Centenarian Tortoises May Set
the Standard for Anti-Aging
For mammals like humans, aging is inevitable. No matter how many vitamins we take, skin sags, bones soften and joints stiffen over time. However, turtles and tortoises age more gracefully. Despite their wrinkled skin and toothless gums, species like Galápagos giant tortoises seem unscathed by the ravages of aging. Some show few signs of slowing down as they plod into their 100s.
To determine what drives these ageless wonders, two groups of researchers examined turtles, tortoises and their ectothermic, or coldblooded, brethren in a pair of studies published recently in the journal Science. Prior aging research has largely revolved around warm-blooded animals like mammals and birds. But ectotherms like fish, reptiles and amphibians dominate the longevity record books.
In one of the new studies, researchers compiled data sets on 77 species of wild reptiles and amphibians. The team utilized decades of monitoring data to analyze traits like metabolism to determine their impact on aging and longevity.
"We had these awesome data sets to get at questions of aging in a way that hasn't been done before," said Beth Reinke, an evolutionary biologist at Northeastern Illinois University and an author of the new study.
Living so long requires a gentle aging curve. After most animals reach sexual maturity, much of their energy is devoted to reproduction at the expense of mending aging tissue. This physical deterioration, or senescence, often causes an uptick in mortality risk as older animals become susceptible to predators or disease. But several coldblooded animals experience little senescence as they age.
One theory is that coldblooded animals are better equipped to manage the wear of aging because they rely on the environment to calibrate their body temperatures instead of the energy-draining metabolisms of endothermic, or warm-blooded animals. But Reinke and her colleagues discovered that some ectotherms aged much faster than similar-sized endotherms, while others aged much slower. The only group that barely aged were turtles and tortoises.
The other study drilled deeper into the aging of turtles. The researchers examined age-related decline in 52 species of captive turtles and tortoises in zoos and aquariums. They found that 75% of the species exhibited low or negligible senescence.
Turtles being the anti-aging standard makes sense, considering their sluggish metabolisms. Researchers have also linked their sturdy shells to longer lives.
While these lumbering reptiles cannot outpace death, they may hold insights for prolonging longevity and decreasing age-related decline.
-- Jack Tamisiea
Earth's Largest Rodents Were Smaller Than We Once Thought
Modern rodents range in size from pygmy mice weighing less than 1 ounce to stocky capybaras pushing 175 pounds. But even the largest capybara is a pipsqueak compared with some prehistoric rodents that resembled a cross between a supersized capybara and a hairy hippopotamus. Paleontologists estimate that one, Phoberomys pattersoni, may have weighed as much as 1,300 pounds. Another, Josephoartigasia monesi, was believed to be around 2,000 pounds, as big as a bison.
But these size predictions have long sparked debate. "People have said they're the size of bison, but no one had any methods that could confidently nail down these sizes," said Russell Engelman, a paleontologist pursuing his doctorate from Case Western Reserve University.
So Engelman proposed a new method for accurately describing the dimensions of these rodents of unusual size. In a study published recently in the journal Royal Society Open Science, he downsized the animals by comparing a joint at the back of the skulls of Phoberomys, Josephoartigasia and other prehistoric rodents with those in large modern mammals instead of their pint-size relatives.
Between 2 million and 8 million years ago, giant rodents like Phoberomys and Josephoartigasia inhabited South America's wetlands.
Accurately sizing these gargantuan rodents has proved difficult. One reason is a lack of fossils. While paleontologists have unearthed leg bones and other bits of Phoberomys's skeleton, Josephoartigasia is known from only a single skull. Without fossil evidence, researchers often rely on the anatomies of an extinct animal's closest living relatives. However, traits like Josephoartigasia's prolonged skull and Phoberomys's bulky femurs are not found in living rodents. Thus, simply increasing the size of a capybara fails to render accurate anatomical estimates.
So Engelman turned to the occipital condyle, the joint that helps connect an animal's skull with its spine. The size of this joint varies little across all mammals to ensure the skull and spine stay securely attached, making it a bellwether for comparing different species.
Recently, Engelman measured the width of the joint in more than 400 species of mammals, including mice and African elephants. He concluded that Phoberomys maxed out at under 450 pounds, and Josephoartigasia at around 1,000 pounds.
