Sea dragons are incredibly strange creatures, and researchers have figured out why

The image of a fragile sea dragon perched among the seaweed, decorated with leaf-like ornaments moving across ocean currents, is truly an impressive sight.

But sea dragons hide more than a diver can see. No matter how adorable they are, sea dragons also lack teeth and ribs, and their spines are curved and bent.

Now, scientists have found genetic clues that could explain why sea dragons look so amazingly distinct — not only are their genomes packed with repetitive pieces of DNA that determine their development, but they also lack a set of genes that give rise to teeth, nerves, and facial features in other animals. Science alert points out.

Exploring the sea dragon’s genome “raised a veil on the evolution of traits specific to sea dragons” and “revealed interesting evolutionary aspects of this unusual family of vertebrates”. Syngnathidaeas a whole,” writes the team behind the study.

Secrets of the sea dragons

Sea dragons belong to the same family as galleon fish and sea horses, which are famous for the development of pregnancy in males. “This group is fascinating for a number of reasons,” says evolutionary genomics researcher Clayton Small of the University of Oregon, who led the study with fellow researcher Susan Basham. “But sea dragons are cranky in a group of really strange fish.”

To find out why, Small, Bassham and the team sequenced the genomes of two sea dragon species: the leafy sea dragon and the common sea dragon, both found in the cold waters off the southern coast of Australia. Drifting along with the leaf-like ornaments that help camouflage them in rocky, algae-covered reefs, these slender fish can be hard to spot.

Elusive, in fact, that the third species of sea dragon, the rare ruby ​​sea dragon was first seen in the wild in 2017. All three types of sea dragons are revered for their colorful and adorable body shapes. For a long time, the crustaceans sucked up tube holes, but the large ruby ​​dragon seems to have lost its leafy appendage that others have exposed, and this development eliminates the extravagance.

sea ​​dragon ornaments

Scientists believe that sea dragons have evolved their extravagant features so rapidly in the past 50 million years, as they and sea horses branched out to form a new family. What is less clear is how they became so special. So in this study, researchers at the University of Oregon teamed up with scientists at Birch Aquarium at the Scripps Institution of Oceanography and the Tennessee Aquarium to analyze samples they obtained from captive-bred sea dragons.

It turns out that sea dragons, compared to their closest relatives, pipe fish and sea horses, have in their genetic code a surprisingly large number of repetitive DNA sequences called transposons, known as “jumping genes”. Transposons are so mobile that they “jump” up the genome, causing rapid genetic changes – which could explain why sea dragons evolved so quickly.

Compared to its two distant relatives, the zebrafish and the thistles, the leafy and common sea dragon genome lacks a piece of genes that play indispensable roles in other vertebrates, containing instructions on how to form facial structures, teeth, limbs, and even parts of the body or central nervous system.

Scientists speculation

While researchers have been tempted to speculate that the loss of these genes could explain how sea dragons developed elongated facial features and exquisite ornaments, more research will be needed to investigate the evolutionary history of sea dragons and their relatives. But the researchers haven’t finished imagining a sea dragon with weeds, an adult male, one foot in length, using high-resolution X-ray microscopy, which showed the ornamental limbs may have evolved from thorns.

“I could see that the supporting structures of the leaf plates looked like thorny details, with fleshy inserts added to the ends,” Basham says. The team also noted that these bony supports differ from the hardened, ossified bone found in the wings of most bony fish and instead appear to be stiffened by a core of collagen tissue, adding to the story of how the unique structures of bone emerged. The body of a sea dragon.

No matter how sea dragons evolved, the results are glorious, even filled with magic. As far as we know, sea dragons may still have some secrets hidden in their genome, which can be discovered through additional genetic comparisons.

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