Look at the "waste fish" of the southern United States suck its prey

The alligator gar, a fish with a narrow throat and narrow muzzle that resembles the reptile of the same name, is the largest native freshwater predator in North America. They live mainly in Arkansas, Louisiana and Texas and can measure up to 10 feet long and 300 pounds. Long regarded as "discarded fish" by fishermen who often reject them because they are not worth it, the guys occupy a special place in the hearts of biologists who study the evolution of fish.

Charles Darwin called the guys "living fossils" because they have more or less the same body as their Cretaceous ancestors, more than 100 million years ago. Studying modern guys can provide many clues about the life of these ancient fish and their parents. Now, a new study from the University of Chicago reveals fascinating details about how the boy feeds, both by breaking his powerful jaws and, surprisingly, by using a suction to suck his prey to l & # 39; inside.

The research, published in the Journal of morphology, uses high-speed videography to capture images of the gar's jaw while catching prey. Justin Lemberg, a postdoctoral researcher at UChicago who led the study, then applied the measurements taken from the video sequence to a 3D software model of the skull of the gar to reconstruct the movements of his joints and bones.

"Having living things that retain all these ancient features helps us understand what is happening in the fossil record," Lemberg said. "If we can understand what some of these features are for with the modern gar, we may be able to better interpret when these features appear in other fossils."

Overcoming the physics of water

Unlike humans, whose jaws open and close on a simple hinge, fish have complex skulls composed of multiple bones, joints and cartilage that slide, flex and turn to open the jaw and expand the palate. This helps the fish overcome a fundamental physical problem: when they approach the food under the water, their bodies also push a wave of water in front of them. Without compensating for this, it would repel it (think of the difficulty of picking a crumb out of a glass of water without trapping it against the side).

The teleosts, which make up the vast majority of fin fish such as bass or snapper, solve this problem by opening their mouths, widening the palate and parts of the skull at various points to create a suction and suck in the air. water through the gills. . It was thought that the guys were simple "side snappers" that approached their prey and cut their long muzzle to the side while crushing them with their long rows of teeth.

For the study, Lemberg used 17 alligator guys he raised himself after picking them up at a hatchery in Warm Springs, Ga., And bringing them back to Chicago in the back of his Honda Civic.

He then trained the guys to feed on freeze-dried pieces of krill, held under a clamp under intense light, so they could use a special video camera that records at 500 frames per second. Surprisingly, when one of the guys was positioned against the aquarium and could not use his characteristic reduction movement, Lemberg could see the piece of krill that he was about to eat starting to move in his mouth as soon as he opened his mouth. then stay inside because it closes them. This meant that the gar also created an aspiration, just like a largemouth bass. And all that happened in just 42 milliseconds.

"It was completely unexpected to see a boy just open his mouth and see his food fall in like that," Lemberg said.

Lemberg also used a detailed scan of the skull of the gar to reconstruct the movements of all his bones in a 3D software model. He noticed that when he was watching a video showing the top of the skull, he could see flashes of white and unexposed skin showing when the gargar closed his mouth. When he recreated this move in the model, he showed that part of the palace had to slide outward along a single joint called basipterygoide process in order to expand jaws and create suction.

"What that says, it's simply by opening its jaws, which are large flat plates, this creates a negative pressure between the jaws that helps to attract prey," Lemberg said. "Then, when the jaws close, instead of having the potential to repel the prey with the water while it's agglomerating, it expands these posterior elements to pursue that further aspiration." backward."

Show the waiter a little bit of love

The study adds to the relatively thin literature about guys and the mechanics of their diet. Mr Lemberg said the only other study specifically devoted to alfalfa that he had found was published in 1980, and another comparing it to other fish from 2004.

And maybe it's time for the humble man to have a scientific love. In March of this year, the Arkansas legislature voted the Alligator Gar as its state fish after a campaign launched by a 10-year-old boy.

"It is absolutely necessary to have these data, because they can tell us a lot about how old fish were fed on fish," Lemberg said. "Since it was not there, I had to go and get it myself."