The activity and stability of injected juvenile hormones (JH I, JH II, and JH III) in last-instar larvae and adult females of the cockroach Nauphoeta cinerea

Abstract

The relative activities of the three known juvenile hormones (JHs) injected in olive oil are investigated in a larva test, a vitellogenin test, and an ovary growth test. The degree and character of juvenilization obtained after injection of JHs is dependent on the developmental stage at the time of injection, on the dose, and on the kind of JH used. In all developmental stages investigated JH I and JH II have similar and up to 10-fold higher juvenilizing activity than JH III. Measurement of the exogenous JH I and JH III titers at different developmental stages reveals that until at least 2–3 days after injection, the titer of JH III in hemolymph is higher than that of JH I and that only 1% or less of the injected JH circulates in hemolymph. This indicates that the difference in juvenilizing activity between JH I and JH III cannot be due to different elimination rates and suggests that JH I and JH III have different modes of action in larval Nauphoeta. For the vitellogenin and the ovary growth test decapitated adult females are used. Injection of small doses of each JH induces the synthesis of vitellogenin while high doses of each JH have to be injected to stimulate oocyte growth. Thus in adult females the three JHs have similar relative activities.