Effect of methoprene and 20-hydroxyecdysone on salivary gland development of the lone star tick, Amblyomma americanum (L.)

Abstract

Topically applied juvenile hormone III analogues 7-S-methoprene and 7-S-hydroprene (50 μg/tick) modestly stimulated attached virgin Amblyomma americanum females to feed and attain average body weights of 27.1 mg (178% of controls, just 4% of mated controls), however, tick salivary gland protein levels were stimulated 133%, into the range of mated, early-rapid feeding female ticks (> 100 mg body weight). Na K - ATPase activity was also increased to levels seen in salivary glands of mated, early-rapid feeding ticks (212% of controls) by methoprene. Electron microscopy of salivary glands from treated ticks revealed euchromatic nuclei, partially swollen alveolar lumina, proliferation of basolateral labyrinth and increased rough endoplasmic reticulum, morphological changes normally seen in later feeding stages of mated females, but not in virgins. Treatment of attached, feeding females with 100 μg 20-hydroxyecdysone/tick also stimulated virgins to gain additional weight (195%) and total salivary gland protein (144%), but not Na K - ATPase activity. Methoprene stimulated protein level was not potentiated by additional treatments with 20-hydroxyecdysone. Tick salivary glands are thus partially, but differentially activated by methoprene and 20-hydroxyecdysone treatment while pre-mating weight arrest (feeding) is released only slightly.