By dragging a bunch of dead fish in, scientists may have revealed the hidden power of mucus, one of biology’s most important substances. And what they find may help us to understand the very dawn of vertebrate life on the land.
First, it is important to know that fish are covered with a thin layer of mucus. This slimy coating (also known as “slime coat”) is known to keep fish healthy by warding off pathogens. Scientists have also discovered some evidence that mucus can reduce drag, helping fish swim more easily in the water.
Noah Bresmana physiologist at Salisbury University in Maryland studied fish mucus in hugfish, famous for its mucus. However, much of his other studies have focused on fish in the aquatic or fish species that can move both water and land. And he wanted to know if mucus might help those fish go around.
“Moving amphibious fish, basically a military roams on the ground. They are covered in mucus. The mucus is likely to affect how it moves on the land,” Bresman said. Ta Popular science. “Does it make it easier? Does it lubricate and help them move easily on land?”
To answer this question, Breathman turned his eyes to Northern Snakehead, a native of Asia fish that has become an invasive species of freshwater habitat scattered throughout the United States for the past 20 years. . Northern Snakehead You can reach out It grows to nearly 3 feet long and up to 19 pounds. And because they can breathe air from their mouths, these impressive large fish can survive and travel on land.
The first step was to catch a fish. Undergraduates at the time Breathman and Frances Lopez Chierel had snake heads from the Maryland Department of Natural Resources, which caught fish during the base investigation. However, the two researchers also learned how to fish for Snakeheads, a sport that has become popular in the US since the species was introduced. As part of the sample collection of this study, Breathman participated in and won the Snakehead Fishing Tournament.
“It led to more people getting us to measure their snakehead,” Bresman said.
Additionally, the team gathered two fish, two fish, that had not climbed to land, to compare it to the Snakehead. Carp have scale like snakehead, but catfish have no scales.
In this study, each fish was euthanized and attached to a force meter via fishing line. Researchers accurately measure and accurately measure the force that a fish has taken to start moving. The fish were dragged back and forth on a smooth plastic table and part of the artificial grass. After measuring each of these compositions, the researchers wiped each fish cleanly and dragged it again to take the same measurement without a mucus coating. They published their results in the journal on January 29th Integrated and Comparative Biology.
All fish species tended to migrate more easily when covered with mucus. That makes sense – Mukos is slippery! However, on both the table and the grass, mucus snakeheads were generally even slippery than mucus y car or mucus y catfish. (One exception was when a mucus-covered fish was pulled backwards on the grass, where there was no significant difference in slipperiness between the snake’s head and the catfish.)
Without the mucus, the snakehead was significantly more stiff to pull than either the carp or catfish on the table. On the grass, mucus-free snakeheads were slippery than carp moving backwards, but not forwards. And compared to catfish, the mucus-free snakehead was a more slippery advance, with no two species moving backwards. The team noted that when the snakeheads dry, the remaining mucus begins to feel sticky as the fish dry out, which could help increase the amount of force needed to pull them.
These results may indicate that snakeheads evolve more slippery mucus and help them move to land, the paper suggests.
“By evolving mucus that reduces friction compared to completely aquatic species like carp, it could significantly reduce the energy costs required for terrestrial movements, increasing the distance,” Blessman said. writes Lopez Cirel.
Dylan Wainwrightsaid a biologist at Purdue University who was not involved in the new research. Popular science He calls the new paper “very excited,” and the data says “a kind of integrity in a satisfying way with what you predict.”
“I think a lot about the surfaces of fish, the scales, and sometimes the mucus of my work, but there’s very little work on that,” Wainwright says. “And it was really cool to see someone else think critically about mucus.
Researching fish mucus has practical uses. For example, some scientists are trying to develop robots modeled after amphibious fish, Bresman pointed out. “What if you put the robot in artificial mucus and help it move more easily on land?” he said.
But perhaps more importantly, this new study could provide a clue to our own origins. 400 million years ago, vertebrates were not yet living on land. Everything was still swimming in the water in the backbone. Then, fish that lived in shallow coastal habitats (probably the famous fish). Tictalk) I started to lift myself up to the beach. These creatures have become the common ancestors of all frogs, birds and humans living today.
It is not known whether mucus played a role in this monumental moment in evolutionary history. But these early land residents probably produced mucus, Bresman said, and they may have had some kind of adaptation to mucus and survived on the land to prevent lubrication and dryness. I helped.
And Wainwright wants to know if other fish species have unique mucus. It suggests that some fish live in sediments at the bottom of the water.
“No one ever saw mucus diversity with a lens that is very close,” Wainwright says.
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