Pseudoliparis swirei, the Mariana snailfish or Mariana hadal snailfish, is a species of snailfish found at hadal depths in the Mariana Trench in the western Pacific Ocean.[2][3][4][5] It is known from a depth range of 6,198–8,076 m (20,335–26,496 ft),[6] including a capture at 7,966 m (26,135 ft), which is possibly the record for a fish caught on the seafloor.[1][2] Various anatomical, physiological, molecular and genetic adaptions help this species survive in such depths.[5][7]
This pale, tadpole-like fish reaches up to 28.8 cm (11.3 in) in standard length and 160 g (0.35 lb) in weight.[8] It is apparently the top predator along certain stretches of the Mariana Trench, feeding on tiny crustaceans in a deep-water habitat with few larger predators.[4]Pseudoliparis swirei are abundant in their deep-sea habitat and lay relatively large eggs that are almost 1 cm (0.4 in) in diameter.[2]