Post-testicular sperm maturation in the saltwater crocodile Crocodylus porosus: assessing the temporal acquisition of sperm motility
Brett Nixon
A B F , Amanda L. Anderson A B , Elizabeth G. Bromfield A B , Jacinta H. Martin A B , Shenae L. Cafe A B , David A. Skerrett-Byrne A B , Matthew D. Dun C D , Andrew L. Eamens A B , Geoffry N. De Iuliis A B and Stephen D. Johnston E
+ Author Affiliations
- Author Affiliations
A Priority Research Centre for Reproductive Science, School of Environmental and Life Sciences, Discipline of Biological Sciences, University of Newcastle, Callaghan, NSW 2308, Australia.
B Hunter Medical Research Institute, Pregnancy and Reproduction Program, New Lambton Heights, NSW 2305, Australia.
C Cancer Signalling Research Group, School of Biomedical Sciences and Pharmacy, Faculty of Health and Medicine, University of Newcastle, Callaghan, NSW 2308, Australia.
D Priority Research Centre for Cancer Research Innovation and Translation, Hunter Medical Research Institute, Lambton, NSW 2305, Australia.
E School of Agriculture and Food Sciences, The University of Queensland, Gatton, Qld 4343, Australia.
F Corresponding author. Email: brett.nixon@newcastle.edu.au
Reproduction, Fertility and Development 33(9) 530-539 https://doi.org/10.1071/RD20204
Submitted: 10 August 2020 Accepted: 26 November 2020 Published: 26 February 2021
Abstract
Conservation efforts to secure the long-term survival of crocodilian species would benefit from the establishment of a frozen sperm bank in concert with artificial breeding technologies to maintain genetic diversity among captive assurance populations. Working towards this goal, our research has focused on the saltwater crocodile Crocodylus porosus as a tractable model for understanding crocodilian sperm physiology. In extending our systematic characterisation of saltwater crocodile spermatozoa, in this study we examined the development of motility during sperm transport through the excurrent duct system of the male crocodile. The results show that approximately 20% of crocodile testicular spermatozoa are immediately motile but experience a gradient of increasing motility (percentage motile and rate of movement) as they transit the male reproductive tract (epididymis). Moreover, we confirmed that, as in ejaculated crocodile spermatozoa, increased intracellular cAMP levels promoted a significant and sustained enhancement of sperm motility regardless of whether the cells were isolated from the testis or epididymis. Along with the development of artificial reproductive technologies, this research paves the way for the opportunistic recovery, storage and potential utilisation of post-mortem spermatozoa from genetically valuable animals.
Keywords: crocodile, epididymis, spermatozoa, sperm capacitation, sperm maturation, sperm motility.
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