The mental ability to breathe air is rarified in fish , but it does exist . Why , then , do only   two percent of Pisces species develop   a function that has proven so useful for mammalian , birds and reptilian ? concord to one study , it ’s about a want of personality .

Air - respiration can only be done at the piddle ’s surface , which also tends to be where piranha can be discover . “ tune is a rich informant of oxygen but breathe it is risky , so it made me enquire if it might be linked to personality , ” saidDr .   David McKenzieof CNRS Montpellier in astatement .

Studies of animal personality have concentrated on theshy - sheer axis ,   as this appear to excuse the most about animal behavior , although it isfar fromthe whole story . McKenzie reasoned that if fish were deter from do to the surface by vulture , the boldest in species that can breathe air   would make most use of their power .

African sharptooth catfish ( Clarias gariepinus )   can breathe directly from the air or use gills to extract O dissolved in water . C. gariepinusare an invasive species in Brazil , so McKenzie settle to do his second by pick up 29 from São Paulo river .

McKenzie report his finding in a paper published in theJournal of Experimental Biology , incredibly entitle “ To Boldly Gulp . ”   He set aside the catfish to catch one’s breath for 24 hours after being collected and then quiz the ratio of O prevail from air and water .

Researchers then test the personalities of their captives by tapping the tanks and valuate the holdup before they went back to breathing the air . “ We assumed that how chop-chop they returned to zephyr respiration was a mensuration of how bold they were , ” McKenziesaid .

The study tested the fish in water with different levels of dissolved oxygen , include some so rich the catfish did n’t demand to make out to the open at all . Even in amply aerate water , some catfish choose to come to the open , but unsurprisingly they did so much more in dead waters where oxygen levels were low .

There was a strong correlation between a   high metabolism and extra air - breathing , but personality mattered as well . Catfish that returned to the surface within 75 minute of being frightened were likely to breathe more often during day than the unsure I who took more than 115 minutes before resurfacing .

High - metamorphosis Pisces emit more air when placed in oxygen - poor water , but were not more potential to surface than their depressed - metabolism counterparts when dissolved oxygen was useable . On other bridge player , shy Pisces breathe less air during the day , when vulture would be a terror , but were as potential to surface at nighttime as their bluff cousin-german .

While gamey - metabolic process fish were sheer on average , the correlational statistics was not firm enough to make this a bare case of high-pitched metamorphosis forcing personality change . “ Some animals take risk of exposure because they have to , ” McKenziesaid .   “ Others seem to take risks just because they desire to . ”