Morphogenesis of the antenna of the male silkmoth, Antheraea polyphemus. VI. Experimental disturbance of antennal branch formation

Abstract In the male silkmoth Antheraea polyphemus , the formation of the side branches of the quadripectinate antennal flagellum was disturbed by an experimental manipulation. Normally the side branches develop in the pupa via deep incisions which proceed from the periphery towards the centerline of the leaf-shaped antennal anlage. Local removal of the uppermost, pigmented cuticular layers of the pupal antennal pocket (‘cuticular window’) led to a local standstill of branch formation in the manipulated region of the pocket, most probably caused by increased evaporation of water through the remaining layers of meso- and endocuticle. These parts of the antenna retained an unbranched, plate-like shape. This early morphogenetic stage was conserved by the secretion of antennal cuticle. Besides cuticle formation, development of sensilla is not impeded by the manipulation. In the plate-shaped regions, the initial pattern formed by the sensilla in the antennal epidermis is preserved, because they maturate at their birthplaces. In the individual segments, the pattern of sensilla shows a mirror-like symmetry with respect to the segmental midline. From the edge to the midline, we found large s. trichodea , followed by small s. trichodea , s. basiconica , and s. coeloconica on the dorsal side whereas on the ventral side, there are only large s. trichodea and s. campaniformia . We conclude that the development of the featherlike antennal shape on the one hand and the development of sensilla and cuticle on the other hand are independent processes.