Coordinated development of the male and female reproductive systems in the cestode Hymenolepis microstoma

BackgroundCestodes have complex hermaphroditic reproductive systems that produce massive numbers of eggs. This reproductive output is made possible by the continuous production of serially repeated sets of reproductive systems (proglottids). However, their reproductive development remains poorly understood. ResultsWe characterized reproductive development in the model cestode Hymenolepis microstoma by analyzing markers of cell proliferation, meiosis, and differentiation along the series of proglottids. Reproductive development begins with the formation of a central genital primordium, from which the reproductive ducts and gonads differentiate. Development is proterandrous, and testicular development is prolonged. In contrast, female reproductive development occurs over a short interval and is characterized by the coordinated differentiation of the ovary and vitelline gland. Entry of oocytes into meiosis is almost synchronous, and paralleled by cell proliferation in the vitelline gland. Subsequent growth of arrested oocytes and differentiation of vitelline cells occur in parallel. Insemination coincides with the onset of ovarian meiosis, indicating a close temporal coordination between male and female reproductive development. Finally, we show that gametogenesis and insemination proceed in adult worms maintained in vitro. ConclusionsOur findings show the coordination of reproductive development in a self-fertile hermaphrodite, and provide an experimental system for studying reproductive development in cestodes.