At the end of the last Ice Age, humans undertook an epic American road trip — trekking from a northern land bridge into interior of North America. But details about the route and timing of that trip are hotly debated.
Some researchers think that humans followed a so-called “ice-free corridor” along the eastern Rocky Mountains. Studies have suggested, though, that the corridor froze over and became impassable around 21,000 years ago. Now, a bread crumb trail of fossils showing the movement of ancient bison indicates that the corridor may have reopened a few thousand years later, researchers report in the Proceedings of the National Academy of Sciences the week of June 6.
Analyzing DNA samples from 78 bison fossils unearthed in Canada, a team led by Beth Shapiro of the University of California, Santa Cruz, found that genetically distinct northern and southern populations moved north and south along the corridor by 13,000 years ago. That means humans may have also hiked along the slopes of the Rockies at the same time.
These probably weren’t the first humans to head south. Recent archaeological evidence points to early Americans trekking as far as Chile more than 15,000 years ago. But the corridor could have served as a later route, the team argues.
Kids are fascinated by fireflies. So are scientists, who, despite decades of research, are still perplexed by many of the mysteries posed by “lightning bugs.” In Silent Sparks, biologist Sara Lewis explores both the cultural and scientific fascination with these marvelous beetles.
Many creatures can manufacture their own glow, Lewis notes, but fireflies are some of the few that can readily turn their lamps on and off. Not all of the world’s nearly 2,000 firefly species light up as adults. But all of their larvae do, which suggests that the bioluminescence may have first evolved in a dinosaur-era ancestor as a “Don’t eat me! I’m toxic!” signal to predators. Only later would adults have co-opted this glimmer for the mating displays that most people are familiar with. Some of the most impressive firefly shows involve the synchronous flashing of thousands of insects. Each mating season, these Christmas tree–like spectacles draw thousands of tourists to locales as diverse as Tennessee and Malaysia. Although researchers have a fairly good idea of how the fireflies synchronize their flashings — in some species, males continually adjust their flashing rate based on their neighbors’ activity — scientists still haven’t figured out why they do so.
Fireflies aren’t just pretty; they’re useful. For instance, food inspectors monitor food contamination by taking advantage of the chemical reactions that the insects use to signal their mates. These reactions occur only in the presence of ATP, an energy-storing chemical found in all living cells, making the glowing substances a keen detector for food-tainting bacteria such as Salmonella or E. coli.
Silent Sparks is at its best when Lewis describes her own experiences in the field, such as lying on her back on the forest floor while flickering fireflies wafted mere inches above her nose. For readers who would like their own experience, Lewis includes a field guide to the most common species found in the southeastern United States (the hot spot of North American firefly diversity).
So grab a copy of the book, along with a net, jar and kid you love, and relive fond childhood memories while inspiring a few new ones.
In the years after the animated movie Finding Nemo was released by Pixar in 2003, sales of clownfish spiked as fans, little and big, rushed to buy their own “Nemo.” So many Nemos were purchased that the sales actually depleted some wild stocks of the fish. Pressure on those wild populations has since dropped, thanks to efforts to increase captive clownfish breeding. But now there are worries that Nemo’s sequel, Finding Dory, may have a similar effect on Dory’s species, the blue tang — and an even bigger impact on the coral ecosystems in which these fish are found.
Despite concerted efforts, scientists have been unable to convince blue tangs to breed in captivity. That means that every blue tang, every Dory, sold has to be captured from the wild. And a surprisingly large number of those fish are captured with cyanide, new research shows.
Most of the 11 million fish sold in the U.S. aquarium trade come from coral reefs in the Indo-Pacific. In some places, like Hawaii and Australia, there are decent rules and enough enforcement of them that fish can be collected without too much harm to ecosystems. But in others, there aren’t enough laws or enforcers to prevent disturbing, destructive practices, such as fishing with explosives or cyanide.
For the aquarium trade, cyanide fishing is “cheap and easy to do,” says Craig Downs, executive director of the Haereticus Environmental Laboratory in Clifford, Va. A diver adds a pellet of cyanide to a bottle and squirts a bit on a target fish. Or they may use larger quantities pumped down from their boat. The poison quickly stuns the fish, which can then be captured and later sold.
But cyanide is deadly. Coral exposed to cyanide bleaches and dies. Other fish and organisms left behind can die. Even the fish that enter the aquarium trade may die within a few weeks or months of being caught. “If you survive [exposure], you’re messed up for the rest of your life,” Downs says. And while there are laws that should prevent divers from employing this fishing method — and from wholesalers in the United States from being able to purchase fish caught this way — “this practice happens all through the Indo-Pacific,” says Downs. As many as 30 million fish may be caught this way every year, and 90 percent of those may die.
