AsianScientist (May 11, 2016) – Like human sperm, Australian saltwater crocodile sperm continues to mature outside the testes, behaving differently from what was previously thought. The finding, published in Proceedings of the Royal Society B, has significant implications for both human fertility and animal conservation.
The study was led by Associate Professor Stephen Johnston from the University of Queensland School of Agriculture and Food Sciences, who is an expert in artificial insemination technology, in collaboration with colleagues from the University of Newcastle.
“We can gain important insights into human sperm by studying the less complicated sperm of other species. The study of crocodile sperm has enabled us to identify key proteins involved in motility and we can manipulate the activity of these proteins to increase the ability of sperm to swim and ultimately fertilize an egg,” said Professor Brett Nixon from the University of Newcastle.
Approximately one in 20 men experience fertility issues; however only one in 100 produce no sperm at all. Nixon said the research could have significant implications for assisted reproductive technologies.
“Human sperm only becomes fully mature and capable of fertilizing an egg during its journey through and interaction with the female genital tract, so its ability to make that journey or ‘swim’ is crucial. We are studying the activation of key proteins associated with ‘swimming’ ability,” Nixon said.
The research could also have major implications for the conservation of endangered crocodiles, almost half of which are currently listed as vulnerable or endangered species. As crocodile breeding habits and gender are temperature dependent, a warming climate could result in the birth of only female crocodiles.
“A nest temperature of 32-33 degrees Celsius results in male offspring. Anything below or above tends to favor female hatchlings and may also be associated with higher mortality rates, so a warmer climate could have serious consequences for crocodiles,” he added.
The research will help to assist captive breeding programs, offering a buffer against climate change-related threats, and help to improve genetics for commercial crocodile farmers, similar to the cattle industry.
Crocodile semen for study was collected by Johnston using a digital massage technique that he has pioneered.
“I’m no Crocodile Dundee—wrangling four-meter long saltwater crocs is not something I envisioned myself doing when I started out in this field,” Nixon said.
“Gratefully, my research partner Stephen and the Koorana crocodile farm take care of this part of the process.”
The article can be found at: Nixon et al. (2016) The Australian Saltwater Crocodile (Crocodylus porosus) Provides Evidence That the Capacitation of Spermatozoa May Extend Beyond the Mammalian Lineage.
Source: University of Queensland; Photo: cath91800/Flickr/CC.
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