Anemonefish can see ultraviolet light


This 2017 video is called Amphiprion akindynos 澳洲藍帶成魚Barrier reef anemonefish.

From the University of Queensland in Australia:

Finding Nemo’s cousins: Meet the little fish that can see UV light

November 11, 2019

Summary: New research reveals anemonefish can see UV light and may use it as a secret channel find their friends and food, while evading predators.

The fish made famous in Finding Nemo can see ultraviolet (UV) light and may use it as a ‘secret channel’ to find both friends and food, according to researchers.

Anemonefish are easily recognised by their striking orange and white patterning, but University of Queensland scientists set out to find out how ‘clownfish‘ see their world and how that influences their behaviour.

Researchers at UQ’s Queensland Brain Institute (QBI) and the University of Maryland (USA) analysed the visual systems of a particular species of anemonefish, Amphiprion akindynos.

QBI researcher Dr Fabio Cortesi said the Great Barrier Reef anemonefish was basically Nemo’s cousin.

“We looked at everything starting with the genes they use to see and what proteins they express, and in combination with anatomical data, predicted what these anemonefish can see,” he said.

“Proteins involved in detecting light have minute, well-known differences that influence which wavelengths of light they absorb.”

QBI researcher Dr Fanny de Busserolles, who shares lead authorship on the study with Dr Sara Stieb, said the team was able to discover a unique specialisation in the eye of the fish that may allow them to better detect friends and their anemone.

“In the part of the anemonefish’s eye that looks forward, the photoreceptors detect a combination of violet light and ultraviolet light,” Dr de Busserolles said.

“They seem to be very good at distinguishing colour, and very good at seeing UV — it looks like they use it a lot.”

Dr Sara Stieb said the special ability made sense, based on the fish’s environment and food source.

“Anemonefish live very close to the surface, where UV light can easily penetrate,” Dr Stieb said.

“They live in symbiosis with anemones, and the anemones use UV to grow.

“Moreover, anemonefish feed on zooplankton which absorb UV light, so it would appear like dark dots against the background, making it easy to find.”

Dr Cortesi said UV vision lent anemonefish another important advantage.

“Their visual system seems to be very tuned to recognising who is their friend and who is not,” he said.

“The white stripes on anemonefish reflect UV, which means they should be easier for other anemonefish to recognise.

“By contrast, a lot of the bigger fish — including ones that eat anemonefish — cannot see UV, so if you want to communicate on the reef over short distances, then UV is a very good way to do this.

“UV is essentially a secret channel that only these little fish can use to talk to each other,” he said.

“They can be as flashy as they want and they won’t be seen — and it might be how Nemo’s cousin finds its friends.”

The findings have been published in the journal Scientific Reports.

Fish swimming in schools, new research


This August 2017 video says about itself:

Shimmering schools of fish have dazzled scientists for centuries with their synchronized maneuvers. Now, high-speed video is revealing how—and why—they do it.

From New York University in the USA:

Best ‘classroom’ shapes for fish swimming in schools

November 4, 2019

A team of researchers has identified the best arrangements for fish swimming in schools — formations that are superior in terms of saving energy while also optimizing speed. Its findings, which appear in the journal Physical Review X, point to potential new ways to enhance energy-producing technologies.

The work, conducted by researchers at New York University’s Courant Institute of Mathematical Sciences, also confirms a long-held belief: fish swimming in orderly groups or formations spend less energy and move faster than when swimming alone.

“Animals have figured out some interesting tricks that can save energy and move faster, and these behaviors could translate into new energy-harvesting and propulsion devices,” says Leif Ristroph, an associate professor at the Courant Institute and one of the paper’s co-authors. “Our model could inform how to optimize such technologies.”

Using a new type of mathematical model, the team, which also included Michael Shelley, a professor at the Courant Institute, and Anand Oza, an assistant professor at the New Jersey Institute of Technology, focused on several arrangements of swimmers to see which were the best in terms of saving the energy required to swim and enhancing the speed of swimming for the group. In particular, using computer simulations, they examined how multiple flapping swimmers emit vortices, or swirling flows, and also interact with the vortex flows produced by others in the school.

In every school formation tested, the group of swimmers used less energy and moved faster than did solitary swimmers, with some notable differences among these arrangements:

  • Phalanx arrangements, in which fish are lined up side-by-side, showed modest improvements over a solitary swimmer;
  • Tandem formations, in which fish are lined up single file one after another, showed even more improvement over a solitary swimmer;
  • Rectangular lattice formations — which combine the phalanx and tandem formations so that each fish has neighbors directly upstream, downstream and to either side — were superior to both the tandem and phalanx schools;
  • Diamond-shaped lattices, in which each fish has one direct upstream neighbor as well as two neighbors upstream and somewhat displaced to each side, yielded the greatest speeds and largest energy savings — i.e., the best formation tested.

