New research has shown increased temperatures due to climate change is affecting the sperm level in certain insects. Researchers are concerned with the loss of sperm count in some insects could lead to massive impacts on fertility in future generations.
The research group from University of East Anglia’s School of Biological Sciences says that looking at male infertility in insects during heat waves can help explain why rising temperatures are having such a big impact on insect species.
"We know that biodiversity is suffering under climate change, but the specific causes and sensitivities are hard to pin down. 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," explains Matt Gage, the research group leader.
Sperm function devastated by increased temperatures
“Since sperm function is essential for reproduction and population viability, these findings could provide one explanation for why biodiversity is suffering under climate change. A warmer atmosphere will be more volatile and hazardous, with extreme events like heat waves becoming increasingly frequent, intense and widespread,” he continues.
“Heatwaves are particularly damaging extreme weather events. 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,” he outlined.
Females show little change
The research tea looked at the red flour beetle (Tribolium castaneum) to see how a simulated heat wave affected male reproduction ability and habits. One group of beetles were exposed to a five-day heatwave, 5°C to 7°C above their thermal optimum, another group stayed in a controlled temperature environment.
Following the five days, a series of experiments determined the potential damage to the beetle's reproductive success and sperm function. Half the beetles who experienced the heatwave could produce after and a second heatwave almost sterilized the exposed males.
However, the females of the group were mostly unaffected by the hot conditions. Although sperm inseminated inside females was also affected by the heat so affecting the female group indirectly.
Insect populations have an impact across the food chain
Kris Sales, a postgraduate researcher who led the research, said: “Our research shows that heatwaves halve male reproductive fitness, and it was surprising how consistent the effect was.” The study also found that males sexual behavior was also affected by the heat with males mating half as frequently as controls.
“Two concerning results were the impact of successive heatwaves on males, and the impacts of heatwaves on future generations,” said Sales. “When males were exposed to two heatwave events 10 days apart, their offspring production was less than 1 percent of the control group. 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.”
The researchers warn that increasing temperatures could have devastating effects on insect populations across the world, with knock-on effects to other animals populations. The study ‘Experimental heat waves compromise sperm function and cause transgenerational damage in a model insect’ was published in Nature Communications on Tuesday, November 12, 2018.