Casualty of warming: Male fertility

Christopher Davidson
November 16, 2018

During experiments, beetles, scientists have found that high temperature has a bad effect on male fertility and may cause infertility.

The offspring that males are likely to produce were halved by the heat waves and subjecting them to a second wave made the males to be nearly sterile. The insects were exposed to standard control conditions, or five-day heatwave conditions, which were five to seven degrees Celsius above what is considered their thermal optimum.

Research group leader Professor Matt Gage, of the University of East Anglia, said: 'We've shown that sperm function is an especially sensitive trait when the environment heats up.

Gage continued: "Since sperm function is essential for reproduction and population viability, these findings could provide one explanation for why biodiversity is suffering under climate change".

It should be also noted that exposure to heat waves also impacted the living span of future generations too. He added that sperm with DNA damage might still be able to fertilize females and yield offspring.

Climate change could pose a major threat to male fertility, scientists have warned, as heatwaves cause serious and long-lasting damage to sperm.

How the heat damages the sperm is not fully understood, though the researchers noticed damage to sperm membranes. But they also found that the damage was not confined to the males.

"A warmer atmosphere will be more volatile and hazardous, with extreme events like heatwaves becoming increasingly frequent, intense and widespread". Moreover, they found that the sperm from the male beetles struggled to move to the female beetles' tract.

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The results of the experiment, published in the journal Nature Communications, showed that male beetles exposed to the artificial heatwave produced half as many offspring as the males in the control group. Local extinctions are known to occur when temperature changes become too intense.

Stuart Wigby, of the University of Oxford, who was not involved in the study, said: "Given what we already know about the generality of the sensitivity of sperm to heat, there is every reason to expect that similar effects would be seen in other insects and also in mammals including humans". When males were exposed to two heatwave events 10 days apart, their offspring production was less than 1 percent of the control group.

'Our research shows that heatwaves halve male reproductive fitness, and it was surprising how consistent the effect was, ' Mr Sales said.

The research team also discovered that heatwaved dads and their sperm lived shorter lives by a couple of months. "And one answer could be related to sperm", he outlined. The study is expected to further explain why climate change is having such an impact on species populations, including climate-related extinctions in recent years.

The sons of the males who endured the heat wave produced 20 percent fewer offspring than males that had not undergone that stress.

"It is believed that beetles make up a quarter of biodiversity, the obtained results are very important for understanding how species respond to climate change".

The team hope that their findings can help inform conservation efforts.

The work was funded by Natural Environment Research Council (NERC) and the EnvEast DTP, UEA, and the Leverhulme Trust.

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