) were injected three times at 2-day intervals with water-soluble extracts of either 1� or 2� LBs (about 2 LB equivalents per injection). Secondary LB extracts inhibited the growth rate of 1� LBs about 85%, while 1� LB extract had no effect. LAFpro was stable when boiled for 15 min in deionized water, but was inactivated when boiled in 0.1 M acetic acid. The factor was also inactivated by incubation with Proteinase K. Limb bud autotomy reduced the ecdysteroid levels in the hemolymph of premolt animals. These data suggest that LAFpro is a molt-inhibiting hormone-like polypeptide that suppresses ecdysteroid synthesis and secretion by the Y-organs. Supported by NSF (IBN-9904528).