News and notes about science
A shallow answer on fish evolution
More than 400 million years ago, ancient oceans were teeming with many fish that might seem alien in today’s seas.
Back then some wore plates of bony armor and lacked jaws, such as the arandaspids, which looked like a clam with a tail. The heterostracans sometimes resembled underwater armadillos with spikes. There were also galeaspids, some of which sported swordlike helmets, and the osteostracans, which had horseshoe-shaped heads.
Not all jawless fish were heavily armored. The thelodonts, for example, had torpedo-shaped bodies and bony scales that looked like shark skin. Some anaspids had scales and a leaf-shaped body.
Scientists have long wondered where in the sea these extinct fish groups and their living relatives first evolved. Was it the open ocean? Perhaps on coral reefs? Or maybe in the depths of the abyss?
Now, a new study suggests that fish first swam in the shallows around the coasts of supercontinents before they diversified and conquered the world’s waters. The findings, published recently in the journal Science, also provide insight into the origins of the vertebrates that became the forebears of our ancestors who first ventured onto land.
The researchers trawled through the scientific literature and created a database with more than 2,700 fossil records of jawed and jawless fish from every continent that stretched from 480 million to 360 million years ago. The database allowed the team to determine where in the ocean the ancient fish groups lived and evolved.
“All of the groups kept originating in the shallow water over the whole 100-million-year period, which was completely unexpected,” said Lauren Sallan, a paleontologist at the University of Pennsylvania and lead author of the study. “This is an unexpected diversity hot spot that persists for a long time.”
The team is not exactly sure why fish evolved near the coast in clear, shallow lagoons and intertidal zones that were typically no deeper than about 100 feet. They think it may have to do with the waves, sea level changes, runoffs, rainfalls and other environmental factors of shallow water habitats.
“We’ve come to the suspicion that there’s something going on with water chemistry and potentially with oxygen levels in these active and dynamic environments,” said Ivan Sansom, a paleobiologist from the University of Birmingham in England and an author on the paper. Nicholas St. Fleur
Genes that make antlers grow — fast
Every spring, male deer undertake a unique biological ritual: sprouting and rapidly regrowing their massive, spiky antlers.
A complex matrix of bone, living tissue and nerve endings, deer antlers can reach 50 inches long and weigh more than 20 pounds before they are shed in winter. Not only are the antlers useful in attracting mates and fighting, they qualify deer as the only mammal that can regrow lost body parts.
Now, researchers say they have identified the two genes primarily responsible for antler regeneration in one species, fallow deer. The study, reported recently in the Journal of Stem Cell Research and Therapy, notes that these genes are also found in humans, potentially opening new avenues of research into bone trauma and diseases.
“Deer antler formation shares similar biological mechanisms with human bone growth, but deer antlers grow much faster,” said Peter Yang, an orthopedic researcher at the Stanford University School of Medicine and senior author of the study. Perhaps by studying the newly identified genes in humans, scientists may be able to develop treatments that could “reproduce the rapid bone growth of deer antlers in human bone,” and provide relief for people who suffer ailments like osteoporosis.
Yang and his colleagues traveled to a deer farm in California to take samples of early antler tissue — which consists primarily of stem cells — from male red deer. After analyzing the genes in the samples, the researchers tried shutting down some and “revving up” others to determine which function they controlled. They compared samples of RNA — molecules that deliver messages in genes — from the antlers with human RNA in search of overlaps. They then tinkered with the relevant genes in mice to see how they affected tissue growth.
The team eventually narrowed their focus to two genes, uhrf1 and s100a10, both of which have previously been linked to bone development in humans. They found that when the uhrf1 gene was shut down, the rate of bone growth in the mice significantly slowed. And when the s100a10 gene was put into overdrive, calcium deposits increased and the engineered cells mineralized more rapidly.
Yang and his team concluded that uhrf1 and s100a10 work in tandem to generate rapid antler growth in deer: uhrf1 promotes tissue generation, and s100a10 supports the hardening, or mineralization, of that tissue. Douglas Quenqua
A rare look at recent undersea eruption
In 2015, an international team of researchers sent robotic submersibles beneath the waves north of Guam. They had set out to study an area south and west of the Mariana Trench — the deepest groove in Earth’s oceans — and an arc of volcanoes, hoping to spy hidden hydrothermal vents.
Instead, they discovered a spectacular glassy labyrinth, nearly 3 miles below sea level. It was recently cooled lava, the product of the deepest underwater volcanic eruption ever recorded by scientists.
The researchers reported their discovery in Frontiers in Earth Science. The identification of deepsea eruptions happens very rarely, said Bill Chadwick, a seafloor geologist at the NOAA Pacific Marine Environmental Laboratory in Oregon and lead author of the new study, and discovering one “is an opportunity to learn about a fundamental Earth process that we know little about.”
The finding was not just notable for its extraordinary depth. The extremely young age of the lava deposit offers scientists a window into the very beginnings of what happens when a volcanic outburst occurs beneath the seas. So often, they just see an epilogue.
“Much of what we know about underwater eruptions, their hydrothermal systems and the biological communities that grow on them is gained from studying old, even ancient, volcanic systems,” said Rebecca Williams, a volcanologist at the University of Hull in England, who was not involved in the research.
Around 80 percent of Earth’s eruptions take place within the oceans. But their depth and remoteness makes finding these near-ubiquitous events difficult.
Chadwick’s team made the initial discovery using an autonomous vehicle named Sentry, which was built by the Woods Hole Oceanographic Institution. Back in 2015, it was perusing the seafloor near where the Pacific tectonic plate is sinking beneath the Philippine Sea plate. To the east, there is the Mariana Trench and an arc of about 60 underwater volcanic monuments.
To the west of this arc, the seafloor is slowly spreading. Here, in what is known as the Mariana back-arc, additional volcanic activity is possible — and this is where
Wildebeest is one highly toned machine
This time of year, the temperature routinely reaches 104 degrees Fahrenheit in northern Botswana. The grasses recede, forcing herds of wildebeest to walk farther and farther from their only water source to graze. Humidity falls to about 10 to 15 percent.
“It’s not quite Death Valley, but it’s not quite far off it,” said Alan Wilson, a biologist whose research examined how the wildebeests cope with such an inhospitable environment. “They’re on a physiological knife edge in terms of: How do they continue to survive?”
His research showed that these cowlike animals, also called gnus, have remarkable adaptations, enabling them to walk up to 50 miles over five days without drinking water. They can do this because their muscles work incredibly efficiently — far more than their body size would suggest.
“I don’t think we’d get to 50 miles,” Wilson said, referring to humans.
His study, published in the journal Nature, showed that this efficiency means wildebeests do not have to sweat or pant as much to release heat, even when they are running in heat higher than their body temperature.
“They don’t have the problem of overheating that they would have otherwise or having to use water to cool themselves,” said Andrew Biewener, an expert in the biomechanics at Harvard University who was not involved in the research.
The new research indicated that the muscles of large animals are generally more efficient, with cows at about 42 percent efficient. The wildebeests clocked in well above their size at 63 percent efficiency. Sentry spotted the prolific lava flows.
Old lava flows were expected here, but what the researchers detected is the first known new eruption in the back-arc region. That makes this discovery enormously serendipitous, as eruptions here are only expected every few hundred years or so. Robin George Andrews