Figure 1

Morphological changes in thoracic dorsum during molting. Thoracic dorsum development in the honeybee during the ecdysteroid-regulated pupal-to-adult molt. Ecdysteroid titer modulation adapted from Pinto et al.[41]. Photos of bees in the sequential phases of the pupal-to-adult molt are shown. The abbreviations in bold under the photos represent the developmental phases used for gene expression analysis: Pw (newly-ecdysed-pupa), Pp (pupa-in-apolysis) and Pbl (pharate-adult). Apolysis is triggered in the Pp phase by the ecdysteroid peak. Deposition and differentiation of the adult exoskeleton occurs under declining ecdysteroid titer in the successive pharate-adult phases (Pdp, Pb, Pbl, Pbm and Pbd). NE: newly-emerged worker bee. Toluidine blue-stained semithin sections of the thoracic dorsum from pupae-in-apolysis (Pp phase), and pharate-adults (Pb and Pbl phases) are shown at the bottom. The detached pupal cuticle (arrowheads) is evident in pupae-in-apolysis (Pp phase) and pharate-adults (Pb phase). Muscle precursors and abundant fat body cells could be observed in pupae-in-apolysis (Pp phase). Adult cuticle deposition on epidermis (arrowheads), and differentiating muscle fibers interspersed with fat body cells were seen in early pharate-adults (Pb phase). The fat body cells disappear from the thoracic dorsum and muscle fibers contact epidermis in the next pharate-adult phase (Pbl).