There is no way for someone purchasing a fish in a pet store to tell if the animal had been exposed to cyanide. “You have to be a fish pathologist” to see the signs, Downs says. But after a fish, human or other organism is exposed to the toxin, it will excrete a cyanide metabolite, thiocyanate, in its urine. And this can be detected in the water in which a captive fish is living.
Recently, Downs and Rene Umberger, director of the nonprofit organization For the Fishes, wanted to get an idea of how many fish sold in pet stores were caught with cyanide. They purchased 89 fish from shops in California, Hawaii, Maryland, North Carolina and Virginia, collected water samples and sent them off to an independent laboratory. More than half came back positive for cyanide exposure, including many of the blue tangs. None of the fish from companies that breed fish in captivity came back positive, though. The results of this initial study will be presented later this month at the International Coral Reef Symposium in Hawaii.
A 2008 report from NOAA estimated that 90 percent of the aquarium fish imported into the United States were captured with cyanide or other illegal methods. And Downs suspects that cyanide use for the fish in his study may be higher than he and his colleague are now reporting. The fish only excrete detectable levels of thiocyanate for a short time after exposure. Plus, initial runs of a more sensitive method for detecting the chemical show that many of the negatives may really be positives for exposure, he says.
He is hoping that this method might be turned into an easy tool that can be used by consumers, citizen scientists and enforcement agencies to quickly detect fish that have been illegally caught with cyanide, which would hopefully drive down the trade.
This doesn’t mean that all saltwater fish are off limits for consumers, though. “If consumers really want to have coral reef fish, then going the cultured route is the way to go,” Downs says. There aren’t many of those fish — only 42 or so species among the more than 1,800 currently traded in the United States — but identifying them is easy. Umberger’s group has a free iOS app, Tank Watch, that lists them all. And even though the app doesn’t list every species that may be in a store, if a species isn’t on their good list, it can be assumed to be bad.
So go ahead and buy Nemo, if you must, but leave Dory and most of her fishy cousins where they belong — in the ocean.
BOSTON — New studies find a rise in drug-resistant urinary tract infections in pets, raising concerns that companion animals may serve as microbe reservoirs that could contribute to the spread of potential superbugs. About four in 10 U.S. households own dogs, which sleep with us, eat off our plates, lick our faces and leave plenty of poop to scoop. Cat ownership is nearly as prevalent.
It’s not clear whether pets are picking up the resistant microbes from their owners, or vice versa, said Cátia Marques, a veterinary medicine doctoral candidate. She presented the research, conducted by scientists from the University of Lisbon in Portugal, June 20 at a joint meeting of the American Society for Microbiology and the Interscience Conference on Antimicrobial Agents and Chemotherapy. More research is needed to answer that question, she said. Either way, scientists worry that companion animals provide another haven for bacteria to mingle and pick up genes that give them resistance to drugs, said Michael Schmidt of the Medical University of South Carolina in Charleston, who was not involved in the new work. “It is a substantial issue,” he said.
Other research has examined human-pet sharing of bacteria, but the subject has been little explored for urinary tract infections, which are extremely common. The new research found a growing resistance in veterinary infections to antibiotics critical for treating human illness. In one study, samples of the bacterium Proteus mirabilis taken over 16 years in Portugal showed a steady climb in the prevalence of resistant strains. An example: Resistance to a class of drugs known as third-generation cephalosporins grew from 2 percent of samples in 2004 to 20 percent today. Other research found worrisome multidrug resistance in infections caused by Klebsiella. In a third study, which tested for resistance in urinary tract infections in pets across Europe, patterns of drug resistance in dogs and cats tracked that of humans, the researchers found.
In humans, doctors have watched warily as resistance to urinary tract infections has grown. In May, scientists reported the discovery of a woman with a urinary infection resistant to colistin, a rarely used drug of last resort (SN Online: 5/27/16). It’s not clear how the patient contracted the resistance, but given colistin’s role as a last-ditch drug, it raised the specter of an unstoppable microbe.
While the new research is broader, it isn’t the first study to raise concerns about the role of companion animals in difficult-to-treat urinary infections. In 2013, German researchers writing in the Journal of Antimicrobial Therapy described finding carbapenem-resistant Escherichia coli and Klebsiella urinary infections in six dogs — a discovery later called a phenomenon “of great concern” in a commentary in the same journal. E. coli and P. mirabilis are the two biggest causes of urinary tract infections. Carbapenem, which the researchers in Portugal did not test for, is also considered a drug of last resort for urinary infections.
Whether humans are giving resistant organisms to their animals or vice versa, the findings emphasize that the battle against resistance needs a global strategy that involves veterinarians along with human doctors and patients, Marques said. “We need to have a common public health approach,” she said.
Schmidt also cautioned that people who are particularly vulnerable to urinary infections, such as pregnant women, take extra care around their pets, especially when cleaning up after them. “If you do have a companion animal and you’re prone to these infections,” he said, “be very strict with your hand hygiene before you eat.”
