Neat, the wiki for that fish:

https://en.wikipedia.org/wiki/Pseudoliparis_swirei

> Compared to shallow-water snailfish, Pseudoliparis swirei has several unusual adaptions for its dark and high pressure habitat, including transparent skin that lacks pigment, certain organs and eggs that are enlarged, the muscles are thinner, the ossification of its bones (notably the skull) is incomplete, it appears to have little or no ability to see, there are mechanisms that allow proteins in its body to still function, and differences in the cell membranes for maintaining their flexibility.

Very cool. the wiki for that other fish, the shallow water snailfish, Amblystomopsis.

According to Wikipedia, the Pseudoliparis amblystomopsis is a species of fish that belongs to the family Liparidae. Here are some key facts about the shallow water snailfish:

The shallow water snailfish is found in the Pacific Ocean, specifically in the Kuril-Kamchatka Trench, which is one of the deepest parts of the ocean.

Despite its name, the shallow water snailfish is actually adapted to live at extreme depths, with individuals having been found at depths of up to 7,500 meters (24,600 feet).

The shallow water snailfish is a small fish, typically measuring between 12 and 15 centimeters (4.7 to 5.9 inches) in length.

This fish has a soft, gelatinous body and lacks a swim bladder, which helps it to survive at high pressures in the deep sea.

The shallow water snailfish is a predator, feeding on small crustaceans and other fish that live in the deep ocean.

Because of its extreme depth range and unique adaptations, the shallow water snailfish has attracted the interest of researchers studying deep sea biology and physiology.

An interesting case of evolution. In theory the first populations to become fixed for an allele or allelic combination that results in even a small increase in TMAO would be able to access previously untouched feeding grounds and flourish for some time.

Probably also avoid predators, since they seem to be pretty much by themselves down there.

Fun fact: the (in)famous Icelandic "rotted shark" (hákarl) food is rotted/fermented in order to remove the toxic TMAO (and urea):

https://en.wikipedia.org/wiki/H%C3%A1karl

>Chef Anthony Bourdain described fermented shark as "the single worst, most disgusting and terrible tasting thing" he had ever eaten.[2]

Ok that’s saying something.

I tried a ~1x1cm cube of it when I was in Iceland... that assessment is pretty spot-on.

Did you keep it down? The pictures alone make it look very unappetizing, but I have to assume there is a significant aroma to the dish as well.

I also tried it. The smell was absolutely horrible, but compared to that, the taste was not too bad.

So what’s natto’s excuse?

Is this why they expect this fish is near the depth limit? Does this mechanism stop working at higher pressures?

Yeah, the cited depth limit of ~8.5km appears to be based on “fish use an osmolyte called TMAO to protect their proteins from pressure, and below 8.5km the concentration of TMAO required is so high that it inhibits cell function”. Apparently crustaceans get deeper by using five different osmolytes at once instead of relying on TMAO. (Info from helpful comment by mytailorisrich in this thread https://news.ycombinator.com/item?id=35403838)

So in theory fish could adapt to life at greater depths by “learning” to produce more than one osmolyte.