Tuatara sperm is “three times longer and faster” than human sperm, researchers have discovered – with the findings being used to help the survival of the species.
In late September researchers from Victoria University of Wellington released their findings after researching the ancient reptile’s reproductive habits.
They found that tuatara sperm was not only longer but also faster than what human males have.
Speaking to 1News, visiting researcher and author of the project Sarah Lamar believed this was because male tuatara don’t have reproductive organs – mating pairs just rub their cloacas together. But there is no definitive answer yet.
“They don't have any sperm delivery organ,” she said.
“Sperm dies when it's outside of the ideal environment. It wants to be inside the body it’s made for.
“So perhaps they have really fast sperm to help them get from the outside of the cloaca, where they're deposited, because they kind of have this common opening with females, like one general hole.
“It's really interesting because it's probably quite an expensive thing for the body to make cells that move that fast.”
Lamar described the cells as being “threadlike”, looking very different to mammal sperm and three times longer than human sperm.
“It doesn't look like what you would expect. When I looked at it under a microscope for the first time, I was like, ‘Is that the sperm?’”
“It kind of looks more like a bird sperm, which I guess makes sense.”
Despite the size and speed of the reptiles’ reproductive cells, they have very low birthrates – largely coming down to infertile males and the frequency with which females lay eggs.
Lamar said that only 20% of males in a population are able to secure a mate, being the competitive “big boys” of a population. Often, females will only give birth every four years.
While the most competitive males are able to secure a mate, it doesn’t necessarily mean they are fertile.
“It now changes the conversation where we assume that, just because a male falls into this top 20%, doesn't actually mean that he is fertile and can secure more opportunities."
She hopes that her research will be able to help boost the population both in the wild and in captivity.
“And when we start new populations, and when we translocate individuals, translocating is always a really big decision because it could have animal welfare implications for that individual.”
“So when we move, we want to make sure that they're going to be reproducing and thriving.”
Lamar also hopes that it will help those facilitating tuatara reproduction in the wild and captivity to find males who are healthy and fertile.
“I think that it will change the formula for how we choose the number of individuals, or maybe just test them before we move them, just to make sure that that's true, and that they aren't gonna be able to reproduce.
“Or if we're seeing low levels of fertile eggs in the wild, we know now that actually, some of the males are often infertile.”
Tuatara are currently listed as “at risk-relict”, once living across mainland Aotearoa, but now they only exist on 32 islands in the wild. Threats include rats, mice, habitat destruction, poaching and low genetic diversity.
They are the last survivors of reptiles that once thrived during the age of the dinosaurs, and they live for around 60 years - but can reach 100 in some cases.
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