Die zytologie der Bastarde aus der Kreuzung parthenogenetischer Weibchen vonSolenobia triquetrella F. R. mit Männchen der bisexuellen Rasse

Summary

• 1. In crosses of diploid parthenogeneticSolenobia triquetrella ♂x♀ of the bisexual race sexual mosaic individuals appear regularly, although in small number. In the present paper they are investigated morphologically and as far as possible cytologically and experimentally.

• 2. The most simple case is that they are gynandromorphs of an XO:XX constitution. They originate during pure parthenogenesis, but this type of sexual mosaic can also originate in the F₁ of crosses as described under 1.

• 3. All other sexual mosaics are individuals composed of body parts with normal sexual constitution (XX or XO) and of parts which are doublessly intersexual in nature.

• 4. The intersexes which have been previously investigated (Seiler, 1966) were all triploid. For this reason we assume that the intersexual body parts of the present sex mosaics are also triploid, i.e. have a 3n constitution. A direct cytological proof has not been reached but we have evidence which clearly points towards triploidy.

• 5. It is characteristic for these mosaic individuals that they are gynandromorphic in appearance, in the sense that they may be for example XX or XO on one side of the body and intersexual (3n) on the other. At least larger parts of the body or groups of segments are different on the right and the left.

• 6. We have found and analysed morphologically the following constitutions:$\begin{gathered} \left. \begin{gathered} a) XX :3n \hfill \\ b) XX :3n,XO,XX \hfill \\ c) XX,3n:3n \hfill \\ \end{gathered} \right\} 10 \times \hfill \\ \left. \begin{gathered} d) XO :3n,XO \hfill \\ e) XO,3n :XX or 3n \hfill \\ f) XX,3n:3n,XX \hfill \\ \end{gathered} \right\} 3 \times \hfill \\ \end{gathered}$

  In addition the pure gynanders:$\left. {g) XX :XO } \right\}3 \times$

• 7. Parthenogenesis of the automictic meiotic type inTriquetrella starts from the „Richtungskopulationskern” (R.K.K.), the fusion product of the two inner polar bodies. By fusion of daughter nuclei of the egg nucleus diploid nuclei are formed, but these are prevented from further development by the R.K.K.

• 8. This blockage by the R.K.K. is, however, not an absolute one; occasionally the automictic derivative of the egg nucleus dominates and blocks itself the R.K.K. This leads to the appearance of exceptional males.

• 9. If as an exception in a parthenogentic egg neither the R.K.K. blocks the egg nucleus nor vice versa, a gynandromorph ensues. If both types of nuclei are present from the beginning of cleavage, and if both types proliferate, one side of the body is of one sex and the other side of the other.

• 10. As a rule, in the inseminated parthenogenetic egg the amphimictic egg nucleus blocks the R.K.K. In exceptional cases however, both types of nuclei may develop, an event which also leads to gynanders, provided the blockage is absent from the very beginning.

• 11. We assume that sexual mosaics with triploid body parts appear as a consequence of a fertilization of both, the female pronucleus as well as the R.K.K. By this mode the 2n:3n mosaics originate; they are gynandromorphic in appearance whenever development proceeds from the start with 2n and 3n nuclei.

• 12. If progeny of the R.K.K. is fertilized after cleavage has begun, complicated mosaics ensue which can be XO:3n, XO or XO:3n, XX etc.

• 13. If one assumes that double fertilization can occur, all mosaics can be explained, which have been encountered.

• 14. Double fertilization has been assumed to be the cause for the development of sex mosaics in other lepidoptera e.g. inBombyx mori andLymantria dispar.

• 15. We specifically investigated the exceptional males and those males which originated from parthenogenetic eggs of F₁ females from crosses as described under 1.; we were able to show by cytological and exprimental means that these are normal males.

• 16. Finally is was shown that in the F₁, F₂ and in back crosses the spermatogenesis of all these bastards is normal. This explains why diploid parthenogenesis can be retransformed to the original bisexual form.