Marine biologists have recently made a remarkable discovery – they found 16 species of “ultra-black” fish that absorb more than 99% of the light that hits their skin, making them virtually invisible to other deep-sea creatures. The researchers, who published their findings in Current Biology, caught the species after dropping nets more than 200 meters deep near California’s Monterey Bay.

At those depths, sunlight fades out, which is one reason why many deep-sea species have evolved the ability to emit light through bioluminescence. However, to counteract bioluminescence, some species have evolved ultra-black skin that absorbs light exceptionally well. Only a few species, including birds of paradise and some spiders and butterflies, are known to have this strange feature.

When the researchers first saw the deep-sea species, it wasn’t immediately obvious that their skin was ultra-black. Marine biologist Karen Osborn, a co-author of the study, noticed something unusual about the photos she took of the fish. She said that she had tried to take pictures of deep-sea fish before, but all she got were really horrible pictures where you couldn’t see any detail. She was puzzled when she shone two strobe lights at the fish and all the light disappeared.

After examining samples of fish skin under the microscope, the researchers discovered that the fish skin contained a layer of organelles called melanosomes, which held melanin, the same pigment that gives color to human skin and hair. This layer of melanosomes absorbs most of the light that hits it, with any unabsorbed light being scattered into the layer and absorbed by neighboring pigments. This creates a super-efficient system where the fish can build a light trap with just pigment particles and nothing else.

The result of this super-efficient light trap is strange and terrifying deep-sea species, such as the crested bigscale, fangtooth, and Pacific blackdragon, which appear in the deep sea as barely more than faint silhouettes. Interestingly, this unique disappearing trick wasn’t passed on to these species by a common ancestor; they each developed it independently. As such, 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 is relatively defenseless.

Other fish, like the oneirodes species, which use bioluminescent lures to bait prey, evolved ultra-black skin to avoid reflecting the light they emit. Meanwhile, species like C. acclinidens only have ultra-black skin around their gut, possibly to hide the light of bioluminescent fish they’ve eaten.

The newly described species are just a few of the ultra-black fish that exist in the deep sea. Given that these species were found off the coast of California, there are likely many more, and possibly much darker, ultra-black fish swimming in the deep ocean. The discovery of these ultra-black fish is an exciting reminder of the many mysteries that still exist in the deep sea, and of the importance of studying and understanding these strange and fascinating creatures.

The ultra-black fish are a unique example of how evolution can create a variety of adaptations to help species survive and thrive in their environment. These species have evolved to absorb light, making them nearly invisible in the dark waters of the deep sea. This ability helps them avoid detection by predators and prey and makes them better equipped to hunt and survive.

The discovery of these ultra-black fish highlights the incredible diversity of life that exists in the deep sea. The deep sea is one of the largest and least explored habitats