Tag Archives: hibernation

#FossilFriday: This 250-million-year-old animal could enter hibernation-like states

Illustration of Lystrosaurus in a state of torpor. Credit: Crystal Shin.

Many creatures on Earth today hibernate, essentially entering a state of low metabolism that allows them to go through months at a time without food. According to researchers, this adaptation may be at least 250 million years old, judging from the fossils of a recently described creature that could enter a hibernation-like state.

The fossils of the mammal-like creature, which belongs to the genus Lystrosaurus, were retrieved from Antarctica. Although during Lustrosaurus’ days Antarctica may have been much more welcoming, it would have still experienced extended periods without sunlight each winter.

“Animals that live at or near the poles have always had to cope with the more extreme environments present there,” said lead author Megan Whitney, a postdoctoral researcher at Harvard University who conducted this study as a University of Washington doctoral student in biology. “These preliminary findings indicate that entering into a hibernation-like state is not a relatively new type of adaptation. It is an ancient one.”

The stout, four-legged forager was roughly pig-sized, although some could grow up to 8 feet long (2.5 meters). Lystrosaurus, which has been found in India, China, Russia, Africa, and now Antarctica, had no teeth at all. Instead, the stubby vertebrate had a pair of tusks in the upper jaw, which likely served to penetrate ground vegetation and dig out roots and tubers.

Like elephants, these tusks grew continuously throughout Lystrosaurus‘s life. In their new study, Whitney and colleagues used cross-sections of fossilized tusks to infer valuable information about the metabolism, growth, and stresses of during these creatures’ lifetimes. They did so for many specimens, comparing cross-sections of tusks from six Antarctic Lystrosaurus to cross-sections of four Lystrosaurus from South Africa.

During Lystrosaurus‘ heyday in the Triassic, South Africa and Antarctica were joined together in a supercontinent called Pangea. Back then, Antarctica was about 72 degrees south latitude (still well within the Antarctic circle) while South Africa was displaced by more than 550 miles north compared to its position today, sitting at a warm 58-61 degrees south latitude.

This thin-section of the fossilized tusk from an Antarctic Lystrosaurus shows layers of dentine deposited in rings of growth. Credit: Megan Whitney/Christian Sidor

Similar to how a tree’s rings can tell how many years it was alive for, or when it suffered drought, layers of dentine were also deposited in concentric circles in the fossilized tusks. Curiously, Antarctic tusks had thicker, more closely spaced dentin rings, indicating periods of less deposition. For the researchers, this suggests periods of prolonged stress that resemble the effects of hibernation.

“The closest analog we can find to the ‘stress marks’ that we observed in Antarctic Lystrosaurus tusks are stress marks in teeth associated with hibernation in certain modern animals,” said Whitney.

That’s not to say that the researchers can definitely conclude that Lystrosaurus could hibernate, which is essentially a resting state of deep sleep, during which the body’s metabolic rate and temperature drop considerably. For instance, during hibernation, the gopher’s body temperature will drop from its normal 37 degrees Celsius to almost 0 degrees Celsius. The heartbeat also becomes slow and irregular, alongside a slowing breathing rate.

A map of Pangea during the Early Triassic, showing the locations of the Antarctic (blue) and South African (orange) Lystrosaurus populations compared in this study. Credit: Megan Whitney/Christian Sidor.

The same stress may have been caused by another hibernation-like form of torpor, which involves a more short-term reduction in metabolism, the researchers wrote in the journal Communications Biology.

In any event, Lystrosaurus must have benefited greatly from hibernation-like states. Although Antarctica was much warmer than it is today and might have even been forested during the Triassic, it would have still experienced extreme annual variations of daylights, with the sun absent for months at a time during winter. Torpor may have helped creatures such as Lystrosaurus cope with the dire strains of pitch-black winter.

“To see the specific signs of stress and strain brought on by hibernation, you need to look at something that can fossilize and was growing continuously during the animal’s life,” said co-author Christian Sidor, a University of Washington professor of biology and curator of vertebrate paleontology at the Burke Museum. “Many animals don’t have that, but luckily Lystrosaurus did.”

If the findings are confirmed, this means  Lystrosaurus is the earliest example of a hibernating vertebrate that we know of. It would also highlight the fact that many different features of modern animals likely existed hundreds of millions of years ago, long before any humans were around to study them.

“Cold-blooded animals often shut down their metabolism entirely during a tough season, but many endothermic or ‘warm-blooded’ animals that hibernate frequently reactivate their metabolism during the hibernation period,” said Whitney. “What we observed in the Antarctic Lystrosaurus tusks fits a pattern of small metabolic ‘reactivation events’ during a period of stress, which is most similar to what we see in warm-blooded hibernators today.”

E.coli rendering.

Some bacteria can ‘hibernate’ through antibiotic treatments, new paper finds

When antibiotics come knocking, bacteria may simply sleep the threat away.

E.coli rendering.

Digital rendering of E.coli bacteria.
Image via Fotolia.

Researchers from the University of Copenhagen report that pathogenic bacteria have a surprising defensive tactic against antibiotics: hibernation. The research might help us fight antibiotic-resistant infections.

Nap it out

Almost all types of pathogenic bacteria eventually develop strains that are tolerant of or resistant to antibiotic treatments. This is particularly problematic as the fraction of bacteria which survive treatment — although tiny — can later multiply, maintaining infection in the face of our antibiotic efforts.

However, a small number of bacterial species do away with this mechanism completely, yet still retain the ability to resist the drugs meant to kill them. In an effort to understand why, the Copenhagen team turned to E. coli.

“We studied E. coli bacteria from urinary tract infections that had been treated with antibiotics and were supposedly under control,” says Professor Kenn Gerdes of the University of Copenhagen’s Department of Biology, paper co-author.

