Japanese catfish find their victims on breathing
In the course of evolution, fish have mastered many unusual ways to navigate and find food under water. Their senses are often very different from the inhabitants of the land. For example, using the sideline they feel the vibrations of the water, and their nostrils are, as a hydrochemical laboratory, determining the content of dissolved substances. American scientists have discovered in a small catfish inhabiting the coasts of Japan, another unusual mechanism. These fish are looking for the burrows of marine worms to change the acidity of the water.
Kind prihvataju striped catfish Plotosus japonicas was opened in the southern part of the sea of Japan only in 2008. John Caprio (Caprio John ) and his colleagues from the University of Louisiana several years studying these fish in a specially-equipped aquariums.
Infrared shooting their hunting researchers showed that even in the dark catfish easily detect the tunnels, digging in the sand polychaete worms. The fish have never been interested in empty holes. Caprio suggested that the catfish can detect the smell of any chemicals that excretes a worm, such as amino acids. To test this, the researchers worked on the sensitive whiskers of catfish to various substances. They planned such obrazovanii which ones will cause the hunting interest of the fish.
But instead of the expected result, the team found that the fish reacted not to the substances themselves, and the slight changes in water acidity. This indicator is called pH and is measured on a scale where 0 is most acidic, 7 neutral, and 14 denotes a concentrated solution of alkali. the pH of seawater usually ranges between 8,1 and 8,2. The experiments showed that changing the indicator is 0.1 immediately caused som seizure activity.
The secret lies in the fact that, like many other organisms, earthworms during respiration produce carbon dioxide, which upon contact with water converted to carbon dioxide and slightly acidify the environment. Of course, on open water, these changes are too minor and transient. But the measurements showed that at the entrance to the burrow intense breathing worm really changes the pH to the same value of 0.1.
To prove that in search of food fish are guided by changes in acidity, Caprio introduced a weak acid in an empty hole. As a result of the soma has actively responded to such a dummy and was trying to find worms where they were not.
Scientists pay attention to the fact that according to their observations the fish had ceased to feel the changes of acidity when the water pH fell below 8. Recently there has been a tendency to oxidation of the oceans. but after overcoming this threshold, the soma will not be able to use their unusual abilities for hunting, and thus their population either evolves or becomes extinct.