SPERM DISPLACEMENT IN A MILLIPEDE - AN INVESTIGATION INTO THE GENITALMORPHOLOGY OF THE SOUTHERN AFRICAN SPIROSTREPTID MILLIPEDE ORTHOPORUS-PYRHOCEPHALUS

Male and female genital morphology of the spirostreptid millipede Orth oporus pyrhocephalus was examined by conventional and scanning electro n microscopy techniques. The relative syncopulatory positions of the g enitalia were established through dissections of pairs in copula. Male gonopods bear scoops and regions of pitted spines, both of which are similar in form to morphological structures implicated in insect sperm displacement. Consideration of the position of the oviduct-spermathec al junction in females predicts that displacement is restricted to a s perm removal mechanism. The importance of spermathecal shape in determ ining sperm precedence patterns is discussed. The orientation of the g enitalia during copulation indicates that sperm displacement is plausi ble and a mechanism of gonopod action is suggested.