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Hormonal control of diapause in the tick Argas arboreus

1976; Elsevier BV; Volume: 22; Issue: 12 Linguagem: Inglês

10.1016/0022-1910(76)90059-7

1879-1611

Galila M. Khalil, Nawal Shanbaky,

Vector-borne infectious diseases

During the mid-diapause period of the female tick Argas arboreus, nerve ganglion (G) extract (GE) from nondiapause (ND) females injected into diapause (D) female haemocoel after feeding, but not before feeding, terminated diapause in 50% of the ticks. ND haemolymph (H) failed to terminate diapause. Reciprocal injections of D GE, and H induced diapause in most ND females. During the late diapause season, ND GE, and H terminated diapause in D females and reciprocal injections of D GE, and H failed to induce diapause in ND females. The results suggest that in A. arboreus the facultative diapause results from gonadotropic hormone (GTH) deficiency in the presence of a diapause inducing factor (DIF). We suggest that the DIF is formed under the influence of short photoperiod in unfed females. The DIF interferes with normal release of the GTH formed in ganglion after feeding and also with the effect of GTH in the H by direct inhibition and/or by preventing the target organs (ovary and/or gut cells) from responding to GTH. The DIF is degraded slowly during short photoperiod and rapidly during long photoperiod.