Sperm cryopreservation in an Australian skink (Eulamprus quoyii)
Rebecca J. Hobbs
A G , Rose Upton B , Leesa Keogh C , Karen James D , James Baxter-Gilbert E and Martin J. Whiting F
+ Author Affiliations
- Author Affiliations
A Taronga Institute of Science and Learning, Taronga Conservation Society Australia, Mosman, NSW 2088, Australia.
B Conservation Biology Research Group, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308 Australia.
C Office of the NSW Chief Scientist and Engineer, MLC Centre, Sydney, NSW 2000, Australia.
D Taronga Conservation Society Australia, Taronga Western Plains Zoo, Dubbo, NSW 2830, Australia.
E Centre for Invasion Biology, Stellenbosch University, Stellenbosch 7600, South Africa.
F Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
G Corresponding author. Email: rhobbs@zoo.nsw.gov.au
Reproduction, Fertility and Development 34(5) 428-437 https://doi.org/10.1071/RD21031
Submitted: 30 January 2021 Accepted: 19 July 2021 Published: 23 August 2021
Abstract
Assisted reproductive technologies for population and genetic management for threatened herpetofauna have grown substantially in the past decade. Here we describe experiments to optimise sperm cryopreservation in a model squamate, the eastern water skink Eulamprus quoyii. Small, concentrated volumes of highly motile spermatozoa were reliably collected from adult male E. quoyii by non-lethal ventral massage. Samples were used to: (1) test whether protein-rich diluents, namely Beltsville poultry semen extender (BPSE) and TES and Tris (TEST) yolk buffer (TYB), improve post-thaw quality metrics compared with Dulbecco’s phosphate-buffered saline (DPBS); and (2) compare the efficacy of these diluents in combination with either 1.35 M glycerol or 1.35 M dimethyl sulfoxide (DMSO) at two freezing rates, fast (approximately –20°C min−1) versus slow (–6°C min−1). Glycerol and DMSO performed equally well in preserving spermatozoa under slow freezing rates. Under these conditions, the use of the complex diluents BPSE and TYB significantly improved post-thaw total motility compared with DPBS. Complex interactions occurred between cryodiluent type, cryoprotectant and freezing rate when testing fast versus slow freezing rates among treatment groups. Under slow freezing rates, DMSO was better at preserving membrane integrity and motility, regardless of diluent type, but successful fast freezing required complex diluents to support motility and membrane integrity, which has implications for implementation in a field setting.
Keywords: conservation breeding programs, controlled-rate freezing, dry shipper, genome resource bank, reptile, spermatozoa, wildlife.
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