The researchers note that both the phalanx and diamond-lattice formations have been observed in fish schools, with smaller schools tending to adopt a phalanx formation and larger schools choosing a diamond lattice.

“By formulating a mathematical model capable of handling many swimmers interacting through their collectively generated flows, we think we have offered some concrete support for the idea that schooling fish may benefit from flow interactions,” observes Ristroph. “We also hope to apply these same methods to other related problems — for example, flying formations of birds.”

Prehistoric rhino discovery in Yukon, Canada


This 18 June 2019 Canadian TV says about itself:

A pair of fossilized teeth found in Yukon in the 1970s belong to a species of ancient hyena that roamed the grassy tundra during the early years of the last ice age, paleontologists have found. The fossils sat in the Canadian Museum of Nature in Ottawa until Jack Tseng, an expert on ancient predatory mammals, was brought in to confirm that they are the first hyena fossils found in the Arctic.

From the University of Colorado at Boulder in the USA:

Ancient rhinos roamed the Yukon

October 31, 2019

Summary: Paleontologists have used modern tools to identify the origins of a few fragments of teeth found more than four decades ago by a schoolteacher in the Yukon.

In 1973, a teacher named Joan Hodgins took her students on a hike near Whitehorse in Canada’s Yukon Territory. In the process, she made history for this chilly region.

While exploring the tailings left behind by a now-defunct copper mine, Hodgins and her students stumbled across a few fragments of fossils — bits and pieces of what seemed to be teeth alongside pieces of bone.

The ancient fragments of teeth were so small and in such bad shape that “most paleontologists may not have picked them up”, said Jaelyn Eberle, a curator of fossil vertebrates at the University of Colorado Boulder’s Museum of Natural History.

But Hodgins did. Now, more than 40 years after the teacher’s fateful hike, an international team led by Eberle used modern technology to identify the origins of those enigmatic fossils.

In a study published today, Eberle and her colleagues report that the fossil tooth fragments likely came from the jaw of a long-extinct cousin of today’s rhinoceroses. This hefty animal may have tromped through the forests of Northwest Canada roughly 8 to 9 million years ago.

And it’s a first: Before the rhino discovery, paleontologists had not found a single fossil vertebrate dating back to this time period in the Yukon.

“In the Yukon, we have truckloads of fossils from ice age mammals like woolly mammoths, ancient horses and ferocious lions”, said Grant Zazula, a coauthor of the new study and Yukon Government paleontologist. “But this is the first time we have any evidence for ancient mammals, like rhinos, that pre-date the ice age.”

It’s a gap in the fossil record that scientists have been keen to fill.

To understand why, imagine the Earth during the Tertiary Period, a span of time that began after the dinosaurs went extinct and ended about 2.6 million years ago. In that age, a land bridge called Beringia connected what are today Russia and Alaska.

Paleontologists believe that animals of all sorts, including mammoths and rhinos, poured over that bridge.

There’s just one problem: The geology and environment of the Yukon, which sat at the center of that mass migration route, isn’t conducive to preserving fossils from land animals.

“We know that a land bridge must have been in operation throughout much of the last 66 million years,” Eberle said. “The catch is finding fossils in the right place at the right time.”

In this case, the people at the right place and at the right time was a Yukon schoolteacher and her students.

When Eberle first saw Hodgins’ fossil teeth, now housed in the Yukon Government fossil collections in Whitehorse, she didn’t think she could do much with them.

Then she and her colleagues landed on an idea: Eberle put one of the small pieces under a tool called a scanning electron microscope that can reveal the structure of tooth enamel in incredible detail.

She explained that mammal teeth aren’t all built alike. The crystals that make up enamel can grow following different patterns in different types of animals, a bit like a dental fingerprint. The Yukon tooth enamel, the team found, carried the tell-tale signs of coming from a rhinoceros relative.

“I hadn’t thought that enamel could be so beautiful,” Eberle said.

The method isn’t detailed enough to determine the precise species of rhino. But, if this animal was anything like its contemporaries to the south, Eberle said, it may have been about the same size or smaller than today’s black rhinos and browsed on leaves for sustenance. It also probably didn’t have a horn on its snout.

The group also looked at a collection of fossils found alongside the rhino’s tooth chips. They belonged to two species of turtle, an ancient deer relative and a pike fish. The discovery of the turtles, in particular, indicated that the Yukon had a warmer and wetter climate than it does today.

