Modification of sperm morphology during long-term sperm storage in the reproductive tract of the Chinese soft-shelled turtle, Pelodiscus sinensis.

Linli Zhang,Xiaowu Chen,Qian Zhang,Qiusheng Chen,Ping Yang,Wei Chen,Yi Liu,Xunguang Bian,Shuai Wang,Yasir Waqas,Shakeeb Ullah,Yuan Le,Bing Chen

doi:10.1038/srep16096

Abstract

Sperm storage in vivo extends the time window for fertilisation in several animal species, from a few days to several years. The underlying storage mechanisms, however, are largely unknown. In this study, spermatozoa from the epididymis and oviduct of Chinese soft-shelled turtles were investigated to identify potentially relevant morphological features and transformations at different stages of sperm storage. Large cytoplasmic droplets (CDs) containing lipid droplets (LDs) were attached to the midpiece of most spermatozoa in the epididymis, without migrating down the sperm tail. However, they were absent from the oviductal spermatozoa, suggesting that CDs with LDs may be a source of endogenous energy for epididymal spermatozoa. The onion-like mitochondria recovered their double-membrane morphology, with typical cristae, within the oviduct at a later stage of storage, thus implying that mitochondrial metabolism undergoes alterations during storage. Furthermore, a well developed fibrous sheath on the long principal piece was the integrating ultrastructure for glycolytic enzymes and substrates. These novel morphological characteristics may allow turtle spermatozoa to use diverse energy metabolism pathways at different stages of storage.

Highlights

Sperm storage in vivo extends the time window for fertilisation in several animal species, from a few days to several years
In the female reproductive tract have been performed in mammalian systems, in which sperm storage times are limited[9]
Based on the reproductive cycle of this turtle, sperm storage in the oviduct can be divided into three stages: early, intermediate and late

Summary

Introduction

Sperm storage in vivo extends the time window for fertilisation in several animal species, from a few days to several years. A well developed fibrous sheath on the long principal piece was the integrating ultrastructure for glycolytic enzymes and substrates These novel morphological characteristics may allow turtle spermatozoa to use diverse energy metabolism pathways at different stages of storage. Sperm storage is a reproductive strategy widely used by animal species that extends the longevity of spermatozoa until the opportunity for fertilisation occurs. This in turn increases the likelihood of successful fertilization, in some insect, fish, amphibian and reptile that store spermatozoa in vivo within the female reproductive tract for long periods (up to months and years)[1,2,3]. After mating activity and ovulation between June and August, the spermatozoa are stored in the oviduct until used to fertilise eggs the following year

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Discussion

Conclusion