Hormonal Control of the Molt Cycle in the Fiddler Crab Uca pugilator

Comparison of the circulating steroids in the blood of crabslacking neurosecretory eyestalk centers and crabs with thosecenters intact (but lacking several walking legs) has revealeddifferences in vivo that can be attributed to eyestalk factors.It is concluded that eyestalk factors (including the putativemolt-inhibiting hormone, MIH): 1) exert control in vivo overproduction of 25-deoxyecdysone by the crab Y-organ, 2) controlcyclic steroid production throughout anecdysis and parts ofproecdysis and 3) are not solely responsible for the increasedsteroid production that occurs during late proecdysis. Usingthe data presented here and previously published data, a simplefeedback model for the control of Y-organ activity is proposed.The model suggests that the Y-organs of the crabUca pugilatorare modestly active during anecdysis but become further activatedduring late proecdysis. The increased activation requires morethan eyestalk removal and may involve additional extra-eyestalkfactors.