Juvenile hormone signaling in short germ-band hemimetabolan embryos
Fernandez-Nicolas, A.; Bellés, X. (2017)
Development 15;144(24):4637-4644. doi: 10.1242/dev.152827
In insects, the juvenile hormone (JH) regulates metamorphosis during postembryonic development. However, the possible roles of JH in the embryo are a mystery. To shed light on this area, the expression of key elements of JH signaling in embryos of the German cockroach, a species with gradual metamorphosis, was inhibited. In different embryos, precluding the formation of the germ-band anlage, hatchability was reduced and development was interrupted in mid-embryogenesis. This contrasts with the situation in insects with discontinuous metamorphosis, like the silkworm, where the JH does not play a significant role in embryogenesis. Results suggest that loss of JH functions in the embryo may have been a significant step in the evolution from gradual to discontinuous metamorphosis.
Range of malformations observed in embryos of the German cockroach after impairing juvenile hormone signaling. A: development interrupted around the formation of the germ-band anlage. B: development interrupted around mid-embryogenesis. C: development completed, but featuring an intensely sclerotized cuticle. D: development completed, but hatching impaired. E: normally hatched nymph.