LAUFER, HANS*; DEMIR, NESLIHAN; AHL, JONNA/S.B.; University of C onnecticut, Storrs; University of Connecticut, Storrs; Eli Lilly, Indianapolis: Male Morphotypes of the Crayfish Procambarus clarkii are Controlled by Methyl Farnesoate

Adult male crayfish exist in two morphotypes. Primary reproductives (Form I) have large spiny chelae and spines on the ischiopodites of the third and fourth pairs of walking legs. Non-reproductive Form II males have smaller chelae and no spines on the ischiopodites (J. Huner, 1994). Form II can molt into Form I, and Form I can molt into Form II in nature. We investigated the hormonal control of these transitions in two ways, by eyestalk ablation, and by methyl farnesoate (MF) treatment. Eyestalk ablation accelerates molting and increases MF in the blood. MF is a hormone regulating both reproduction and morphogenesis (Laufer et al., 1987). MF was quantitated by HPLC. Four out of 4 untreated Form I males molted into Form II, while 6 of 7 Form IIs molted into Form Is. One Form II underwent a stationary molt. Eight of 8 ablated Form Is molted into Form IIs as expected, while 5 of 5 ablated Form IIs molted into Form IIs. MF treatment (2ug/animal/day) of intact animals resulted in 6 of 7 Form Is becoming Form IIs and 5 of 6 Form IIs became Form IIs. These results are highly significant by chi square analysis ( P < 0.01). MF premolt blood levels suggested that Form IIs are produced in the presence of 1.3ng/ml MF, while Form Is result from MF levels of 0.5ng/ml. Since both eyestalk ablation and MF treatment result in the failure of Form IIs becoming Form Is we conclude 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 elevated levels of MF.(Supported by the Sea Grant College Program)