https://m.kekenet.com/broadcast/201903/580537.shtml
This is Scientific American — 60-Second Science. I'm Marissa Shieh.
One of the delights of summer is to see monarch butterflies dancing through the air. But it's becoming harder to see them in certain locales—in some places the population has dropped by as much as 90 percent. And climate change may make life even more challenging for these charismatic insects. That's because higher carbon dioxide levels can lower the amount of toxins in milkweed—the monarch caterpillar's food. The caterpillars use those toxins to protect themselves from a deadly parasite that produces spores.
"When the caterpillars are really small...those spores get into the monarch's gut and they break apart and they start drilling holes in the gut lining and reproducing and just doing nasty parasite things that are bad for the monarchs."
Leslie Decker, an ecologist at Stanford University. Decker and her colleagues raised hundreds of monarchs. They fed half of the caterpillars milkweed grown at current CO2 levels. The other half got milkweed grown at nearly double those CO2 levels.
"What we found is that elevated CO2 changes the medicinal quality of the milkweed in a way that makes monarchs sicker. They're less able to tolerate their pathogen, so the parasite becomes more hurtful...to them. And it also reduces their overall lifespan when they're infected in comparison to uninfected monarchs."
The caterpillars that ate milkweed grown with more carbon dioxide grew into butterflies that died as much as a week earlier than the normal life span.
"As a human, you think, oh, well that's not that meaningful. But then as an insect, or as an insect that needs to reproduce within a week, it's pretty important." The study is in the journal Ecology Letters.
Decker say these findings are not just about butterflies and milkweed.
"Many of our medicines come from plants...and so what this study is highlighting to us, or at least creating a red flag for, is the fact that the medicinal contents in those plants could be changing under elevated CO2. They could be going up or down, but it could mean that we lose the medicinal efficacy, the protective ability of that green pharmacy around us."
Thanks for listening for Scientific American — 60-Second Science. I'm Marissa Shieh.
https://m.kekenet.com/broadcast/201903/581312.shtml
Hi, I'm Scientific American podcast editor Steve Mirsky. And here's a short piece from the August 2018 issue of the magazine, in the section called Advances: Dispatches from the Frontiers of Science, Technology and Medicine.
Bloodthirsty by Rachel Nuwer
Mosquitoes are the world's deadliest animals, transmitting diseases that kill hundreds of thousands of people annually. Only the females bite, to acquire protein to make their eggs. But blood can also serve as a refreshing beverage on a hot, dry day.
A new study finds that dehydrated mosquitoes are more aggressive, land more often on hosts and feed more frequently than those with ready access to water. In quenching their thirst, they may also increase the spread of disease. The study is by Joshua Benoit, the biologist at the University of Cincinnati and his colleagues, it appeared in May in Scientific Reports.
Because some mosquitoes lay their eggs on water, researchers have long assumed that wetter conditions lead to more mosquito-borne illness. Yet recent studies have hinted at the opposite, linking increased transmission of diseases such as West Nile fever to droughts. Benoit and his colleagues' discovery helps to resolve these counterintuitive findings.
Benoit became interested in the impact of dehydration on mosquito-feeding behavior by accident: a worker dropped a container of water-deprived mosquitoes and noticed that they dive-bombed him with much greater vigor than usual.
The researchers studied three mosquito species that transmit yellow fever, Zika or West Nile fever. They exposed hundreds of insects to different temperatures and humidity levels in cages with or without access to water and nectar (mosquitoes' preferred sugar source). They then tested how often the pests chose to bite a "host": in this case a warm, waxy plastic membrane coated in artificial sweat and filled with chicken blood.
Within a few hours up to 30 percent of mosquitoes without water fed on their host's blood—compared with 5 to 10 percent of those that had water.
These findings have real-world applications for predicting rates of disease transmission.
That was Bloodthirsty by Rachel Nuwer.
https://m.kekenet.com/broadcast/201904/582483.shtml
This is Scientific American — 60-Second Science. I'm Christopher Intagliata.
Last year, astronomers observed two neutron stars collide—a crash transmitted in gravitational waves to detectors here on Earth. Represented in sound, you can hear a small upwards sweep in frequency, in the data, if you listen closely.
(CLIP: LIGO neutron star merger)
Several seconds later, the first waves of electromagnetic radiation arrived here on Earth — the first time a collision has been detected by both light and gravitational waves. And it's in studying the electromagnetic echoes of the collision that astrophysicists have gotten a far better glimpse of what really happened after those binary neutron stars merged, 130 million light-years away.
"Oh yeah, absolutely, so it gives us an understanding of basically all the nitty gritty of what's going on after the merger takes place." Kunal Mooley, an astrophysicist at Caltech.
First, he says, the stars collided (CLIP: Ligo merger)... creating a massive, black hole–like object, which started sucking up the cloud of neutron-rich cosmic debris left over from the crash. But its appetite was limited.
"It cannot eat all of it, so some bit of it basically escapes." Those escaping leftovers spewed outward into space, as a powerful jet. But along the way, Mooley says, the jet appears to have interacted with that cloud of neutron-rich material, blowing up a sort of cocoon within the debris floating around the collision. Until finally, the jet burst out and slammed into interstellar space... releasing yet more radiation we could detect here on Earth.
The full play by play is in the journal Nature.
In this case, Mooley says, we were lucky to spot the event—the narrow jet was pointed close to Earth. But these collisions could be happening all the time, just that their jets point in directions hard to detect from our planet. But maybe, he says, astronomers can now look for those 'cocoons' as an alternate way to study these colossal bits of cosmic wreckage.
And while gravitational waves are exciting, "there's a lot more to be learned through electromagnetic waves and gravitational waves than that is to be learned through gravitational waves alone." When the LIGO gravitational wave detector fires up, early next year, he says, he'll be watching, waiting, perhaps, for his next study subject.
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.