They're from Lake Baikal which houses many organisms unique to only that body of water (including a species of freshwater seal).
The water is so cold that debris-eating fungus species can't survive in the lake. These giant amphipods (similar to gammarus species in NA) are the main "cleaners" of dead matter in the lake. I can't ID the species for you. There are over 250 recognized Gammarid amphipod species endemic to Lake Baikal. I don't know enough about them to differentiate between particular species.
As far as I've researched, all Lake Baikal fauna is protected. And, since most of the life in the lake cannot tolerate temperatures more than a few degrees above freezing, I would think they'd be difficult, at best, to maintain in aquaria.