Acknowledgments
We thank Roberto Joachim for assistance in the laboratory and two anonymous reviewers for helpful suggestions on earlier versions of this manuscript. This work was funded by a Rice Creek Associates Small Grant to CHC, a European Research Council Starting Grant (FP7/2007-2013 grant 260729 EndoSexDet) to R.C. and intramural funds from the Centre National de la Recherche Scientifique and the French Ministère de l’Education Nationale, de l’Enseignement Supérieur et de la Recherche.