News and notes about science
GENES COLOR A BUTTERFLY’S WINGS. NOW SCIENTISTS WANT TO DO IT THEMSELVES
Only nature can paint the gorgeous colors and patterns on a butterfly’s wings. But scientists now say they have mastered the first steps and hope in time to control the entire coloring system, making it possible to design living butterfly wings.
The patterning and colors on butterflies’ wings are governed by suites of genes. The new CRISPR-Cas gene-editing technique now makes it much easier to figure out what a gene does by deleting it and seeing what happens.
Two teams of biologists report in The Proceedings of the National Academy of Sciences that they have used the technique to explore the roles of two master genes that control the appearance of a butterfly’s wings.
A group led by Linlin Zhang and Robert D. Reed of Cornell University has found that a gene called optix has a remarkable role: It controls all the color in a butterfly’s wing. When optix is deleted from the Gulf fritillary’s eggs, the resulting adult butterflies wear a ghostly black and silver livery.
That’s because in the absence of the optix gene, the butterfly’s scales produce melanin, a black pigment, instead of the usual chestnut coloring.
The biologists had already suspected that optix played a role in activating the butterfly’s brown pigment. But they were surprised that the black pigment was turned on in the absence of optix.
A second group, led by Anyi Mazo-Vargas of Cornell University and Arnaud Martin of George Washington University, has explored the role of a gene called WntA.
The standard pattern of nymphalid butterflies consists of four bands, parallel to the body, that run between it and the edge of the wings. The second band, called the central symmetry system, contains the pattern in the middle of the wings, and the third band holds the eye spots. Martin’s team found that when they delete the WntA gene with the CRISPR technique, the central symmetry system band disappears entirely from the wings of the speckled wood and buckeye butterflies. But in other species, the loss of WntA has very different effects, suggesting that the gene has been adapted many times to play different patterning roles as new butterfly species evolved. Nicholas Wade
THE SNOW LEOPARD IS NO LONGER ENDANGERED. BUT IT’S STILL AT RISK
The snow leopard is no longer an endangered species, but its population in the wild is still at risk because of poaching and habitat loss, conservationists said this month.
The International Union for Conservation of Nature said new data taken through 2016 prompted the reclassification of the snow leopard from the endangered list to the vulnerable category. The difference means that the animals have gone from “very high risk” to “high risk” of extinction in the wild. The global population of the snow leopard is estimated at 2,500 to 10,000 mature animals.
But the leopard could still face a population decline of 10 percent or more over the next three generations in its habitats, which are mostly mountainous areas of Central Asia, including Kyrgyzstan and Pakistan. It “still faces a high risk of extinction,” the conservation group said, from habitat loss and degradation, declines in prey populations, and poaching for illegal wildlife trade, among other reasons.
“It is essential to continue and expand conservation efforts to reverse its declining trend and prevent this iconic cat from moving even closer to extinction,” the group said.
Emerging potential threats include mining and other infrastructure development that would affect their habitats.
Snow leopards range across 12 countries in Central Asia in remote and rugged terrain. Christine Hauser
AFTER THE HURRICANE, A FINAL RESTING PLACE
After Hurricanes Harvey and Irma battered Texas, the Caribbean and Florida, many unexpected mementos were left behind.
Some were surprising, like the old — and possibly historically significant — wooden canoe that washed ashore not far from Cape Canaveral, Fla. Some were macabre, like the dozens of coffins that were nudged above ground in Texas. And some, like the many animals wrenched from their habitats or left stranded by receding tides, were alive.
A creature that washed up in Harvey’s wake on the shores of Galveston Bay in Texas City drew attention.
Preeti Desai, a social media manager at the National Audubon Society, was documenting the organization’s efforts to assess the hurricane’s effect on birds in the area on Sept. 6 when she came across a baffling animal.
It was dead, brown, bloated and fanged.
Several experts suggested the creature could be a fangtooth snake-eel, a fish native to the area that tends to hide in underwater burrows but darts out to snatch fish and crustaceans. Desai esti-
mated that it was 3 or 4 feet long, including its tail. Jacey Fortin
ONE NIGHT A YEAR, THIS CACTUS FLOWER MAY SURPRISE YOU
Tom Randall was walking home late on a recent evening when, against his better judgment, he obliged a disembodied voice from behind a hedge asking if he wanted to see a beautiful flower.
It turned out to be a nightblooming cereus, a blanket term for around a dozen species of cactuses that produce flowers that only bloom at night. This flower (possibly the species Epiphyllum oxypetalum), according to Randall’s account, blooms one night a year.
