Ultrastructural observations on sperm storage in the ovary of the platyfish, Xiphophorus maculatus (Teleostei: poeciliidae): the role of the duct epithelium.

Sperm storage is an important phenomenon occurring in viviparous and oviparous teleosts and contributes to the reproductive life history of these forms. There is a paucity of morphological studies on sperm storage in fishes. The majority of these have been confined to the light level of investigation. In this report, we describe, at the ultrastructural level, sperm storage in the viviparous platyfish, Xiphophorus maculatus. Female platyfish, as is typical of the poeciliids, are capable of storing viable sperm for up to several months within the ovary and gonoduct. We observed that sperm stored within inseminated platyfish became associated with specific epithelial cells (SACs) lining the oviduct. Two forms of association were seen: 1) sperm were found within deep surface pits and pockets, and 2) the spermatozoa were taken up and incorporated within the cytoplasm of the SACs. Junctional complexes in the form of tight junctions (zona occludens) and desmosomes at the apico-lateral surfaces of the SACs were prevalent. The junctions could have contributed to allograft survival of the haploid heterogenetic sperm cells within the female's reproductive tract. Our results shed light on the mechanism of sperm storage in the platyfish and could serve as a model for other poeciliid species and teleosts that are capable of storing sperm. Copyright 2000 Wiley-Liss, Inc.