Plasma and acrosomal membrane lipid content of saltwater crocodile spermatozoa

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.

Common goals, different stages: the state of the ARTs for reptile and amphibian conservation

“…The authors conclude that future studies are needed on fundamental anatomy, physiology and behaviour of females in particular, a point applicable to all the reptile groups. Nixon et al (2021aNixon et al ( , 2021b and Miller et al (2021) contributed three studies on fundamental reproductive physiology for the saltwater crocodile, ranging from posttesticular sperm maturation and gross and micro-anatomy of the male reproductive duct (Nixon et al 2021a(Nixon et al , 2021b to characterising the chemical lipid composition of the sperm plasma and acrosomal membranes (Miller et al 2021). Sandmaier et al (2022) also contributed a study characterising sperm production in a male Philippine crocodile, further filling knowledge gaps in crocodilians.…”