The fragrant blossom — in his words, the size of “a newborn baby’s head” — graces the night for only a few hours. By morning, like a sylvan Cinderella, its white petals wilt before the sun ever gets a shot at a kiss.
Hosting parties and gatherings to celebrate the debut of these unlikely belles of darkness is a long-held tradition. In 1937, for example, a Rhode Island newspaper described a crowd that gathered one evening at the estate of a wealthy family known for their elaborate parties.
The night-blooming cereus is native to the deserts and subtropics of the Southwest United States, the Antilles and Central and South America. The plants vary in form from species to species; without blooms, some look like gnarled nests of bare sticks or green, flatleaved cactus-orchid hybrids.
Some grow in the ground, and others in trees, like air plants. One plant, depending on its size, may have dozens of blossoms — and they typically bloom en masse.
The blooms are summoned not by magic, but temperature, humidity or rainfall, with most species blooming at rainy times in the summer. Most appear to follow a lunar cycle, with more buds emerging on or around a full moon. Joanna Klein
HOW THREE FRIENDS PROVED THAT JELLYFISH CAN SLEEP
Worms and fish do it. Birds and bees do it. But do jellyfish fall asleep?
Answering the question required a multistep investigation by a trio of California Institute of Technology graduate students. Their answer, published Sept. 21 in Current Biology, is that at least one group of jellyfish called Cassiopea, or the upside-down jellyfish, does snooze.
The finding is the first documented example of sleep in an animal with a diffuse nerve net, a system of neurons that are spread throughout an organism and not organized around a brain. It challenges the common notion that sleep requires a brain. It also suggests sleep could be an ancient behavior because the group that includes jellyfish branched off from the last common ancestor of most living animals early on in evolution.
To prove that jellyfish sleep, the students had to demonstrate that they fulfill three behavioral criteria. First, the animals must undergo a period of diminished activity, but they must also be able to be aroused from this state, to distinguish sleep from other states, such as comas. Over six days and nights, researchers monitored 23 jellyfish, which pulsed about 30 percent less at night than during the day. If fed or poked in the middle of the night, the jellyfish would temporarily stir.
Next, the animals must exhibit decreased responsiveness to stimuli while sleeping. Upsidedown jellyfish get their name from the fact that they sit upside-down on the seafloor — they don’t like to be suspended in water. To test their responsiveness, scientists placed the jellyfish in little cubbies with removable bottoms that were elevated within the tank. When the researchers pulled the cubby bottoms out during the day, the creatures would immediately swim to the bottom of the tank. At night, however, they would sluggishly float around at first.
Last, the animals must show an increased need for sleep if they are kept from it, so biologists pulsed water through the jellyfish’s tank every 20 minutes at night to prevent the creatures from sleeping continuously. The following day and night, the jellyfish exhibited much lower levels of activity than normal, suggesting sleep deprivation. Steph Yin
HIS STUDY ON EELS? YES, IT WAS SHOCKING
Kenneth C. Catania, a biologist at Vanderbilt University, wanted to get a sense of just how big a jolt an electric eel can deliver. For a study published this month in Current Biology, he allowed one to attack his own arm.
In his earlier experiments, he found that an electric eel is like a battery. When confronted with prey or a threat, it transforms into a Taser-like shocking apparatus. To make catching its dinner easier, it sends electric pulses through the water that, in succession, can paralyze its prey, or in just a few pulses, can cause it to flail around in the water, revealing its location through waves the eel senses with hairs on its body.
When large, threatening animals get too close for comfort, eels can wrap around the intruder or leap up to create a direct electric circuit. But what was that circuit like? In the latest study, Catania solved each variable of the circuit with traditional tools for measuring electricity. But working out the final variable — the resistance of a human arm — required a more creative, daring, approach.
When the eel leapt out of a tank of water and rested its head on Catania’s arm, electricity flowed from the head, to his arm, to the water and back to the eel’s tail to complete the circuit. To measure this flow he stuck his hand in a plastic container with exposed metallic tape on the inside and outside connected to a wire. The same electricity that flowed through his arm would also flow through the wire — and that he could measure.
When the eel leapt to his arm, he withdrew it immediately, comparing it to how you respond if you accidentally put your hand on a hot stove or touch an electric fence.
Catania experienced about 10 shocks like this during the experiment, but with the data he obtained, he was able to use his numbers to extrapolate what kind of shocks eels of any size could deliver. A large eel, he said, could paralyze you, causing you to fall down and potentially drown. Joanna Klein