Synthesis and degradation of juvenile hormone III during the final two larval stages of female and male crickets, Gryllus bimaculatus de Geer (Ensifera, Gryllidae)

Abstract

The rates of synthesis of juvenile hormone III were determined in female and male penultimate and final larval instars of the Mediterranean field cricket, Gryllus bimaculatus, using an in vitro radiochemical assay. Throughout the penultimate larval stadium, mean rate of juvenile hormone synthesis declines from about 4 pmol · hr−1 - pair corpora allata (CA)−1 on day 0 to less than 1 pmol · hr−1 · pair CA−1 on day 5, but increases again prior to the next larval moult (day 6). During the first 24 hr of the final larval stadium, mean rates of juvenile hormone synthesis are between 5–6 pmol · hr−1 · pair CA−1 and thereafter drop below 0.5 pmol · hr−1 · pair CA−1 by day 4. Immediately following imaginal ecdysis, the corpora allata of virgin females synthesize juvenile hormone III at higher rates than those observed throughout the final larval instar. The accumulation of methyl farnesoate within the corpora allata parallels the rates of juvenile hormone III synthesis, but at a lower level. Juvenile hormone III esterase activity in hemolymph, as measured in vitro, is moderate during the penultimate larval stadium (ca. 200 pmol · hr−1 · μl−1) and increases significantly to a high level from day 2 to the end of the final larval stadium. There is no sexual dimorphism in timing or magnitude of juvenile hormone III synthesis and juvenile hormone III esterase activity, respectively.