METAMORPHOSIS OF IMAGINAL DISKS OF HOUSEFLY - EVAGINATION OF TRANSPLANTED DISKS

A new technique for transplanting imaginal disks of the housefly is described. When prepupal disks are transplanted superficially (surface transplantation) just beneath the puparium in early prepupal hosts, they evaginate synchronously with the host's organs and differentiate normally like the disks developing in situ. Histological evidence indicates that cells from the peripheral region of the disks migrate and join the epidermis of the host. This facilitates continuation of morphogenetic events culminating in eversion of the transplant. The significance of the cellular contact with epidermal cells of the host is discussed. A well developed nerve from the transplanted leg joins the thoraco‐abdominal ganglion of the host. Flexion of the terminal leg segments indicates the presence of motor fibers innervating muscles in the leg. Disks from late third instar larvae and young prepupae evaginate whereas disks from younger third instar larvae fail to evaginate when surface transplanted. Disks, from all types of donors, cultured in adult abdomens fail to evaginate when retransplanted in prepupae. These and other results suggest that hormones may induce or inhibit morphogenetic cell movement in imaginal disks. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company