A team of Japanese researchers has lowered a high-tech camera rig into the depths of the Mariana Trench, the lowest point of the ocean, to capture a snailfish in action at a record-breaking 8,178 m below the surface.

Recent research has pinned 8,200 m (5 mi) as the deepest point an ocean-going fish can swim. It is believed that this is due to a set of competing effects relating to a chemical called trimethylamine N-oxide (TMAO). On one hand, TMAO prevents proteins from collapsing under high pressure, so the more TMAO a fish contains the greater the depths it can survive.

But on the other, greater concentrations of TMAO means more seawater water is drawn in through osmosis. This is fine up to a point, but at greater depths, higher TMAO levels reverse osmosis pressure, causing brain cells to swell and burst.

Fish have previously been filmed swimming at 8,152 m, but now researchers at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) and the Japan Broadcasting Corporation have plumbed the ocean depths even further.

The team used a baited 4K camera trap called a hadal lander to attract deep-sea organisms at depths of 7,498 m and 8,178 m in the Mariana Trench. Using mackerel as bait, the traps initially drew in amphipods at both sites, and at the more shallow installation snailfish followed three hours and 37 minutes later.

It wasn't until 17 hours and 37 minutes after the lander was installed at 8,178 m did a snailfish appear. The researchers believe it to be the same species that popped up at 7,498 m and though it hung around for a while, no other specimens were spotted.

You can see this lone ranger of the deep sea in the video below.


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