Some sharks "shrug" to eat

When we swallow food, special muscles push it further down the esophagus. And what about sharks who do not have such a tool? And they do not eat cereal for breakfast. Scientists have found that sharks use their shoulders to swallow food. How does this happen?

Marine vacuum cleaner

Researchers came to this unusual conclusion by using sophisticated X-ray film technology to see for the first time that bamboo sharks shook their shoulders while eating. Thus, pulling the “shoulder girdle” back, the sharks create a vacuum, thanks to which food passes through the back of the head into the digestive tract along a long throat.

In the photo: Whale shark with a similar way of eating.

Bamboo sharks (Chiloscyllium plagiosum) belong to a number of species of sharks (and many other fish) that use suction to pull prey, for example, from rocky crevices or from the silt of the seabed. Opening his mouth wide and fast, sometimes using the muscles deep in his body, the fish can create enough movement to allow food to swim into the mouth with this stream.

Further, bamboo sharks use their shoulders, consisting of a U-shaped cartilaginous belt and various attached muscles, for digestion, as well as for controlling the front fins during movement. Previously, scientists did not suspect that the shark girdle plays such an important role in the process of eating. It is not directly connected to the jaws or anything else in the head.

X-ray movie

A unique technology that combines computed tomography of the skeleton with high-speed high-resolution X-ray films helped scientists dispel doubts. Tiny implanted metal markers create an accurate visualization of how bones and muscles move inside animals and humans. During the study, the team used the system to observe three bamboo sharks on pieces of squid and herring. A fraction of a second after closing the mouth, the cartilage of the studied sharks quickly turned back (from head to tail) by about 11 degrees.

Although only bamboo sharks were involved in this study, scientists suspect that other sharks, which suck water for food, move their shoulders in the same way. This study can help scientists answer the question of how the shoulder girdle was formed in sharks and other fish.

In addition, knowing how the skeletal structure of fish evolved could help to better understand how some creatures ultimately managed to get out of the water to land.