MORPHOGENESIS OF THE ANTENNA OF THE MALE SILKMOTH, ANTHERAEA-POLYPHEMUS .6. EXPERIMENTAL DISTURBANCE OF ANTENNAL BRANCH FORMATION

In the male silkmoth Antheraea polyphemus, the formation of the side b ranches of the quadripectinate antennal flagellum was disturbed by an experimental manipulation. Normally the side branches develop in the p upa via deep incisions which proceed from the periphery towards the ce nterline of the leaf-shaped antennal anlage. Local removal of the uppe rmost, pigmented cuticular layers of the pupal antennal pocket ('cutic ular window') led to a local standstill of branch formation in the man ipulated region of the pocket, most probably caused by increased evapo ration 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 anten nal 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 segmen ts, 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. c oeloconica on the dorsal side whereas on the ventral side, there are o nly large s. trichodea and s. campaniformia. We conclude that the deve lopment of the featherlike antennal shape on the one hand and the deve lopment of sensilla and cuticle on the other hand are independent proc esses.