NEWS AND NOTES ABOUT SCIENCE
A FISH IMPATIENT FOR MOTHERHOOD
Killifish are a family of freshwater fish that have evolved to survive in the most difficult of situations. In the United States, for instance, the Atlantic killifish is known for having adapted to live in heavily polluted places such as the Lower Passaic River in New Jersey.
But in small murky puddles that come after heavy rains in parts of East Africa, another killifish, called Nothobranchius furzeri, or the African annual fish, has developed its own unique adaptations to its environment. Its embryos are able to enter a state of diapause, similar to hibernation in bears, when conditions aren’t right.
It turns out that entering dormancy isn’t the only thing that’s unusual about this African killifish. In a paper published recently in Current Biology, a team of Czech researchers report that N. furzeri has the quickest known rate of sexual maturity of any vertebrate — approximately two weeks. By studying the fish’s unusual life cycle, they hope to gain insights into the process of aging in other vertebrates, including humans.
Martin Reichard, a biologist who is studying the evolution of aging at the Czech Academy of Sciences’ Institute of Vertebrate Biology, led a team of colleagues to Mozambique to study the fish’s developmental stages in the wild. There, they were able to observe embryos buried in the sand that had entered a dormant state. They also documented their maturation after rainfall.
When N. furzeri receive cues from their environment, they can be flexible in sexual development. Under these circumstances, their embryos enter a stage of dormancy called embryonic diapause, a reproductive strategy that extends their gestational period and helps them survive unfavorable conditions, such as a dry season.
But when it rains, they undergo rapid growth, going from juvenile fish to mature adults that are able to reproduce in about two weeks.
That ability comes at the expense of the fish’s life span. They have an earlier onset of aging than other vertebrates.
“The fish display comparable cellular deterioration and changes found in aging humans after several decades,” Reichard said.
With this information, researchers found that the fish’s life cycle depends on the environment in which the embryo is laid. Bilal Choudhry
NOW, THERE MAY BE HOPE FOR HEMOPHILIA
Scientists are edging closer to defeating a longtime enemy of human health: hemophilia, the inability to form blood clots.
After trying for decades to develop a gene therapy to treat this disease, researchers are starting to succeed. In recent experiments, brief intravenous infusions of powerful new treatments have rid patients — for now, at least — of a condition that has shadowed them all their lives.
There have been setbacks — years of failed clinical trials and dashed hopes. Just this past week, a biotech company reported that gene therapy mostly stopped working in two of 12 patients in one trial.
But the general trajectory has been forward, and new treatments are expected by many experts to be approved in a few years.
No one is saying yet that hemophilia will be cured. Gene therapy — which uses a virus to deliver a new gene to cells — can only be used once. If it stops working, the patients lose the benefits.
There are 20,000 hemophilia patients in the United States who lack one of two proteins needed for blood to clot. It’s a genetic condition, and the gene for blood clotting sits on the X chromosome. Virtually all people with hemophilia are men.
At first, hemophilia seemed ideal for gene therapy.
Then scientists stumbled upon an unexpected bonanza. They found a man in Padua, Italy, who had a genetic mutation that made cells churn out as much as 12 times the usual amounts of factor IX.
Investigators realized that they could put the mutated gene into a virus and use it to insert the mutated gene into the cells of patients with hemophilia B.
The advantage was that they would not have to use so much virus — and the lower the dose, the less likely the immune system would attack.
But hemophilia A has been more daunting.
The viruses used to carry modified genes into patient cells are called adeno-associated viruses. They cannot carry a large gene, and the gene for factor VIII, needed to treat hemophilia A, is enormous.
After 15 years of effort, investigators finally discovered they could reduce the gene to a manageable size by slicing out portions that turned out not to be needed. Gina Kolata
SOMETHING DIGS INTRICATE TUNNELS IN SOME PRECIOUS GEMS. IT MAY BE ALIVE.
Deep red garnets are found all over the world, from Thailand and Sri Lanka to the Adirondacks. They’re even the state gem of New York.
The stones that make their way into rings and necklaces must have a flawless interior. But sometimes garnets are marred with intricate traceries of microscopic tunnels. When Magnus Ivarsson, a geobiologist at the Swedish Museum of Natural History, first saw these tunnels, he wondered what could be making them.
After Ivarsson and his colleagues traveled to Thailand, they found that an assortment of evidence contradicted standard geological explanations for how the cavities might be formed. In a paper in PLOS One, the researchers are floating a new hypothesis: Perhaps what’s making the tunnels is alive.
The researchers looked for alternative explanations. One of the most promising was that grains of another stone wore their way through the garnet. However, the mineral doing the tunneling must be harder than the surrounding substance, and garnets happen to be very, very hard. About the only things that could do that to garnet are diamonds or sapphires. But those aren’t present in significant quantities where these garnets were found, said Ivarsson.