“In time, the bacteria re-awoke and began to spread once again,” he explains

The team found that a few individuals in the overall bacterial population ‘hid’ from the antibiotics in a dormant, hibernation-like state. The bugs slept through the treatment, and only resumed their regular activity once the dangerous compounds were removed.

Antibiotics generally work by attacking a bacteria cell’s ability to grow — so these hibernating individuals are virtually immune to their effects.

“A bacterium in hibernation is not resistant. It is temporarily tolerant because it stops growing, which allows it to survive the effects of an antibiotic,” says Professor Gerdes.

Hibernating bacteria seem to share the same genetic characteristics as all other individuals in a given population, the team reports. So, as of right now, they can’t say exactly why some members enter a dormant state while their peers do not. The team did, however, identify an enzyme in dormant individuals that governs the ‘hibernation’ process. A compound that could interfere with this enzyme’s functioning, or its synthesis, could help to keep these bacteria from becoming invulnerable to antibiotics.

“The discovery of this enzyme is a good foundation for the future development of a substance capable of combating dormant bacteria cells,” says Professor Gerdes.

“The enzyme triggers a ‘survival program’ that almost all disease-causing bacteria deploy to survive in the wild and resist antibiotics in the body. Developing an antibiotic that targets this general programme would be a major advance,” he adds.

Although the findings are encouraging, it will still be several years before they can be turned into a safe and useable treatment, the team writes.

The paper “The kinases HipA and HipA7 phosphorylate different substrate pools in Escherichia coli to promote multidrug tolerance” has been published in the journal Science Signaling.

Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. Credit: Art by Mauricio Antón.

Scientists find primitive 3.5-million-year old bear with a sweet tooth for berries

Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. Credit: Art by Mauricio Antón.

Reconstruction of the mid-Pliocene Protarctos abstrusus in the Beaver Pond site area during the late summer. Credit: Art by Mauricio Antón.

Two 3.5-million-year-old bears had a sweet tooth for berries. Paleontologists have discovered ancient teeth with cavities that serve as evidence.

“This is evidence of the most northerly record for primitive bears, and provides an idea of what the ancestor of modern bears may have looked like,” says Dr. Xiaoming Wang, lead author of the study and Head of Vertebrate Paleontology at the Natural History Museum of Los Angeles County (NHMLA).

“Just as interesting is the presence of dental caries, showing that oral infections have a long evolutionary history in the animals, which can tell us about their sugary diet, presumably from berries. This is the first and earliest documented occurrence of high-calorie diet in basal bears, likely related to fat storage in preparation for the harsh Arctic winters.”

A rare glimpse into High Arctic life

The international team of researchers excavated the ancient bear fossils belonging to Protarctos abstrusus at the Beaver Pond site on Ellesmere Island, Canada. This site is one of the few where fossils have been found in the Arctic, especially mammal fossils.

Unlike other sites down south where scientists can chisel fossils out of rock, at Beaver Pond you have to pick your way through layers of peat. The bones are usually fragmented from all the repeated cycles of freezing and thawing, and appear brown or iridescent blue in color due to the presence of a mineral called vivianite.

The first pieces of a bears skulls’ were found in the 1990s. During excavations over the last 14 years, paleontologists have recovered more fragments of the skull, a jaw, and other skeleton fragments. When the researchers pieced together the fragments, they found the pieces belonged to two bears. One was five to seven years old and the other was older. Both didn’t seem to brush their teeth, judging from the cavities.

“It is a significant find, in part because all other ancient fossil ursine bears, and even some modern bear species like the sloth bear and sun bear, are associated with lower-latitude, milder habitats,” says co-author Dr. Natalia Rybczynski, a Research Associate and paleontologist with the Canadian Museum of Nature. “So, the Ellesmere bear is important because it suggests that the capacity to exploit the harshest, most northern forests on the planet is not an innovation of modern grizzlies and black bears, but may have characterized the ursine lineage from its beginning.”

Digital reconstruction of the Canadian Arctic fossil bear, Protarctos abstrusus. Credit: Xiaoming Wang.

Digital reconstruction of the Canadian Arctic fossil bear, Protarctos abstrusus. Credit: Xiaoming Wang.

 

Along with the fossils, scientists have found remains of raspberry, blueberry, lingonberry and crowberry plants. Their sweet berries likely helped the ancient bears hibernate through the polar winter, just like their modern cousins.

While Canada’s High Arctic doesn’t look all that hospitable nowadays, three and a half million years ago Beaver Pond was home to a boreal forest. It provided a home to a variety of animals like beavers, deer, and three-toed horses, to name a few.

A view of the Beaver Pond fossil site, with a number of the animals and plants based on fossils recovered from the site. Credit: George "Rinaldinho" Teichmann.

A view of the Beaver Pond fossil site, with a number of the animals and plants based on fossils recovered from the site. Credit: George “Rinaldinho” Teichmann.

In addition to being able to discern what some ancient bears had for breakfast — which is fascinating in its own right — scientists say the fossils also provide a missing link between primitive and modern bears. The findings suggest that bears were stuffing up on a high-sugar diet to hibernate very early in their evolutionary history. About 44 percent of modern black bears have cavities, which are very rare in other animals.

Protarctos abstrusus — a species first discovered in Idaho in 1970 — was able to reach up to 100 kilograms, making it a bit smaller than modern black bears. The two species are related but Protarctos abstrusus is not the direct ancestor of the black bear, which crossed into North America from Asia much later, during the last ice age.

Scientific reference: Xiaoming Wang et al, A basal ursine bear (Protarctos abstrusus) from the Pliocene High Arctic reveals Eurasian affinities and a diet rich in fermentable sugars, Scientific Reports (2017). DOI: 10.1038/s41598-017-17657-8.