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Global warming is cooking sperm and could threaten male fertility

Nov. 13 (UPI) — Heatwaves are frying the sperm inside insects, according to a new study.

The findings, published Tuesday in the journal Nature Communications, could help explain why biodiversity continues to decline as the planet warms.

“We’ve shown in this work that sperm function is an especially sensitive trait when the environment heats up, and in a model system representing a huge amount of global biodiversity,” Matt Gage, researcher at the University of East Anglia, said in a news release. “Since sperm function is essential for reproduction and population viability, these findings could provide one explanation for why biodiversity is suffering under climate change.”

Plants and animals can adapt to environmental changes, but studies suggests rapid changes in temperature can trigger sudden extinctions.

“Heatwaves are particularly damaging extreme weather events,” Gage said. “Local extinctions are known to occur when temperature changes become too intense. We wanted to know why this happens. And one answer could be related to sperm.”

To understand the impacts of warming on fertility, scientists exposed red flour beetles, Tribolium castaneum, to simulated heatwave conditions. The lab experiments showed heatwaves, featuring temperature 5 to 7 degree Celsius above the species’ thermal optimum, cut the number of beetle offspring in half. When beetles were exposed to a second heatwave, males nearly became sterile.

“When males were exposed to two heatwave events 10 days apart, their offspring production was less than 1 percent of the control group,” said Kirs Sales, a postgraduate researcher. “Insects in nature are likely to experience multiple heatwave events, which could become a problem for population productivity if male reproduction cannot adapt or recover.”

When females affected by the heatwave were allowed to mate with males unexposed to heat, reproductive success returned to normal, suggesting sperm are harmed by rising temperatures.

The damage caused by the heatwave affected the sons of overheated males. Subsequent male generations also produced fewer offspring. Previous studies have shown the genetic and physiological impacts of environmental change can be passed down from one generation to the next — as can tolerance for change.

While the latest findings focused on beetles, similar studies suggests heat can damage male fertility in warm blooded animals. Heat’s impact on fertility could alter the dynamics of entire ecosystems.

“Beetles are thought to constitute a quarter of biodiversity, so these results are very important for understanding how species react to climate change,” Sales said. “Research has also shown that heat shock can damage male reproduction in warm blooded animals too, and past work has shown that this leads to infertility in mammals.”

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