Scientists find 16 'ultra-black' fish species that absorb 99.9% of light
These alien-like creatures are virtually invisible in the deep sea.
- A team of marine biologists used nets to catch 16 species of deep-sea fish that have evolved the ability to be virtually invisible to prey and predators.
- "Ultra-black" skin seems to be an evolutionary adaptation that helps fish camouflage themselves in the deep sea, which is illuminated by bioluminescent organisms.
- There are likely more, and potentially much darker, ultra-black fish lurking deep in the ocean.
A team of marine biologists has discovered 16 species of "ultra-black" fish that absorb more than 99 percent of the light that hits their skin, making them virtually invisible to other deep-sea fish.
The researchers, who published their findings Thursday in Current Biology, caught the species after dropping nets more than 200 meters deep near California's Monterey Bay. At those depths, sunlight fizzles out. That's one reason why many deep-sea species have evolved the ability to illuminate the dark waters through bioluminescence.
But what if deep-sea fish don't want to be spotted? To counter bioluminescence, some species have evolved ultra-black skin that's exceptionally good at absorbing light. Only a few other species are known to possess this strange trait, including birds of paradise and some spiders and butterflies.
The Pacific blackdragon
Credit: Karen Osborn/Smithsonian
When researchers first saw the deep-sea species, it wasn't immediately obvious that their skin was ultra-black. Then, marine biologist Karen Osborn, a co-author on the new paper, noticed something strange about the photos she took of the fish.
"I had tried to take pictures of deep-sea fish before and got nothing but these really horrible pictures, where you can't see any detail," Osborn told Wired. "How is it that I can shine two strobe lights at them and all that light just disappears?"
After examining samples of fish skin under the microscope, the researchers discovered that the fish skin contains a layer of organelles called melanosomes, which contain melanin, the same pigment that gives color to human skin and hair. This layer of melanosomes absorbs most of the light that hits them.
A crested bigscale
Credit: Karen Osborn/Smithsonian
"But what isn't absorbed side-scatters into the layer, and it's absorbed by the neighboring pigments that are all packed right up close to it," Osborn told Wired. "And so what they've done is create this super-efficient, very-little-material system where they can basically build a light trap with just the pigment particles and nothing else."
The result? Strange and terrifying deep-sea species, like the crested bigscale, fangtooth, and Pacific blackdragon, all of which appear in the deep sea as barely more than faint silhouettes.
David Csepp, NMFS/AKFSC/ABL
But interestingly, this unique disappearing trick wasn't passed on to these species by a common ancestor. Rather, they each developed it independently. As such, the different species use their ultra-blackness for different purposes. For example, the threadfin dragonfish only has ultra-black skin during its adolescent years, when it's rather defenseless, as Wired notes.
Other fish—like the oneirodes species, which use bioluminescent lures to bait prey—probably evolved ultra-black skin to avoid reflecting the light their own bodies produce. Meanwhile, species like C. acclinidens only have ultra-black skin around their gut, possibly to hide light of bioluminescent fish they've eaten.
Given that these newly described species are just ones that this team found off the coast of California, there are likely many more, and possibly much darker, ultra-black fish swimming in the deep ocean.
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Hungarian cartographer travels the world while mapping its treasures.
- Simple idea, stunning result: the world's watersheds in glorious colors.
- The maps are the work of Hungarian cartographer Robert Szucs.
- His job: to travel and map the world, one good cause at a time.
The world<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUyNS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzMzU3Njk1M30.rRdZpcl0bfVi4oBsljHdZSbcX0New9rdLcx6fr2mD7Y/img.png?width=980" id="f982a" class="rm-shortcode" data-rm-shortcode-id="fa67421340f881d5ab91463514cf9a6d" data-rm-shortcode-name="rebelmouse-image" />
Can you spot the world's ten largest drainage basins? In order of magnitude: Amazon, Congo, Nile, Mississippi, Ob, Parana, Yenisei, Lena, Niger, Amur. Image source: Grasshopper Geography
Africa<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUyNi9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzOTI2MzI0MX0.OeTS-scZwBES4AlZAan7fBlaBkznkig5hPjgcd1j6hw/img.png?width=980" id="e987c" class="rm-shortcode" data-rm-shortcode-id="2d3a8999ed4071a123b30efc5652fee9" data-rm-shortcode-name="rebelmouse-image" />
Africa is home to the rivers with the world's second- and third-largest catchment areas: the Congo (in blue), with a basin of 1.44 million square miles (3.73 million km2), and the Nile (in red), with basin area of 1.26 million square miles (3.25 million km2). The Nile is the longest river in Africa, though (4,130 miles; 6,650 km), followed by the Congo: 2,900 miles (4,700 km). The Congo River's alternative name, Zaire, comes from the Kikongo nzadi o nzere ('river swallowing rivers'). Image source: Grasshopper Geography
Europe<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUyOS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0NTkzOTMyMH0.tq5fjnq8wvLqXY0C9gzfoUd0ahOAQ7IZQxbpVnC1FdY/img.png?width=980" id="a8ec4" class="rm-shortcode" data-rm-shortcode-id="1ce5f59691501103343e080905ce74a3" data-rm-shortcode-name="rebelmouse-image" />
