Do you know that the sharks do not have tongues?
Yes, sharks do not have tongues. Most cartoons portray sharks as animals having a tongue, but in reality that is not true. Sharks do not have tongues. So, the question arises, how do sharks swallow their food?
Scientists have been carrying out experiments since a long while in order to find answers. And through a recent study conducted at the Browns University, they might have just succeeded.
The observations from their experiments have led them to conclude that sharks ‘shrug’ their shoulders in order to swallow food. This study was successful only due to the X-ray movie technology developed recently. It allows scientists to internally observe mammals and even humans!
Thus, they were able to observe bamboo swing their shoulders internally in order to eat. Sharks are apex predators. Sharks mainly feed on fish, crustaceans, mollusks, plankton, krill, marine mammals and even other sharks. Sharks also have a very strong sense of smell that allows them to detect blood in the water from miles away.
Sharks have skeletons that are primarily made of cartilage. They create suction, by pulling their shoulder girdle back, to draw the food through the back of their mouth into the digestive tract.
The research was carried out by a team led by Ariel Camp, a postdoctoral researcher at Browns University and lead author of the research published in Proceedings B, a Royal Society journal.
“They have this long pharynx, and they have to keep food moving down it,” Camp said. “We think this is part of a ‘hydrodynamic tongue.’ Sharks and fishes that don’t have a tongue control the motion of fluid within their mouths to manipulate food.” However, we now know that the sharks do not have tongues.
X-ray technology behind the success
The X-ray movie technology was created by Camp and her colleagues at the Browns University. They named the technology as the X-ray Reconstruction of Moving Morphology (XROMM). It combines CT scans of the skeleton with high speed, high resolution movies. It consists of tiny metal markers, used to create precise mapping of the movement of the bones and muscles within the body of animals and humans under observation.
It is interesting to know that the sharks that mostly remain near the ocean floor, bottom-feed. Other sharks generally filter feed on tiny fishes. They swim through the ocean, with an open mouth, carefully filtering the planktons.
Camp stated that bamboo sharks are just one among the many species of sharks that use suction to swallow their prey.
Earlier, many scientists had conflicting views on sharks using their shoulder girdles for suction-feeding. This was mainly because there is no actual connection between the shoulders to the jaws or anything else in the head. However, with the invention and development of the XROMM, scientists could see the inside of the sharks as they fed, and measure the swing of the shoulder girdle as well. It was observed that the cartilage rotated backwards at about 11 degrees.
More questions to be answered…
This study involved only the bamboo sharks. However, Camp said she suspects that other species of sharks too, feed in a similar manner. Through further research into this field, she hopes to find a reasonable theory on how the shoulder girdle evolved in sharks.
This could help explain how certain animals evolved to eventually survive on land.
Camp studied some of the fossil records dating years back, and noted that the girdle shows up in the records around the time that their jaws evolved. However, she still cannot figure out what structures the girdle evolved from or how that evolution took place.
She says that part of understanding history, is in understanding what functions the particular structure had to carry out.
Some of the other scientists who played a major role in this breakthrough finding are Cheryl Wilga of the University of Alaska, Bradley Scott of the University of Illinois and Elizabeth Brainerd of Brown University.
The research that discovered the fact that the sharks do not have tongues was funded by The National Science Foundation and the University of Alaska at Anchorage.