Methyl farnesoate controls adult male morphogenesis in the crayfish, Procambarus clarkii

In the control animals, 4 out of 4 untreated Form I males molted into Form II, while 6 out of 7 Form IIs molted into Form Is. Eight of 8 ablated Form Is molted into Form IIs as expected, while 5 of 5 ablated Form IIs molted into Form IIs, instead of Form Is. MF treatment of intact animals resulted in 6 of 7 Form Is becoming Form IIs and 5 of 6 Form IIs becoming Form IIs. These results were highly significant in comparison of Form I and IIs in each treatment (eyestalk intact, eyestalk ablated and eyestalk intact with MF) by a chi square analysis, P=0.006, P<0.0005, and P=0.013, respectively. MF premolt blood levels suggested that Form IIs were produced in the presence of 1.3 ng/ml MF, while Form Is result from MF levels less than 0.5 ng/ml. Since both eyestalk ablation and MF treatment resulted in the failure of Form IIs becoming Form Is, it was concluded that the control of morphogenesis of primary reproductives (Form Is) depends on a low level of MF prior to the molt, while Form IIs are formed in the presence of increased levels of MF.