Potential sperm storage structures in the Poeciliopsis fish ovary

Schimmel/Conrades Science Center Atrium

Previous research suggests that viviparous fish species have unique structures for sperm storage, which are important for internal fertilization. Here we study live-bearing fish from the genus Poeciliopsis to better understand the anatomy of structures involved in sperm storage. Species in Poeciliopsis are somewhat unique in that they have varying degrees of placentation based on the amount of post-fertilization maternal nourishment. Lecithotrophs, such as Poeciliopsis gracilis, have no postfertilization maternal nutrient provisioning in which developing embryos receive nutrients from the yolk, while matrotrophs, such as Poeciliopsis prolifica, have continued additional post-fertilization maternal nutrient provisioning. Poeciliopsis species also have superfetation where there are various stages of embryonic development occurring together in time and within in a single ovary. Various morphological structures have likely evolved in order to store sperm so that this process may occur. The goals of this project are to (a) perform an extensive literature search on sperm storage in fish and (b) examine ovarian histological slides for sperm storage structures of Poeciliopsis gracilis and Poeciliopsis prolifica. Based off of the literature work in different viviparous fish, both Poeciliopsis species examined suggest the presence of different ovarian structures involved in housing sperm and potentially storing sperm for long periods of time.