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Fruitful Discovery

photography by Mckenzie James

An international team of researchers, including a York University scientist, have found that fruit flies – those pesky insects that buzz around your bowl of overripe bananas – have a surprising ability to adjust to quick drops in temperature. They do this by radically altering their gene expression and metabolism in response to sudden temperature changes in their environment.

So, what’s the big deal? Well, understanding how insects tolerate sudden changes in temperature could be a crucial step in both protecting and controlling insects worldwide, says Heath MacMillan, a Banting Postdoctoral Fellow at York. He led the study in conjunction with researchers in Canada, Switzerland and Japan.

With the world’s unpredictable pattern of climate change, the need to understand how insects are affected by rapid temperature fluctuations is becoming increasingly important, since they make up more than 75 per cent of all animal species. “Temperature is one of the strongest predictors of the global distribution of insect species,” says MacMillan. “This is because temperature affects all aspects of insect physiology, and limits the ability of insects to move, eat and reproduce.”

Insects modify their physiology and behaviours to respond to temperature so they can continue to function, even at very low ones. This ability is necessary to survive cold ­winter months, but the process of how insects do it is not well understood.

While many insects are disease carriers, many others are beneficial to crops (e.g. pollinators), so understanding insect physiology improves our ability to predict changes in insect populations as the Earth’s climate continues to change rapidly.

An image of a male fruit fly
Chilling out: A male fruit fly stands on the steel surface of a cooling apparatus as York scientists study the physiological mechanisms that allow him to sense temperature changes and tolerate the cold

For the study, researchers raised common fruit flies, Drosophila melanogaster, from eggs through to their larval or maggot stages, at room temperature (21 C). Once they were adults, half of the flies were transferred to live at 6 C.

“The flies responded to this change by changing the expression of genes and proteins in their bodies, which in turn impacts on the metabolic pathways they use,” says MacMillan. “After six days of keeping the two groups of flies at 21 and 6 C, we sampled all of them and measured the expression of every one of their genes and the abundance of every metabolite, or chemical, in the flies that we could identify.”

The researchers expected to see changes in the flies that were exposed to the cold, but were surprised by the extent of them. Nearly a third of their genes increased or decreased in expression, and the abundance of roughly half of their metabolites (the products of metabolic reactions) changed at the same time. Researchers plan to use this information to examine specifically how the genes and metabolites identified in the study contribute to insect survival in the cold.

The ultimate goal is complete understanding of cold tolerance. If scientists are successful, that could help with the development of new applications in the realms of agriculture and disease transmission.

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