Heatwaves can 'wipe out' male insect fertility

[nitpicker]

https://www.theguardian.com/environment/2018/nov/13/heatwaves-wipe-out-male-insect-fertility-beetles-study

Heatwaves can 'wipe out' male insect fertility

Study of beetles could explain global decline – and also be a warning to humankind

Damian Carrington Environment editor

Tue 13 Nov 2018 10.00 GMT


Heatwaves severely damage the fertility of male beetles and consecutive hot spells leave them virtually sterilised, according to research. Global warming is making heatwaves more common and wildlife is being annihilated, and the study may reveal a way in which these two trends are linked. The scientists behind the findings said there could also be some relevance for humans: the sperm counts of western men have halved in the last 40 years.

Researchers studied beetles because their 400,000 species represent about a quarter of all known species. Insect populations are plunging worldwide as temperatures rise, falling by about 80% in 30 years in Puerto Rico’s rainforest and by 75% in German nature reserves.

Insects are such an integral part of life, as pollinators and prey, that scientists say their decline could lead to “ecological Armageddon”. Little is known about the precise causes of the decline, though climate change, habitat destruction and global use of pesticides are considered probable factors.

The research, published in the Nature Communications journal, found that exposing beetles to a five-day heatwave in the laboratory reduced sperm production by three-quarters; females were unaffected.
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The red flour beetle used in the experiments is a tropical species that thrives at 35C. When exposed to temperatures of 5C and 7C higher, male fertility plummeted. While these were high temperatures, 90 countries had experienced them in recent years, said Gage.

After being exposed to a heatwave, the number of offspring produced by males fell by half. Even more worryingly, harmful effects were inherited by the males they produced – their lives were 20% shorter and they in turn produced fewer offspring.

The most extreme impact was in male beetles exposed to two heatwaves 10 days apart – their offspring production fell by 99%. “It kind of wipes them out,” Gage said.
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