According to the Smithsonian Institution website, the newly discovered "sword-shaped eye socket bone" is expected to reshuffle the relationship between these deadly fish. In 2003, Leo Smith, an evolutionary biologist at the University of Kansas, dissected a velvetfish. He wanted to find out the relationship between scorpaeniformes, which included velvet, tigerfish, stonefish, and the infamous lionfish, a generic name derived from bone plates found on each fish's cheek. While dissecting the upper jaw of the velvet, he noticed a strange spot where he could not remove the tear bone.
Smith recalled, "For normal fish, there was some connective tissue between the maxilla and this bone, and you could cut between them with a scalpel blade. But at the time I found it quite difficult to separate this structure. When I finally parted it, I noticed that the structure was uneven, and it occurred to me that there should be some kind of locking mechanism in it. His work focuses on the evolution of fish venom and the phenomenon of bioluminescence.
Most velvet sturgeon themselves look weird, with spines and drip spots all over their bodies, so this uneven structure is not so unusual. But Smith spent years studying the order, and he had never encountered such a huge locking eyegutch before. He and his colleagues called the strange newly discovered structure a "lachrymal saber."
(This is an X-ray image of Whistlered Prowfish, which has a "sword-like eye socket bone.") It is a tiger fish whose eyes glow. ）
Smith's article, published in the Journal of Amphibians and Reptiles in collaboration with some members of the American Society of Ichthyologists and Herpetologists, first described this unlikely eye prick, and they also described another small green-fluorescent eye prick. The researchers did not specify exactly what the use of this attachment was. However, they claim that the discovery of this eyegus has the potential to upend the evolutionary tree of the order Scorpene and change our understanding of these extremely toxic fish.
The discovery also raises the question: Why has this glowing, locked sword-like attachment been ignored for so long?
(A stonefish named Spotted Ghoul is half hiding in gravel.) ）
It's easy to miss the stonefish underwater. As the name suggests, the fish resemble rocks, covered in cobblestones on the outside and look like underwater rubble or coral reefs. But step on one and you'll never forget it.
There are more poisonous fish in the ocean than snakes on land, and even more than all venomous vertebrates. Stonefish are the most poisonous fish on earth. Unfortunately, being bitten by a stonefish, as one victim once described, "Strike your toes with a hammer and then rub your toes over and over again with a nail file." "There have been divers who have been bitten by stone fish and lost their lives, but this is not common.
Stonefish and their close relatives are also very good at camouflage. Some fish grow algae and hydra gardens on their backs, and some fish can change color at will. Decoy scorpionfish have bait on their dorsal fin, resembling a small swimming fish. These amazing creatures live mainly in the tropical waters of the Indo-Pacific region, using camouflage to ambush prey and avoid becoming predators of their own lunches.
The sword-shaped eye socket bone is characteristic of these fish, but this eye prick is somehow overlooked. Its structure is very special. Imagine the complex spines bulging under the fish's eye, locked into place from the side like ratchets and pawls, like two sharp arms. Smith said, "These fish move the underlying bone attached to it through a locking mechanism and then rotate the eye spikes. ”
At least one species, centropogon australis (a tiger fish), has pale yellow-green fluorescence from its eye spikes, while the rest glow orange-red under some sort of light.
Adam Summers, a biomechanicist and fish expert at the University of Washington, is currently ct scanning 40,000 species of fish. He has scanned 3,052 species of fish and 6,077 samples. Over the years he has studied many species of fish in the order Scorpene, but has never noticed the structure of the eye prick.
Summers was the scientific advisor to Pixar Animation's first and second Finding Nemo films. "The phenomenon of upright defense of fish is very common," he said. "This refers to the anatomical defenses of a certain structure of the body when certain species encounter stress or threat. "If you catch a fish and pull it off the hook, you'll feel its dorsal spines stand up and prick you all the way," he said. But for years we haven't found this structure under the eyes — the eye spurs — it's incredible. ”
The researchers used DNA sequencing to confirm their new findings. They looked at 5280 school-ranked nucleotides and used 12 outgroups as control groups to construct a pedigree or evolutionary tree. Smith explained that once the tree is in possession, the evolutionary history of certain traits can be traced using the method of ancestral sign state reconstruction. This may help biologists unify fish that used to be considered different families into the same family.
Smith explains: "In the past, the classification of the order Scorpene was confusing. The relationship between sturgeon and stonefish is indeed problematic, and many of the family names associated with them are removed when these fish are considered two main lineages instead of the 10 traditional fish families. Now that their method of differentiation is simpler, the presence or absence of eye spurs can completely distinguish the two lineages.
(In the Feld Museum, a whiskerfish, whose English name is Apistus carinatus, is eaten by a meat-eating beetle that leaves only bones.) ）
The first time he dissected the velvet, Smith didn't understand what he was looking at. He said, "I thought they were just a little bit prickly, a little rough. Their heads have many spines and bumps. So I said, 'Oh, these eye sockets are more interesting.' '”
Smith spent years dissecting fish bones and live fish to determine how common this eye prick was. Fortunately, as director of the University of Kansas Biodiversity Institute, he has access to one of the world's largest fish specimen banks.
Many of these specimens were made using a "wash and stain" method, in which scientists mixed liquid formaldehyde with a gastric enzyme called trypsin to dissolve muscles and other soft tissues. As a result, the bones are dyed red and the cartilage is dyed blue, so that the bone structure is clearly presented, like stained glass. This technique makes it easier for scientists to study the skeletal structure of vertebrates.
Summers notes that "people who study fish often have to deal with dead fish, and many of the very good techniques cannot be applied to animals that cannot move." It's really great to spot the eye and realize that it's a unifying feature of the entire school of fish. ”
Smith wasn't sure why fish evolved this trait. The obvious hypothesis is that the eye spikes have a defensive function, as the protruding spines enlarge the width of the head, making them more difficult to swallow and more likely to pierce predators. Other fish perform similar defensive measures: the dorsal spines of the deep-sea lantern shark have glowing "lightsabers," which scientists believe serve to defend against predators.
However, Smith was not sure about the defensive effect of the eye piercing. Another possibility, he says, is to attract a spouse. In other words, the true meaning of the current eye piercing is still a mystery.
In 2006, Smith, along with Ward Wheeler, found that more than 1,200 species of fish were poisonous, compared to previous estimates of about 200. Ten years later, Smith updated the species of poisonous fish to 2386 to 2962 species. He also wrote papers with renowned ichthyologists Matt Davis and John Sparks and published them in the Journal of the Public Library of Science (Plos One). The paper notes that the paper shows that the bioluminescent properties of marine fish lineages have evolved 27 times. He even modified the classification of butterflyfish.
Smith's new discovery could upend people's understanding of fish relationships, and Sarah Gibson, an associate professor of biology at St. Cloud State University in Minnesota, worked on Triassic fish. "I think this is a very significant study," she said, "and understanding the evolutionary relationships of fish populations can actually influence our understanding of the evolutionary history of fish." ”
Summers added that understanding the evolutionary history of stonefish is key to protecting them, "We need to know what they really are, otherwise conservation efforts cannot be carried out." "The Mystery of the Sword-like Eye Socket Bone" is an interesting topic worth exploring, and I am still shocked that we did not discover it before. ”
Ultimately, the discovery also validated what Smith had said to The New York Times, that despite hundreds of years of research and exploration, "we still know nothing about fish."