Ecdysteroid Titres and Cuticle Depositions in Embryos of the DipteranCalliphora erythrocephala

Publisher Website
Google Scholar
Abstract
Before the shortening of the germ band, embryos of Calliphora erythrocephala secrete an electron dense layer which resembles a thin atypical cuticle. After completion of the dorsal closure, a second, typical, cuticle is deposited. It is characterized by a thick procuticle and by the presence of hooked setae. This cuticle develops into the larval cuticle of the first instar. We did not find in newly-laid eggs of Calliphora detectable amounts of either free or hydrolysable conjugated ecdysteroids. A marked rise in ecdysteroid concentrations, essentially attributable to free ecdysone and 20- hydroxyecdysone, occurs shortly before the deposition of the typical cuticle. After a transient decrease, the ecdysteroid titre rises again before hatching. When eggs are mid-ligatured at blastula or early gastrula stages, the posterior embryonic half is able to build up a typical cuticle with hooked setae. This cuticulogenesis is therefore not dependent on the presence of the embryonic ring glands.