Sea catfish is 'a swimming pH meter'

The Japanese sea catfish (Plotosus japonicas) can locate its prey by detecting small changes in the pH of the water.

Animals incorporate a number of unique methods for detecting prey, but for the Japanese sea catfish, it is especially tricky given the dark murky waters where it resides.

Scientists from Louisiana State University in the US and colleagues from Kagoshima University in Japan have identified that these fish are equipped with sensors that can locate prey by detecting slight changes in the water’s pH level, due to the respiration of small sea worms, which are a primary prey of the catfish.

The sea worms live in tubes or burrows in the mud. As the worms breathe, they release tiny amounts of carbon dioxide and acid, producing a slight decrease in the pH of the seawater that the nocturnal sea catfish detects.

"These fish are like swimming pH meters. They are just as good as a commercial pH meter in the lab," said John Caprio of LSU.

This is the first report of any fish using pH to find live prey.

For more information, see the paper: Marine teleost locates live prey through pH sensing, detailing the work of Caprio and his research partners, published in the journal Science.

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