The Volga (in yellow) is the river with the biggest catchment area in Europe (just under 545,000 square miles; 1.41 million km2). It flows exclusively through Russia, and the catchment area is entirely within Russia as well. Europe's number two is the Danube (in orange), which flows through 10 countries — more than any other river in the world. Its drainage basin (just over 307,000 square miles; almost 796,000 km2) includes nine more countries. Image: Grasshopper Geography
Germany<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzMC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0Mzk4ODA3Nn0.qX1sOfJWAI7TUbTQCiIob-R5p4_wj299wEtrYAUREmg/img.png?width=980" id="d5efa" class="rm-shortcode" data-rm-shortcode-id="8e73c53d75840f21b4f2ca4b8a1e7f51" data-rm-shortcode-name="rebelmouse-image" />
The hydrographic map of Germany is dominated by just four major drainage systems: the Danube (in orange) in the south, the Rhine (in blue) in the west, the Elbe (in purple) in the east and the Weser (in green) between the latter two. In Antiquity, the Rhine was the border between the Roman Empire and the Germans. Rome once attempted to shift the border to the Elbe, which would have radically altered the course of history, but it suffered a massive defeat in 9 CE at the Teutoburger Wald (roughly between both rivers). Image: Grasshopper Geography
Great Britain and Ireland<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzMS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY1OTk2MjM3MX0.nDy__OLIyC1arty4_2xd54fjTzmfsIZo-2pe5QRjjA4/img.png?width=980" id="31a6f" class="rm-shortcode" data-rm-shortcode-id="d089f66097f37a10ab854eaccdac3581" data-rm-shortcode-name="rebelmouse-image" />
Both Ireland and Great Britain are islands, as a result of which neither boasts a continental-class river. Twenty of the 30 longest British rivers are less than 100 miles (160 km) long. The longest river in Britain is the Severn (220 miles, 354 km), its catchment area shown in blue in the southwest. Ireland's longest river is the Shannon (224 miles, 360 km). Even combined they're not as long as France's Seine (483 miles, 777 km). Image: Grasshopper Geography
United States<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzNC9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY2MDYyMzEyM30.7S_83dA6bcLyID_7BhH1R_OTy61tpgDZrBMQ_iPwnjM/img.png?width=980" id="a879d" class="rm-shortcode" data-rm-shortcode-id="a7c74a7b5a7887fb2d13b40d5d96223c" data-rm-shortcode-name="rebelmouse-image" />
Spread-eagled across the central part of the United States, the Mississippi's drainage basin covers all or parts of 32 U.S. states (and two Canadian provinces). The easternmost point of Ol' Man River's catchment area is really far east: Cobb Hill in northern Pennsylvania. Here rises the Allegheny, tributary of the Ohio, which in turn flows into the Mississippi at Cairo, Illinois. Image: Grasshopper Geography
Washington State<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzNS9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTY0MzU2MzM4OH0.mniqbkEQq84rNaWOQIl4fB4mOhNdJf5WactNyE_VsyM/img.png?width=980" id="adc4d" class="rm-shortcode" data-rm-shortcode-id="97eb5a5add49c06ef00ff0bca812b380" data-rm-shortcode-name="rebelmouse-image" />
Even leaving out the Mississippi, there's enough going on in the rest of North America to keep the eye occupied. Here's a drainage map of Washington State. The big fish in this much smaller pond is the Columbia River (drainage area in blue), the largest river in the Pacific Northwest. Only in the western third of the state is there a colourful counterpoint, in the multitude of smaller river basins that are draining into the Pacific or into Puget Sound. Image: Grasshopper Geography
Australia<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzNi9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYzOTM0ODM2NH0.U7vckwnoNoxf-bk8SuYO246hNMpR2zXILILsd4pas9o/img.png?width=980" id="38c2b" class="rm-shortcode" data-rm-shortcode-id="0c44d30d61c6cb94b8d5c7205cbabd58" data-rm-shortcode-name="rebelmouse-image" />
At 1,558 miles (2,508 km), the Murray is Australia's longest river. It is often considered in conjunction with the Darling (915 miles, 1,472 km), the country's third-longest river, which flows into the Murray. The Murray-Darling basin (in blue, in the southeast) covers just under 410,000 square miles (1.06 million km2), or 14 percent of Australia's total territory. Don't let that spidery network of river courses in the interior fool you: Australia is the world's driest inhabited continent (Antarctica, bizarrely, is drier). Image: Grasshopper Geography
Russia<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8xOTE0MjUzNy9vcmlnaW4ucG5nIiwiZXhwaXJlc19hdCI6MTYwNzg5MzIxOX0.WhShHLjjWdEh4FF_OZsY1oTN3Vc77X29TbMYbVHrHqA/img.png?width=980" id="f5cee" class="rm-shortcode" data-rm-shortcode-id="53acd93f1ab67be979e6ab128c144ce6" data-rm-shortcode-name="rebelmouse-image" />
Four of the world's largest drainage basins are in Russia: the Ob, Yenisei and Lena (origin of Vladimir I. Ulyanov's nom de guerre, Lenin) entirely and the Amur, shared with China. The Volga may be Europe's longest river, but 84 percent or Russia's surface water is east of the Urals, in Siberia. The sparsely-populated region is traversed by 40 rivers longer than 1,000 km. Combined, the Ob, Yenisey and Lena rivers cover a drainage area of about 8 million km2, discharging nearly 50,000 m3 of water per second in the Arctic. Image: Grasshopper Geography
The images and our best computer models don't agree.
