Nawal M. Shanbaky

The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 22. The effect of feeding on hormonal control of egg development in Argas (Persicargas) arboreus☆

The blood-meal is essential to complete ova development by supplying nutrients and by stimulating hormone production in mated female Argas (Persicargas) arboreus. Within 3 days after feeding, the hormone is synthesized in the nerve ganglion and afterward is released into the hemolymph. Isolating the ovaries by ligation from the nerve ganglion during the hormone synthesis period interfered with ova development. Injecting an extract of nerve ganglia from 3-day-fed, mated females and of hemolymph from 4-day-fed, mated females into mated, recently fed females induced the same degree of ova development in their isolated ovaries as in fed, mated control females. Injecting nerve ganglion extract from 3-day-fed, mated females into mated, unfed females did not induce ova development.

Hormonal control of diapause in the tick Argas arboreus

Abstract 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.

The subgenus persicargas (Ixodoidea: Argasidae: Argas). 25. Effect of temperature on diapause termination in female A. (P.) arboreus Kaiser, Hoogstraal and Kohls.

Abstract The effect of constant 26, 30, 34, and 37 C temperatures on diapause incidence (percentage of diapause females) and intensity (duration of preoviposition period) was compared in field-collected (FC) and laboratory-reared (LR) F 1 and F 2 female A. (P.) arboreus . Diapause incidence, 89–100%, and intensity 115–133 days, in the FC were high at all temperatures except at 30 C when the intensity was reduced (84 days). Diapause incidence, 91–94%, and intensity, 132–137 days, in LRF 1 were high at 26 and 30 C. At 34 and 37 C, both (33% and 78 days) were lower than in FC and LRF 1 at 26 and 30 C. Diapause incidence was always lower in LRF 2 than in FC and LRF 1 and decreased as the temperature increased (58, 30, 17, and 0%, respectively). Diapause intensity in LRF 2 at 26 C (133 days) was high and similar to that in FC and LRF 1 at 26 C but was low at 30 and 34 C (84 and 87 days, respectively). In all groups, diapause intensity was higher in females kept outdoors (191–218 days) than in those held in the laboratory. The results suggest that rearing in the laboratory caused an increased sensitivity of diapause LRF 1 and F 2 females to high temperature.

The subgenus Persicargas (Ixodoidea: Argasidae: Argas). 33. Effect of gamma radiation on first nymphal instar A. (P) arboreus and adult fertility.

Gamma radiation doses higher than 1,000 rads are lethal to first nymphal instarArgas (Persicargas) arboreus. Only 50% of first nymphal instars receiving 1,000 rads reach adulthood but those receiving 100–500 rads survive normally. Males resulting from irradiated first nymphal instars are almost normally fertile. Female germinal cells tolerate higher radiation doses received in the first nymphal instar stage than in the adult stage. Females resulting from first nymphal instars receiving doses higher than 100 rads are less fertile (egg number and percent hatch) than normal and produce F1 larvae of lower than normal viability. Progenies of females irradiated as nymphs apparently inherit lethal genes, which may be useful, if irradiated at critical stages, in tick control.