Furthermore, the tunnels branch and connect with one another in a very unusual pattern, looking a bit like the structures made by some kinds of singlecelled fungus colonies. When the researchers cracked the garnets open, they tested the insides of the tunnels and found signs of fatty acids and other lipids, potential indicators of life.
It’s not unheard-of for microorganisms to live in rocks — endoliths, as such creatures are called, have been found living encased within sandstone in the Dry Valleys of Antarctica, among other
places.
At the moment, the researchers’ best guess for the origins of the tunnels goes like this: At first, normal wear-and-tear on the surface of a garnet creates divots. Microorganisms, probably fungi, can colonize these hollows. Then, if the stone is the best nearby source for certain nutrients, such as iron, perhaps they use an as-yet mysterious chemical reaction to burrow deeper, harvesting sustenance as they go.
“I think there’s a two-step process, a superficial weathering, then an organism takes over,” Ivarsson said. Veronique Greenwood
FOSSILS ON AN AUSTRALIAN BEACH REVEAL A SHARKEAT-SHARK WORLD
In 2015 Philip Mullaly was strolling along a beach in Victoria, Australia, when he spotted what looked like a shining serrated blade stuck in a boulder. Using his car keys, Mullaly carefully pried from the rock a shark tooth about the size of his palm.
He did not know it at the time, but the tooth he uncovered once belonged in the mouth of a 25million-year-old giant shark that was twice the size of a great white.
“It was an awesome creature, it would have been terrifying to come across,” Mullaly said.
Mullaly, who is a schoolteacher and amateur fossil hunter, returned to the boulder a few weeks later and to his surprise dug up several more 3-inch teeth.
“It dawned on me when I found the second, third and fourth tooth that this was a really big deal,” Mullaly said.
He contacted Erich Fitzgerald, a paleontologist at the Museums Victoria in Melbourne. Fitzgerald identified the teeth as belonging to a type of megatoothed shark called the great jagged narrow toothed-shark, or Carcharocles angustidens.
“Angustidens was a bloody big shark, we’re talking more than 30 feet long,” Fitzgerald said.
Fitzgerald also determined that all of the teeth most likely came from the same individual shark. Though people have found single shark teeth belonging to the megatoothed shark before, Mullaly’s find was the first time a set had been discovered in Australia, and only the third time a set of teeth belonging to the same individual Carcharocles angustidens had been found in the world.
With a team of paleontologists, Fitzgerald and Mullaly returned to the beach last year. When the tide was low enough, the team uncovered more than 40 shark teeth from the boulder and part of the giant shark’s vertebrae. Fitzgerald said that each Carcharocles angustidens tooth they found came from a different spot in the shark’s jaw, which meant that all of the teeth most likely came from the same individual megashark.
“The teeth were finely serrated and sharper than a steak knife,” Fitzgerald said. “They are still sharp, even 25 million years later.”
Mullaly donated the teeth to the Melbourne Museum, where they are on display until Oct. 7. Nicholas St. Fleur
THE STUFF THAT HELPS LEECHES GET THEIR FILL OF BLOOD
Go for a swim in the wrong shallow lake, and you’ll emerge covered in sleek black bloodsuckers that have decided you’re their next meal.
But inside a leech, fascinating things are happening.
The slimy creatures manufacture a wide portfolio of substances that help keep blood flowing once they have attached themselves to a host. They don’t just latch on to you — they pump out anticoagulants that prevent the wounds they create from clotting too quickly. How else are they going to get their fill?
And once they have sucked your blood — they can consume many times their own body weight in one sitting, or rather, sucking — they’re not done. Leeches must also keep the blood from solidifying in their own digestive tract long after they have let go of their host.
“We’ve had leeches that can live off a single blood meal for a year,” said Michael Tessler, a researcher at the American Museum of Natural History who is a co-author of a recent paper on leeches in the Journal of Parasitology, which focused on the anticoagulant genes in leeches’ salivary organs.
Medicinal leeches, which have minuscule jaws and which doctors may use to keep blood flowing in the treatment of injuries that might otherwise lead to amputation, have been examined like this before. But Tessler and his colleagues chose eight less-studied types of marine leeches that can feed on creatures like turtles, fish and even sharks.
The researchers collected the leeches’ salivary organs and looked to see what genes were active, and compared the sequences to a database of known anticoagulants to make their identifications. In each of the species they looked at, they found an average of 43 different genes for anticoagulant substances at work. They were surprised to find that despite the leeches’ differing taste in hosts, they made many of the same anticoagulants.
The team had thought that perhaps leeches feeding on turtles and sharks would be very different, Tessler said, but that was not the case.
One substance, called destabilase, particularly intrigued the researchers because it is also common in the jawed leeches, which are a more recently evolved group.
The fact that both of these branches have the substance helps support the idea that eating blood is an ancient feature of leeches rather than a new development. Veronique Greenwood