A trio of intriguing galaxy clusters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQzNDA0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTkzNzUyOH0.0IRzkzvKsmPEHV-v1dqM1JIPhgE2W-UHx0COuB0qQnA/img.jpg?width=980" id="d69be" class="rm-shortcode" data-rm-shortcode-id="2d2664d9174369e0a06540cb3a3a9079" data-rm-shortcode-name="rebelmouse-image" />
The three galaxy clusters imaged for the study
Mapping dark matter<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="d904b585c806752f261e1215014691a6"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/fO0jO_a9uLA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The assumption has been that the greater the lensing effect, the higher the concentration of dark matter.</p><p>As scientists analyzed the clusters' large-scale lensing — the massive arc and elongation visual effects produced by dark matter — they noticed areas of smaller-scale lensing within that larger distortion. The scientists interpret these as concentrations of dark matter within individual galaxies inside the clusters.</p><p>The researchers used spectrographic data from the VLT to determine the mass of these smaller lenses. <a href="https://www.oas.inaf.it/en/user/pietro.bergamini/" target="_blank" rel="noopener noreferrer">Pietro Bergamini</a> of the INAF-Observatory of Astrophysics and Space Science in Bologna, Italy explains, "The speed of the stars gave us an estimate of each individual galaxy's mass, including the amount of dark matter." The leader of the spectrographic aspect of the study was <a href="http://docente.unife.it/docenti-en/piero.rosati1/curriculum?set_language=en" target="_blank">Piero Rosati</a> of the Università degli Studi di Ferrara, Italy who recalls, "the data from Hubble and the VLT provided excellent synergy. We were able to associate the galaxies with each cluster and estimate their distances." </p><p>This work allowed the team to develop a thoroughly calibrated, high-resolution map of dark matter concentrations throughout the three clusters.</p>
But the models say...<p>However, when the researchers compared their map to the concentrations of dark matter computer models predicted for galaxies bearing the same general characteristics, something was <em>way</em> off. Some small-scale areas of the map had 10 times the amount of lensing — and presumably 10 times the amount of dark matter — than the model predicted.</p><p>"The results of these analyses further demonstrate how observations and numerical simulations go hand in hand," notes one team member, <a href="https://nena12276.wixsite.com/elenarasia" target="_blank">Elena Rasia</a> of the INAF-Astronomical Observatory of Trieste, Italy. Another, <a href="http://adlibitum.oats.inaf.it/borgani/" target="_blank" rel="noopener noreferrer">Stefano Borgani</a> of the Università degli Studi di Trieste, Italy, adds that "with advanced cosmological simulations, we can match the quality of observations analyzed in our paper, permitting detailed comparisons like never before."</p><p>"We have done a lot of testing of the data in this study," Meneghetti says, "and we are sure that this mismatch indicates that some physical ingredient is missing either from the simulations or from our understanding of the nature of dark matter." <a href="https://physics.yale.edu/people/priyamvada-natarajan" target="_blank">Priyamvada Natarajan</a> of Yale University in Connecticut agrees: "There's a feature of the real Universe that we are simply not capturing in our current theoretical models."</p><p>Given that any theory in science lasts only until a better one comes along, Natarajan views the discrepancy as an opportunity, saying, "this could signal a gap in our current understanding of the nature of dark matter and its properties, as these exquisite data have permitted us to probe the detailed distribution of dark matter on the smallest scales."</p><p>At this point, it's unclear exactly what the conflict signifies. Do these smaller areas have unexpectedly high concentrations of dark matter? Or can dark matter, under certain currently unknown conditions, produce a tenfold increase in lensing beyond what we've been expecting, breaking the assumption that more lensing means more dark matter?</p><p>Obviously, the scientific community has barely begun to understand this mystery.</p>
Scientists have found evidence of hot springs near sites where ancient hominids settled, long before the control of fire.