Mariana snailfish
A deep-sea fish from the Mariana Trench with transparent skin and large eggs.
The Mariana snailfish lives in the deepest parts of the western Pacific Ocean. It survives extreme pressure through unique physical changes like soft bones and clear skin.
- Maximum recorded length is 28.8 centimetres.
- Found at depths up to 8,076 metres.
- Transparent skin lacks any pigment.
- Eggs measure up to 9.4 millimetres wide.
- Named after Herbert Swire, author of The Voyage of the Challenger.
What it is
This pale fish resembles a tadpole and reaches a maximum length of 28.8 centimetres. Its body weighs no more than 160 grams. The creature possesses transparent skin without pigment. Its bones show incomplete ossification, particularly in the skull area. Muscles are notably thin compared to shallow-water relatives. These features help it endure crushing water pressure. The species lacks functional eyesight due to its dark environment. Large organs and eggs compensate for other structural reductions.
Where it lives
The species inhabits the Mariana Trench within the western Pacific Ocean. Records place individuals at depths ranging from 6,198 to 8,076 metres. One specimen was captured at 7,966 metres on the seafloor. This depth likely represents a record for fish caught directly from the bottom. The theoretical limit for fish survival appears to be around 8,500 metres. Other contenders for depth records may have been caught differently or in open water.
How it lives
These fish act as top predators in their specific stretches of the trench. They feed primarily on tiny crustaceans available in the habitat. Larger predators are scarce in this deep-water zone. The population remains abundant despite the harsh conditions. Scientists use special traps to catch them without damage during ascent. Mackerel serves as bait for these collection efforts. Traditional trawl methods often yield poor results for such specimens.
Breeding and life cycle
Female specimens carry unusually large mature eggs. Each egg can measure up to 9.4 millimetres in diameter. A single female holds up to 23 mature eggs simultaneously. These alternate with roughly 850 smaller immature eggs. Intermediate-sized eggs are rarely observed. No embryonic structures appear inside the largest eggs. Larvae likely spend time in shallower open waters below 1,000 metres before descending.
Fish and people
The first specimens were collected in November 2014 by the research vessel Falkor. Thirty-five additional individuals were caught within ten days. Another specimen appeared in January 2017 aboard the Shinyo-maru. The holotype is an immature specimen caught in late November 2014. Conservation status remains data deficient due to limited study. The species faces no direct human threats in its remote habitat.
Status and threats
Information on conservation is insufficient for classification. The International Union for Conservation of Nature lists this taxon as data deficient. Research relies on rare expeditions using specialized equipment. Deep-sea traps minimize harm during recovery. Standard fishing gear cannot reach these depths effectively. Climate change impacts on hadal zones remain largely unmeasured.
Questions people ask about Mariana snailfish
How deep does the Mariana snailfish live?
It inhabits the Mariana Trench at depths between 6,198 and 8,076 metres. One individual was captured at 7,966 metres on the seafloor.
What does this fish look like?
It is pale and tadpole-shaped with transparent skin. Bones are not fully hardened, and muscles are thin. Eyes appear non-functional due to the perpetual darkness.
What do Mariana snailfish eat?
They feed on tiny crustaceans found in their deep-water habitat. They serve as top predators in certain stretches of the trench where larger predators are absent.
Why is it called Pseudoliparis swirei?
The name honours Herbert Swire, First Navigating Sub-Lieutenant of HMS Challenger. He authored a narrative about the historic 1872-1876 global circumnavigation expedition.
Good reading and sources
- Pseudoliparis swirei on WikipediaEncyclopedia
- More photos on Wikimedia CommonsPhotos
- Wikidata recordOpen data
The facts on this page come from the Wikipedia article "Pseudoliparis swirei", written by its contributors and used under the CC BY-SA 4.0 licence, and from its Wikidata record (CC0). EveryFish rewrote the text in its own words, with AI assistance, and compares every page with the article to make sure no passage is copied. It may be reused under the same CC BY-SA 4.0 licence with a link back.
It may contain mistakes, and figures change over time. Nothing here is investment or buying advice. If something is wrong, tell us. Last refreshed 2026-11-15.
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