Fish Depth Limit Set By ‘Fishy’ Molecule

Scientists say it is unlikely that any fish can survive in the oceans deeper than about 8,200 metres.

No fish has ever been seen living beyond this limit, but the researchers point to good physiological reasons why it should not be possible, also.

It rests on the particular molecular mechanism they use in their tissues to withstand crushing pressures.

To go deeper would require fish to evolve some other mechanism, the team tells the journal PNAS.

The all-important molecule is a so-called osmolyte called trimethylamine N-oxide (TMAO). It is what gives fish their “fishy smell”.

TMAO acts to stabilize the proteins fish use to build and maintain their cells.

Without its presence, the proteins would be distorted by the high pressures found at depth and stop functioning.

The team had observed that fish species appeared to have increasing amounts of TMAO the deeper they went, and sought to test this relationship on hadal snailfish recovered from the bottom of the Kermedec Trench north of New Zealand.

This pinkish animal operates more than 7,000m down, preying upon small crustaceans that eat organic matter that rains from above.

One other type of fish has purportedly been trawled from deeper, but nothing has actually been observed swimming so far down.

“This is by far the deepest fish we’ve caught and analysed, and they have the highest levels of this TMAO molecule,” said lead author Prof Paul Yancey from Whitman College, Washington State, USA.

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Source: www.bbc.co.uk/news