Hemolymph juvenile hormone titers in pupal and adult stages of southwestern corn borer [ Diatraea grandiosella (pyralidae)] and relationship with egg development

Abstract

Juvenile hormones I, II and III were monitored in hemolymph of pupal and adult stages of various ages of Diatraea grandiosella females. JH III was the predominant homologue followed by JH II, and JH I was rarely detectable. At day 5 after pupation, no JH was detectable. JH titers increased from 7.5 days after pupation to a peak of 24.8 ng ml −1 JH II and 26 ng ml −1 JH III at adult emergence and then declined to low levels by 24 h after emergence. Ovarian development in D. grandiosella parallels changes in hemolymph JH titers, but the role of JH in vitellogenesis is unclear since the time of vitellogenesis initiation has yet to be determined. No apparent vitellogenin deposition was observed in eggs 5 days after pupation. Some oocytes were partially vitellogenic by 7.5 days after pupation and oocytes continued to grow afterwards, but no oocytes were chorionated during the pupal stage. Chorionated oocytes were observed in 24-h-old female moths. Juvenile hormone is essential for chorion formation in this species, because decapitated pupae treated with 10 μg JH III in corn oil developed chorionated oocytes while decapitated pupae treated with corn oil did not.