Plasma and acrosomal membrane lipid content of saltwater crocodile spermatozoa
R. R. Miller
D E * and B. Nixon C *
+ Author Affiliations
- Author Affiliations
A Department of Biology, Hillsdale College, 33 E. College Street, Hillsdale, MI 49242, USA.
B Controls Group, Limbach Company, 926 Featherstone Street, Pontiac, MI 48342, USA.
C Priority Research Centre for Reproductive Science, School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia.
D School of Agriculture and Food Sciences, The University of Queensland, Gatton, Qld 4343, Australia.
E Corresponding author. Email: s.johnston1@uq.edu.au
Reproduction, Fertility and Development 33(9) 596-604 https://doi.org/10.1071/RD21007
Submitted: 12 January 2021 Accepted: 01 April 2021 Published: 4 May 2021
Abstract
This study describes the chemical lipid composition of the sperm plasma and acrosomal membranes of the saltwater crocodile Crocodylus porosus with the aim of providing new insights into sperm physiology, particularly that associated with their preservation ex vivo. The specific fatty acid composition of the sperm plasma and acrosomal membranes is documented. The mean (± s.d.) ratio of unsaturated to saturated membrane fatty acids within the plasma membrane was 2.57 ± 0.50, and was determined to be higher than a similar analysis of the lipids found in the acrosomal membrane (0.70 ± 0.10). The saltwater crocodile sperm plasma membrane also contained remarkably high levels of cholesterol (mean (± s.d.) 40.7 ± 4.5 nmol per 106 sperm cells) compared with the spermatozoa of other amniote species that have so far been documented. We suggest that this high cholesterol content could be conferring stability to the crocodile sperm membrane, allowing it to tolerate extreme osmotic fluxes and rapid changes in temperature. Our descriptive analysis now provides those interested in reptile and comparative sperm physiology an improved baseline database for interpreting biochemical changes associated with preservation pathology (e.g. cold shock and cryoinjury), epididymal sperm maturation and capacitation/acrosome reaction.
Keywords: cholesterol, fatty acids, plasma membranes acrosomal membranes, saltwater crocodile.
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