[Development of complete and bisected male genital disks after transplantation, and duration of host development inEphestia kuehniella Z.]

Complete and bisected male genital disks (HO) from larvae of the last larval instar were transplanted into full-grown (T7) larvae. In experiment A the HO were taken from T1-, T3-, T5- and T7-larvae and either implanted intact into the host larva (group A/a) or both halves of the bisected disk were transferred into a single host (group A/b). In experiment B the HO from T1-, T4- and T7-larvae were bisected and both halves were transplanted either into a single host (group B/b) or into two different hosts (group B/c).After metamorphosis of the hosts the "complete" transplants (A/a) of all age groups showed the same morphological features: qualitative differences were not observed. Within each experimental group the size of the genitalia varied considerably. However, it was found that the variation amongst the average sized genitalia of all groups was not great.After transplantation of both halves of the bisected HO (A/b, B/b) three classes of results were observed: I. each of the two halves regenerated into a complete genital organ (2r); II. only one of the halves regenerated into a complete organ (1r); III. none of the two halves regenerated the missing part (Or). Frequency of Regeneration. A/b: The frequency of regeneration (ratio 2r: 1r: Or) was the same in the age groups T1 and T3 and in T5 and T7, but the latter, older transplants regenerated more frequently than the former. B/c: In the three age groups only on part of the transplanted halves regenerated. The ratio of the regenerated halves to the non-regenerated genital organs in the three age groups did not differ significantly. Comparing the results of the groups B/c and B/b, the frequency of regeneration was found to increase by implantation of two halves in a single host. Size of the Regenerated Genital Organs. After metamorphosis of the hosts the regenerated genitalia of all groups differentiated in much the same way as "complete" transplants, but they were slightly smaller than the latter. Comparison of the size of the genitalia in exp. B showed that implantation of two halves in a single host did not influence the size of the regenerating genitalia. Duration of Development of the Hosts. The duration of further development of the hosts was neither influenced by the transplantation of "complete" disks of different age nor when the implanted halves of the bisected HO did not regenerate. On the contrary, the regeneration of implanted HO-halves caused a delay of further development in the hosts (i.e. the onset of pupation was delayed). Independently of the size and developmental stage of the disks at the time of transplantation, when only one half regenerated the average delay was almost two days as compared to the controls. An additional delay was recorded when both implanted halves had regenerated.The developmental capacities of the transplanted disks and the control of metamorphosis by regenerating disks are discussed.