Science news in brief: Starfish have eyes and beetles make toads regret eating them

Science

Starfish see well in the deep ocean – yes, they have eyes

Look at a starfish in a tidal pool and you may think, ah, there’s one of those pretty, multi-armed sea worms that crawl around and don’t do much. But look deeper and your views might change.

Hundreds of feet below the ocean’s surface, some starfish make their own light. And they can look right back at you too, with a teeny eye on the tip of each bendy starfish arm.

Scientists who didn’t even know if deep sea starfish had eyes did not expect to find this. They collected starfish from Arctic waters off Greenland’s coast to determine which species had eyes and, for those that did, how well they could see.

The researchers found that some starfish are far more biologically complex than previously thought, after looking at the structures of their eyes, their behaviour in a simulated environment, whether they glowed in the dark and what tasks in the wild would make eyesight useful.

“Even in places where the sun don’t shine, it’s far from dark,” says Anders Garm, a marine biologist at the University of Copenhagen who led the study, published in Proceedings of the Royal Society B. “There are animals there making their own lanterns and finding their way.”

Scientists thought deep sea starfish would be eyeless or at the most have very simple eyes. But as they examined specimens they retrieved, they found that many starfish had unexpected visual tools.

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Japanese common toad: some species are better at digesting ‘the farting bug’ than others (Creative Commons)

Toads eat beetles, but sometimes beetles make them regret it

For most prey, the game is over once they have been swallowed. But one species of beetle can escape from a toad’s stomach nearly two hours after being eaten, according to a new study.

Found in wooded areas on nearly every continent, bombardier beetles – a group that consists of more than 500 species – get their name from their signature defence mechanism: When threatened, they shoot a hot chemical spray from their rear end. In Japan, the insects have long been known as “the farting bug”.

Toads have been observed vomiting bombardier beetles after eating them, but no one knew exactly why or how long the beetles survived after their brush with digestion.

To better understand the beetle’s defences, two biologists from Kobe University fed a species of bombardier beetle to two different species of toad collected from forests in central Japan. One toad species shared its natural habitat with that particular species of beetle, while the other was unlikely to encounter it in the wild.

After the beetles were swallowed, a small explosion could be heard inside each toad, indicating that the insects were firing their defences. Overall, 43 per cent of the toads vomited the beetles, taking anywhere from 12 to 107 minutes.

Most important (at least to the insects): despite being covered in mucus, meaning they had entered the toads’ digestive system, every evicted beetle was still alive, and all but one survived for another two weeks. No toads died on account of eating the beetles.

But some toads were better able to digest the beetles than others. Only 35 per cent of the toads that shared habitat with the beetles coughed them up, compared with 57 per cent of the toads with no common habitat. The findings suggest that regular exposure to bombardier beetles has allowed some toads to evolve a tolerance to their poison.

4,400-year-old tomb discovered in Egypt

Archaeologists in Egypt have discovered a 4,400-year-old tomb near Cairo that contains rare wall paintings and is believed to belong to a high-ranking Egyptian priestess.

The tomb, near the Giza pyramids, is thought to be that of a priestess named Hetpet.

“The tomb is in very good condition,” Mostafa Waziri, secretary-general of the Supreme Council of Antiquities, says. “There are coloured depictions of traditional scenes: animals grazing, fishing, bird-catching, offerings, sacrifice, soldiers and fruit-gathering.”

Hetpet was a priestess for Hathor, a goddess depicted as a cow and associated with fertility, motherhood and love. The priestess is believed to have been close to ancient Egyptian royals of the Fifth Dynasty.

Scenes on the tomb’s walls show Hetpet hunting and fishing. The walls also included images of dancing and musical performances, as well as monkeys, which were domestic pets at the time, Khaled el-Enany, the Egyptian antiquities minister, said at the site of the tomb, which is from about 2400BC.

These skates are made for walking

About 375 million years ago, a pioneering fish crawled out of a prehistoric ocean and kickstarted the evolution of salamanders, lizards, you, me and all other land vertebrates that have ever existed.

The brain circuits of neurons that govern walking, many have long thought, emerged sometime after that, as creatures transitioned from swimming to limb-based locomotion.

But a new report, published in the journal Cell, overturns that notion, suggesting the template for walking originated in ancient fish millions of years before the first vertebrate ever ambled on dry land.

The little skate, a fish closely related to sharks and rays, not only displays walking behaviour on the sea floor, but uses neurons and genes that are nearly identical to the ones vertebrates use to walk on land, says Jeremy Dasen, an associate professor at the NYU School of Medicine’s Neuroscience Institute and senior author of the paper.

You can trace the heritage of little skates and land vertebrates back to a common ancestor that lived about 420 million years ago. This primitive fish gave rise to the vast majority of vertebrate species, including all fish with paired fins. Typically, these pectoral and pelvic fins – which correspond to forelimbs and hindlimbs in land vertebrates – are small and largely used for balance and steering. To really propel themselves, most fish wriggle their powerful tails.

Little skates, which are commonly found along the US east coast, do not really wriggle. Instead, they flap and flutter enormous pectoral fins to swim in a style that resembles flying. On the sea floor, they scamper with their pelvic muscles, alternating left and right fins in a sequence that looks strikingly like walking.

In land vertebrates, or tetrapods, walking is partly characterised by this left-right alternation as well as rhythms of extending and flexing. These patterns are governed by networks of neurons that work together to inhibit and activate complementary types of muscles. When excitatory neurons are firing in your left leg muscles, for example, inhibitory ones are firing in your right. Similarly, as some neurons tell your extension muscles to contract, others tell your flexion ones to relax.

At the site of a Japanese volcano’s super-eruption, an immense lava dome lurks

Some 7,300 years ago, a super-eruption devastated the southern islands of what is now Japan, burying most of the archipelago in thick ash. Known as the Akahoya eruption, the blast was so powerful it caused the volcano’s magma chamber to collapse, leaving a 12-mile wide scar called Kikai Caldera, which is mostly underwater.

In a new study, scientists have discovered that a dome of lava lurks beneath the caldera. By studying its magma plumbing, volcanologists could gain insight into the entire caldera system, which could help them better predict when another eruption in the Japanese archipelago might occur.

“The most serious problem that we are worrying about is not an eruption of this lava dome, but the occurrence of the next supereruption,” says Yoshiyuki Tatsumi, a volcanologist at Kobe University in Japan and lead author of the study that appears in the journal Scientific Reports.

Tatsumi’s previous work has suggested that the chances of a super-eruption happening in the Japanese archipelago in the next century are only about 1 per cent. But if a volcano in this area erupts, it could eject nearly 10 cubic miles of magma, covering almost all of the country and its 120 million people in nearly 8in of thick ash, he found.

He and his colleagues at the Kobe Ocean Bottom Exploration Centre conducted three surveys of the caldera, during which they used remotely operated vehicles to observe the depression. On their trips they investigated the caldera using seismic analysis as well as geological and electromagnetic tests. They found the lava dome using an acoustic survey.

The dome – a trapped buildup of viscous lava – is estimated to have a volume of about 8 cubic miles, a diameter of about 6 miles and a height of almost 2,000ft. While other volcanic remnants, like the Yellowstone caldera and the Long Valley caldera, have also been brewing with activity, the paper noted that this dome has a much more immense volume of lava.

© New York Times

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