Development of a penis from the vestigial penis in the female apple snail,Pomacea canaliculata

In the apple snail (Pomacea canaliculata), females have an undifferentiated mass of tissue near the anus. Although this mass is called the vestigial p enis, there are no signs of a hermaphroditic gonad or any structure that re presents a transition from one sex to the other. Based on considerations of the steroid hormone theory of reproduction and in view of disruption of en docrine systems in molluscs by organotins, a study was made of the effects of tributyltin on female snails. Exposure to tributyltin resulted in the so -called imposer phenomenon, and both a penis and a penis sheath were newly generated from the so-called vestigial penis. The same phenomenon was also induced by testosterone. Thus the vestigial penis, named more than one hund red years ago, has been demonstrated for the first time to be a rudiment of the penis itself.