Water relations in eggs of the lone star tick, Amblyomma americanum, with experimental work on the capacity for water vapor absorption.

ABSTRACT

This study shows that water stress is not countered in eggs of the lone star tick, Amblyomma americanum (L.), using water vapor, and suggests involvement of liquid water as a developmental cue. Eggs fail to maintain an equilibrium water content in subsaturated air, hence, gain not equal to loss, with net water losses occurring at relative humidities near saturation and these eggs exhibit a three-fold drop in viability, but not incubation period, as compared to eggs held in saturated air. Amblyomma americanum eggs are stenohydric and feature low 58% water content, slow water losses <1%/h, and an impermeable chorion wherein the Arrhenius activation energy, Ea = -66J/K, is suppressed. Thus, enhancement of water retention, not water vapor absorption, permits eggs to resist desiccation.