Reciprocal Copulation of Siphopteron quadrispinosum (image) PLOS Share Print E-Mail Caption The bipartite penises, which are everted as largely translucent structures at the right front of the head (h), are reciprocally inserted into the partner. While the actual penis (p) is inserted into the gonopore (located behind the right parapod), the penile stylets (s) are hypodermically inserted into the foot of the partner. Markings are only shown for the lower animal. doi:10.1371/journal.pone.0043234.g001 Credit Citation: Lange R, Gerlach T, Beninde J, Werminghausen J, Reichel V, et al. (2012) Female Fitness Optimum at Intermediate Mating Rates under Traumatic Mating. PLoS ONE 7(8): e43234. doi:10.1371/journal.pone.0043234 Usage Restrictions Please provide proper attribution upon use. Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.