The new findings are less eye-popping than earlier estimates. But Virginie Millien, a zoologist at McGill University who studies the body sizes of rodents, said 1,000 pounds is "still a really big rat."
-- Jack Tamisiea
Remember Pizza Rat?
Meet Pollinator Rat
Birds do it. So do bees. Especially bees.
But common rats pollinating plants? In a study published in June in the journal Ecology, two researchers report that in Colombia, brown rats, the same ones that feast on garbage and steal slices of pizza in cities around the world, may be the primary pollinator in urban settings for the feijoa plant, which produces a fruit that is widely consumed in the country.
"I was very surprised because, in the beginning, I knew about the stories but never paid much attention," said Carlos Matallana-Puerto, a plant biologist at the State University of Campinas in Brazil. "Then when I started to study, I started to get excited because I started to realize that the thing makes sense."
In Matallana-Puerto's hometown Duitama, Colombia, residents had long reported seeing typically nocturnal rats walking and perching in trees in broad daylight.
But when he started studying the science of pollination in college, the stories took on a new meaning: Could the rats have been pollinating the trees?
It was not a leap to wonder if rats could be pollinators. An estimated 343 species of mammals are pollinators. Bats are well-known for pollinating bananas, avocados, mangoes, agave and durian. Elephant shrews, honey possums, lemurs and other rodents have also been spotted helping plants do their reproductive deeds.
To test his hypothesis, Matallana-Puerto did what any good naturalist would do: He watched and observed that the rats were attracted to feijoa plants. They produce a sweet fruit that tastes like a mix of pineapple and guava.
From his bedroom window, Matallana-Puerto saw that the brown rat accounted for 88% of all animal visits to feijoa flowers. Birds visited just a handful of times during his 60 hours of observation.
Importantly, the rats do not appear to damage the reproductive parts of the flowers when they feast on the fleshy white petals. Instead, the rodents brush against the scores of scarlet stamens, which carry the pollen that could then cling to their fur coats until being transferred to another feijoa tree.
"It's very unusual for a plant to have petals as the resource, and it's pretty amazing that the rats figured out that they're nutritious," said Jeremy Midgley, an emeritus professor of biology at the University of Cape Town in South Africa.
-- Richard Sima
A Giant Stingray May Be the World's Largest Freshwater Fish
For 17 years, Zeb Hogan, a biologist, has been searching for the world's largest freshwater fish. On June 13, his team found it -- a giant freshwater stingray, or Urogymnus polylepis.
The ray, hauled out of the murky waters of the Mekong River in Cambodia, measured 13 feet in length before it was returned to the river. And at 661 pounds, it was 15 pounds heavier than a Mekong giant catfish caught in Thailand in 2005. Hogan said he had previously established that freshwater fish as the largest ever caught.
While this species of giant stingray has an extremely dangerous venomous barb that can reach nearly 1 foot in length, they are not usually a threat to humans. More often, they wind up in the market as a source of cheap protein.
Fishers in Cambodia first alerted Hogan and his team at Wonders of the Mekong Project, which works to protect the Southeast Asian river's aquatic diversity and is sponsored by the U.S. Agency for International Development, that they had caught a stingray larger than anyone had ever seen. Team members rushed to the small river island, called Koh Preah, and lined up three industrial scales. Using a tarp, they hoisted the stingray out of the water and onto the scales to verify its weight.
The discovery comes less than a month after another giant stingray -- that one weighing 400 pounds -- was caught and released nearby. Two other enormous rays have also been caught this year.
"The fact that the world's largest freshwater fish was caught in the Mekong is remarkable," Hogan said. "This is a heavily populated region, and the river faces a ton of challenges, including lots of fishing."
With so many giant stingrays caught in recent months and all of them female, Hogan believes this stretch of the river and the deep pools it contains are a critical breeding ground for the species. The area is also home to freshwater dolphins, giant soft-shell turtles, giant catfish and giant barb, which is in the carp family.
"So it's a very unique place, and very understudied," he said.
While breaking the world record was not scientifically important, Hogan said that the existence of this fish is an indicator for the health of its ecosystem. He also hoped the discovery reminds the local community how special this river is, and how much it's in need of saving.
-- Jason Bittel
This article originally appeared in The New York Times.