Infertility | Does Crocodile sperm provides insights into male infertility?
Male infertility is affecting about 1 out of 20 men in Australia. According to the findings which were published in the Royal Society Journal Proceedings B could help in the search for causes of male human infertility. Researchers say that crocodile sperm is more like human sperm than scientists previously thought. Dr Brett Nixon, a reproductive biologist at the University of Newcastle and lead author of the study said that now scientists are hoping to use the crocodile as a model for understanding sperm function at a basic level, and see whether we can apply that to get a better result on infertility among humans. This research could also help improve commercial breeding and conservation of crocodiles. Dr Nixon said in many cases of male infertility occurs due to defective sperm.
In normal cases of development, human sperm emerge from the testis in an immature form and must be exposed to certain conditions in the male and female reproductive tracts before it is capable of fertilization. They look a like normal sperm but they have the lack of ability to swim and lack of ability to recognize an egg and participation in fertilization. According to Dr Nixon, till now this process was unique of sperm maturation to mammals. Dr Nixon adds that first it was widely believed that crocodile sperm is similar to birds sperm, in which sperm comes out of the testes and are immediately able to fertilize. But now according to this new study of sperm from Australian saltwater crocodiles, Dr Nixon and team have found otherwise. They say, the sperm of crocodile do undergo functional changes after they leave the testis. The team collected crocodile sperm from sedated Australian saltwater crocodiles and incubated it under various conditions that mimicked the female reproductive tract.
Dr Nixon said, they identified a handful of proteins that are involved in enabling the sperm to move and recognize eggs. These proteins are also present in human sperm and could provide targets for infertility research. According to researchers, they believed they have identified a chemical switch, in the form of bicarbonate ions in the female reproductive tract that are able to that activate the proteins. The low level of bicarbonate the proteins makes the sperm’s tail move in a whip, but when the bicarbonate level rise up, it increases the levels of a biological molecule called cyclic-AMP, which stimulates the proteins. Dr Nixon said, Cyclic-AMP also changes the surface of the eggs so it recognizes eggs. He said that it is a well known fact that bicarbonate levels rise up in humans during ovulation but this is the first time that it’s found in crocodiles.
Research will help crocodile conservation
This research is not only helpful in human infertility research but it explains the mystery of how the American alligator stores sperm for several months in the female reproductive tract. The sperm experience an environment that is low in bicarbonate initially but then upon ovulation, we anticipate there would be a spike in bicarbonate that would reactivate the sperm and then they would be able to fertilize the eggs. Storing sperm in female reproductive tract ensures that sperm is available when ovulation occurs and also to fertilize different eggs in a clutch using sperm from different males. Dr Nixon adds that this research will also help in storing crocodile sperm for conservation or breeding purposes. Low level of bicarbonate could be used to “silence” the sperm and ensure that it does not exert its energy until it is required for fertilization.