Too hot to handle: investigating birds’ heat tolerance sheds light on their ability to adapt to climate change

A Gambel’s quail (Credit: Dick Daniels. CC BY 3.0)

In January 2014 more than 100,000 megabats died in the Australian state of Queensland. The cause? Heat.

That summer, a heatwave passed through Queensland causing temperatures to reach highs of nearly 45°C (113°F). Unable to cope with the extreme heat and subsequent dehydration, megabats, or flying foxes as they’re known locally, started dropping from the sky. On one extremely hot day, researchers recorded at least 45,500 dead bats in southeast Queensland.

“Most of the stuff you read about on climate change [talks about] average monthly temperature or average annual temperature rising by two degrees. But what’s also going to happen is the occurrence of extreme events is going to increase—in frequency and in intensity,” says Dr. Alex Gerson, an assistant professor in the department of biology at the University of Massachusetts, Amherst. “So what’s a desert going to look like in 100 years? Is it going to be devoid of birds completely or is something going to be able to make it?” Continue reading


Asymptomatic dengue-infected humans can transmit the virus to mosquitoes

A drawing of a female Aedes aegypti mosquito (Credit: E.A. Goeldi)

An estimated 3.9 billion people in 128 countries are at risk of dengue virus infection. Of the estimated 390 million dengue infections that occur each year, 96 million will manifest clinically with flu-like symptoms including fever, headache, nausea and muscle and joint pain. Unlike the flu virus, dengue virus cannot be transmitted directly from person to person. It instead relies on an insect vector, the mosquito Aedes aegypti. Female mosquitoes contract the virus when they bite and feed on an infected human. After a period of four to ten days, the virus disseminates to various tissues in the mosquito, where it remains for the rest of the mosquito’s life. At this point, the mosquito is infectious and can transmit the virus through its saliva and bite.

Earlier studies showed that the time during which dengue virus-infected humans can transmit the virus to mosquitoes coincides with the onset of clinical symptoms and an increase in viral load in their blood. These observations led to the assumption that infected, asymptomatic humans are so-called “dead-end hosts” for the virus because their viral levels are so low as to make them noninfectious to mosquitoes, essentially breaking the transmission chain.

In a new paper published last week in the Proceedings of the National Academy of Sciences, an international group of researchers challenged a long-held assumption that asymptomatic patients infected with the dengue virus are not infectious. The team sought to experimentally test the assumption that asymptomatic people are noninfectious and to determine how human-to-mosquito transmission varied with timing of symptom onset. Continue reading

Resistance to plant toxins in milkweed butterflies is linked to toxin storage for defense

A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)
A monarch caterpillar feeding on milkweed (Credit: OakleyOriginals. CC BY 2.0)

When your only food source also contains a deadly poison, your options are pretty limited: either find a new food source or find some way of making the poison less toxic. This is exactly the situation that many plant-eating insects find themselves in, particularly those that eat milkweed.

Milkweeds produce a class of chemical toxins named cardenolides. These compounds specifically bind and inhibit the sodium potassium pumps found in heart muscle cells. Without working pumps sodium levels in the cell rise, setting off a chain of events that ultimately disrupt muscle contraction in cardiac tissue. At a high enough dose, these heart-stimulating effects can be lethal to insects, humans and animals in between. How then do insects that depend on milkweed as their main food source cope with this hidden poison? Continue reading