Juvenile hormone-like substances can induce vitellogenesis in the tick <i>Ortnithodoros moubata</i> (Acarina : Argasidae)

Topical application of different juvenile hormone analogs (JHA) or of a mixture of stereoisomers of insect juvenile hormone (JH) 1 and 3 to fed virgin female <i>Ornithodoros moubata</i> immediately after feeding induced vitellogenesis and egg-laying in up to 70 of treated females. In controls only 13.7 oviposited. The eggs were sterile, with abnormal shape, but their number versus the weight of engorged females was normal or sometimes greater than in mated females. However, preoviposition period was longer than in mated females. <br> It was more difficult to induce egg-laying by similar topical applications 100 days after feeding of virgin females. A maximum of 58 of ovipositing females was obtained with a very high dosage of JH mixture (500 μg). Injection of this mixture into the females was more potent; 15 to 50 μg induced oviposition in about 60 of the females. The preoviposition period was also longer than in control females. <br> Our results suggest the presence of a JH-like substance which is involved in the hormonal control of vitellogenesis. However, since natural isomers of JH were much less efficient than isomeric mixtures or JHA, we suppose that the natural tick hormone does not correspond to JH, but rather to a JH-like substance.