Journal of Insect Physiology 46 (2000) 969–976 www.elsevier.com/locate/jinsphys Regulation of vitellogenesis in the fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) Dorian Sorge a,b , Ralf Nauen a,* , Sebastian Range b , Klaus H. Hoffmann b a Bayer AG, Agrochemicals Division, Research Insecticides, D-51368 Leverkusen, Germany b Animal Ecology I, University of Bayreuth, D-95440 Bayreuth, Germany Received 8 June 1999; accepted 5 October 1999 Abstract Studies were undertaken to investigate vitellogenesis and its regulation in female adults of the fall armyworm, Spodoptera frugip- erda. A single female-specific protein, likely to be the S. frugiperda vitellogenin (Vg), appeared approximately 5 h after adult eclosion in the hemolymph of virgin females. The concentration of the protein increased with age as sodium dodecyl sulfate– polyacrylamide gel electrophoresis (SDS–PAGE) revealed. A protein with the same relative molecular mass was also present in egg extracts, but absent from hemolymph samples from male moths. The relative molecular mass of the designated S. frugiperda Vg was determined as 164.5±2.5 kDa. Vitellogenic oocytes became visible 36–48 h after emergence and egg deposition began on day 3 of adult life. Vg could not be detected in the hemolymph of females decapitated directly after eclosion. When decapitated virgin females were injected with the JH-mimic methoprene (MP), the level of Vg was comparable to that in non-decapitated moths, indicating that vitellogenesis in S. frugiperda depends on juvenile hormone (JH). However, the number of vitellogenic oocytes was somewhat lower than in non-decapitated virgin females. Injection of 20-hydroxyecdysone (20E) promoted Vg production to a similar extent in decapitated female moths, but in contrast to methoprene injection, treatment with 20E never resulted in the production of vitellogenic oocytes. In vitro cultivated ovaries of adult females dissected directly after eclosion produced lower amounts of ecdysteroids than those isolated on day 1 after emergence. Our results suggest a crucial role for 20E in the induction of vitellogenesis in the noctuid S. frugiperda, while JH seems to be essential for the continued uptake of Vg by developing oocytes and may trigger 20E biosynthesis in the ovary.  2000 Elsevier Science Ltd. All rights reserved. Keywords: 20-Hydroxyecdysone; Juvenile hormone; Methoprene; Oocytes; Vitellogenesis 1. Introduction Insect reproduction, and vitellogenesis and oogenesis in particular, are regulated by hormones such as juvenile hormone (JH), ecdysteroids and peptide hormones released by neurosecretory cells (Nijhout, 1994; Belle ´s, 1998). During vitellogenesis, female-specific proteins, the vitellogenins (Vg), are synthesized in the fat bodies of most insects, released into the hemolymph, trans- ported by carrier proteins to the ovarioles, and incorpor- ated into oocytes to provide a nutrient reserve for the developing embryo. The different reproductive charac- teristics so far studied in lepidopterans distinguish * Corresponding author. Tel.: + 49-2173-384441; fax: + 49-2173- 384932. E-mail address: ralf.nauen.rn@bayer-ag.de (R. Nauen). 0022-1910/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII:S0022-1910(99)00207-3 broadly between species starting vitellogenesis after adult emergence, and those in which Vg production begins before adult emergence (Belle ´s, 1998). A classi- fication of lepidopteran species based on general repro- ductive characteristics refers to the reduction in their dependence on metamorphic events for triggering egg maturation, and allows a rough division into four groups (Ramaswamy et al., 1997). The first group consists of species which initiate and complete egg development during the larval or early pupal stages and also show a direct or indirect requirement for ecdysteroids for pro- ducing Vgs, e.g. Bombyx mori (Onishi, 1987), Antheraea yamamai (Furusawa et al., 1993) and Lymantria dispar (Davis et al., 1990; Hiremath and Jones, 1992; Fesce- myer et al., 1992). The second group includes pyralid species such as the Indianmeal moth, Plodia inter- punctella, in which vitellogenesis is triggered by decreasing ecdysteroid concentrations in the hemo-