Hodgins, now-retired, is excited to see what became of the fossils she and her students discovered more than 40 years ago: It’s “just so wonderful to learn what has developed with them from long ago,” she said.

Eberle added that the Yukon’s newly-discovered rhino residents are a testament to the importance of museums.

“The fact that these specimens were discovered in the Yukon museum collection makes me really want to spend more time in other collections, including at CU Boulder, looking for these kinds of discoveries that are there but haven’t had the right eyes on them yet,” Eberle said.

Prehistoric reptiles and fish Top 10


This 11 October 2019 video says about itself:

Hello everybody! Today we’re going to look at some of the animals that lived before the dinosaurs. We often think of dinosaurs as the biggest, oldest creatures the Earth has ever seen. However, there are plenty of animals that pre-date the dinosaurs and they’re majestic in their own right. Top 10 prehistoric animals.

This Top 10 includes various reptile species from the Permian and Triassic, two fish species and the ancient invertebrate predator Anomalocaris.

Antarctic marine life, video


This 27 October 2019 video says about itself:

The Enchanted World Beneath the Antarctic Ice Sheet | Seven Worlds, One Planet | BBC Earth

The Seven Worlds, One Planet crew dived beneath the surface of the Antarctic ice sheet with only a tiny bore hole for escape. Discover the wonders they found in the frozen seas.

How piranha, pacu fish replace their teeth


This May 2018 video is called The Difference between Piranha and Pacu fish.

By Priyanka Runwal in Science News, October 24, 2019 at 6:00 am:

Piranhas and their plant-eating relatives, pacus, replace rows of teeth all at once

Not losing teeth individually might help distribute wear and tear from the fishes’ diets more evenly

When it comes to scary teeth, piranhas’ bite is among the most fearsome. Their razor-sharp teeth strip prey’s flesh with the ease of a butcher’s knife.

In a process that avoids dulling, the fish lose all their teeth on one side of their mouth at once, with a fresh set growing in five days later. Months later, the same thing happens on the other side of the jaw. That trait was how the carnivorous fish adapted to a diet of scales, fins and flesh, or so scientists thought.

Yet it turns out the fierce fish share this toothy trait with their plant-eating cousins, the pacu, suggesting that this tooth replacement strategy evolved earlier in the herbivorous ancestors of piranhas and pacus, scientists report in the September Evolution and Development.

That’s perhaps not so surprising, says Matthew Kolmann, a biologist at George Washington University in Washington, D.C.  Eating hard seeds and tough stems can damage fish teeth, he says. Cycling through sets of teeth, instead of replacing teeth one at a time, may help the freshwater fish more evenly distribute the wear and tear from chewing.

Kolmann and his colleagues took micro CT scans of 93 pacu and piranha museum specimens spanning 40 species. Pacus have a double row of teeth along both the upper and lower jaw, while piranhas sport a single row, like humans. The images revealed well-developed teeth embedded in the jaw parallel to teeth already in use on one side of the mouth. These mature teeth form sawlike blades that lock together as a unit, ready to erupt and replace a lost row. A microscopic look at jaw tissue also showed tiny tooth buds beginning to develop along the opposite jaw.

That means the fish are continuously developing new sets of teeth throughout out their lives. “That’s a hallmark of the whole clade”, Kolmann says, “be it species that eat meat or plants.”

Dead whale feeds deep-sea animals, videos


This 16 October 2019 video says about itself:

Whale Fall Actively Devoured by Scavengers at Davidson Seamount| Nautilus Live

During the final dive of this year’s Nautilus expedition season, our team discovered a whale fall while exploring Davidson Seamount off central California’s coast with researchers from Monterey Bay National Marine Sanctuary. The skeletal remains of the whale lying on its back are estimated to be 4-5 meters long. The team is working to identify the species, but it is confirmed to be a baleen whale as indicated by baleen remaining along the whale’s jawbones.

While evidence of whale falls have been observed to remain on the seafloor for several years, this appears to be a relatively recent fall with baleen, blubber, and some internal organs remaining. The site also exhibits an interesting mid-stage of ecological succession, as both large scavengers like eelpouts are still stripping the skeleton of blubber, and bone-eating Osedax worms are starting to consume lipids (fats) from the bones. Other organisms seen onsite include crabs, grenadier, polychaetes, and deep-sea octopus.

This 17 October 2019 video is the sequel. It says about itself:

The banquet continues! Yesterday we made a surprise baleen whale fall discovery that viewers around the globe watched alongside the Nautilus team in Monterey Bay National Marine Sanctuary. Get a close up look at some of the scavenging diners including eelpouts, octopus, and polychaete worms–like the bone-eating Osedax worms that carpet the whale’s bones in a red fringe.