Amphibians can sniff underwater

It is believed that amphibian mammals cannot smell when they dive into the water. But an American scientist has discovered that star-nosed mice in North America are capable of sniffing for prey underwater with air bubbles emitted from the mouth.

"For me, this finding is extremely unexpected, because everyone has thought that mammals cannot smell underwater. When mammals move to live in water, their hearing Often amphibious, amphibians - like dolphins and whales - have lost their ability to smell, "said Kenneth Catania, a professor of biology at Vanderbilt University, Nashville, Tennessee, USA.

Catania began tracking the star-shaped mole rat (scientific name Condylura cristata ) after he saw a child blowing a lot of air balloons while swimming. He and his colleagues chose 5 star-nose mice, put them in glass containers with water. Then, they put some soil worms, small fish, bits of beeswax and silicon at the bottom of the cage. Scientists measure the amount of air that mice inhale and exhale through a high-speed camera mounted below the glass cage.

The first thing to notice is that the mice release the bubbles out of their nostrils and swallow them immediately afterwards . "Mice can't swallow all the air bubbles they release, but most of the air has returned to their nostrils , " Catania said.

Condylura cristata - Condylura cristata (Photo: discoverlife)

The air bubbles of a star nose are released and inhaled at a fairly rapid rate - about 10 times a second. This means that the breathing speed of the nose mouse is no less than that of a hamster or some other mammal.

"The way of sniffing hamsters is different from us. They release the bubbles and inhale like a star nose, but on land, not in the water," Catania said.

According to Catania, when the star-nosed mouse approaches a target, they open their mouths to blow the air balloon towards it and use the two inhaled nostrils immediately.

"Because the olfactory neurons of the star nose are covered with mucous membranes, they can smell the smell of dissolved substances. When the bubbles touch the target, it is possible that the molecules smell from. that followed the air into the nose when they inhaled the air bubbles, " Catania explained.

But it doesn't mean that the nose mouse detects the odor molecules under the water doesn't mean they have detected those molecules. This amphibian has a powerful weapon: the star-shaped nose is composed of 22 extremely sensitive and flexible tentacles. Every time they sniff an object, they also touch the surface of the object with tentacles.

To clarify the problem, Catania overlaps the " bait " an iron net to prevent the star nose from reaching its targets. The meshes are too small for tentacles but large enough for air bubbles to pass through.

The nose of a star-shaped mouse has 22 extremely sensitive tentacles.(Photo: newscientist)

The results showed that rats could trace the prey by releasing air bubbles and then inhaling again. At the first attempt, they found the target position with an accuracy of 75% to 100%. After that, the experts replaced a mesh with smaller eyes, meaning there were fewer bubbles going through the net. As expected, the success rate of animals decreased - less than 50%.

To find out if the possibility of underwater sniffing exists in other amphibians, Catania forces some rats to water and conduct a similar experiment. He found that they also sniffed and followed the trail of prey underwater.

"Now we need to find out what other amphibians are capable of. Whether large amphibians like seals and otters can sniff out underwater, or only small species. Catania said , "Can you do that?"

Viet Linh