Effect of 20-hydroxyecdysone and haemolymph on oogenesis in the ixodid tick Amblyomma hebraeum

Neuropeptide signaling sequences identified by pyrosequencing of the American dog tick synganglion transcriptome during blood feeding and reproduction

“…Deposition of vitellogenin into the oocytes via the vitellogenin receptor results in vitellin formation and subsequent oviposition . Seixas et al (2008) demonstrated that in Amblyomma hebraeum 20-E triggers Vg expression but not deposition into the oocytes suggesting that a "vitellogenin factor" in the hemolymph is required. Regardless, in both species blood feeding initiates the cascade of events that likely results in the release of a hormone with a similar function to PTTH from the synganglion that triggers 20-E synthesis by the epidermis although this hormone has not been identified.…”

“…However, only recently have the major yolk proteins been fully sequenced, and only a few species have been studied Mitchell et al, 2007). Furthermore, other recent studies on vitellogenesis in ticks indicate that a consensus model of tick reproduction will require studies from multiple taxa in order to understand key regulatory differences (Seixas et al, 2008).…”

Molecular characterization of two vitellogenin genes from the tick, Amblyomma hebraeum (Acari: Ixodidae)

“…There were no significant differences in ovipositional delay, egg masses produced, or hatching success between females injected with AhVg-dsRNA constructs versus ␤-lactamase-dsRNA or TE controls. Ovaries harvested from females injected with any of the AhVg-dsRNA treatments did not weigh significantly less than he controls, as a percentage of engorged body weight, nor was there any significant difference in ovarian growth phase (OGP), as defined by Seixas et al (2008). However, average oocyte lengths of AhVg1-dsRNA-(518 ± 15 m) and AhVg1 + 2-dsRNA-injected females (487 ± 22 m) were slightly smaller than that of the combined controls (561 ± 5.2 m; p = 0.015 and p < 0.000 respectively).…”

“…At 8 days post-engorgement, females were dissected, and tissues harvested. The ovaries were weighed, their developmental stage assessed (Seixas et al, 2008), and the eight largest oocyte lengths recorded for each ovary. Total RNA was extracted from the fat body of each female and cDNA synthesized to examine dsRNA mediated knockdown.…”

“…JH has not been authenticated in ticks (Neese et al, 2000;Coons, 2013). Vitellogenesis in ticks is induced by a blood meal and regulated by ecdysteroids Kaufman, 2002, 2004;Thompson et al, 2005;Seixas et al, 2008).…”