Juvenile hormone and methyl farnesoate production in cockroach embryos in relation to dorsal closure and the reproductive modes of different species of cockroaches

Abstract

Juvenile hormone (JH), produced by the corpora allata (CA), is first detectable after dorsal closure, a conspicuous event in embryogenesis. The present research found that the timing of dorsal closure was consistently at about 45% of the total embryonic development time across most of the oviparous and ovoviviparous cockroach species examined. These included the ovoviviparous cockroaches Blaberus discoidalis, Byrsotria fumigata, Rhyparobia maderae, Nauphoeta cinerea, Phoetalia pallida, Schultesia lampyridiformis, and Panchlora nivea, as well as the oviparous cockroaches Blatta orientalis, Periplaneta americana, Eurycotis floridana, and Supella longipalpa. However, the only known viviparous cockroach Diploptera punctata completed dorsal closure at 20.8% of embryo development time. Methyl farnesoate (MF), the immediate precursor of JH III, is considered a functional molecule in crustaceans; however, in insects its function is still unclear. To understand the role of JH and MF in cockroach embryos, I compared JH and MF biosynthesis and release in several cockroach species of known phylogenetic relationships. Using a radiochemical assay, the present research showed that cockroach embryos representing all three reproductive modes produced and released both JH and MF, as previously shown for B. germanica, N. cinerea, and D. punctata. Members of a pair of embryonic CA from B. discoidalis, B. fumigata, R. maderae, and D. punctata were incubated with and without farnesol. MF accumulated in large amounts only in CA of R. maderae in the presence of farnesol, which indicates that control of the last step of biosynthesis of JH, conversion of MF into JH by MF epoxidase, is probably a rate-limiting step in this species.

Juvenile hormone and allatostatins in the German cockroach embryo

“…1A). JH III and MF biosynthesis from CA at 40% post dorsal closure have been reported for cockroaches from different families (although not for B. germanica), and in most cases JH III biosynthetic rates measured were more than 10-fold higher than those of MF (Li, 2007). It has been proposed that the accumulation of MF in embryos could be a consequence of the absence or inactivity of methyl farnesoate epoxidase combined with a limited oxygen supply and/or low rates of metabolism of MF, which suggests that this JH precursor may have not a specific function in the embryo Bürgin and Lanzrein, 1988;Stay et al, 2002).…”

Juvenile hormone signaling in short germ-band hemimetabolan embryos

“…We can also consider that methyl farnesoate (MF), which can bind to the JH receptor with low affinity (Jindra et al, 2015a,b), but was not measured by Maestro et al (2010), might be a possible effector of JH signaling in early embryos. MF has been detected in embryos of different cockroaches including B. germanica (Li, 2007) after the dorsal closure stage (∼45% development in most species), and titers are ≥10 times lower than those of JH. In Diploptera punctata, in which the dorsal closure exceptionally occurs at 20% development, JH and MF can be detected only from 40% development, when the CA are well formed and functional (Stay et al, 2002), but the titers of MF are ∼30 times lower than those of JH.…”

Molecular phylogeny of Blaberidae (Dictyoptera, Blattodea) with implications for taxonomy and evolutionary studies

“…Blaberid cockroaches comprise model species in research about biomimetics (e.g., Nelson et al 1997), physiology (Li 2007), sociality (Costa 2006;Pellens et al 2007) or reproductive behavior (Roth &Willis 1954;Banerjee et al 2016). These fields of research would benefit from a clear phylogenetic hypothesis or a phylogeny-derived robust classification.…”