Why ‘old’ sperm might be the answer to having healthier offspring

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Researchers analysing the offspring of zebrafish from differently aged sperm showed that those conceived using ‘old’ sperm lived longer.

Is the fate of a creature’s offspring determined before it is even born? That was the focus of a study undertaken by a team from the University of East Anglia (UEA) and Uppsala University in Sweden, which monitored the performance of sperm in egg fertilisation.

Publishing to Evolution Letters, the research team’s study looked at the ejaculate of male zebrafish and found that sperm that had been around longer produced offspring with lengthier and healthier lifespans. Those offspring, in turn, then produce healthier descendants as well compared with shorter-lived sperm in the same ejaculate.

To discover this, the team performed in vitro fertilisations (IVF) by collecting gametes from male and female zebrafish and splitting the ejaculate into two halves. In one half, the team selected shorter-lived sperm and in the other those who were older.

It then added the sperm to two half clutches from a female to fertilise the eggs and reared the offspring into adulthood, monitoring their lifespan and reproductive output for a period of two years.

“Offspring sired by longer-lived sperm produce more and healthier offspring throughout their life that age at a slower rate,” said lead researcher Dr Simone Immler of UEA’s School of Biological Sciences.

“This is a surprising result, which suggests that it is important to understand how sperm selection may contribute to the fitness of the next generations.”

Unsurprisingly, these findings may have important implications for human reproduction and fertility.

“Until now, there was a general assumption that it doesn’t really matter which sperm fertilises an egg as long as it can fertilise it,” Immler said.

“But we have shown that there are massive differences between sperm and how they affect the offspring. This research has important implications for evolutionary biology and potentially beyond into areas that use assisted fertilisation technologies, for example in livestock rearing or IVF in humans.”

Colm Gorey is a journalist with Siliconrepublic.com

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