Life under pressure
The blobfish, Psychrolutes marcidus, lives in the deep waters off the coasts of mainland Australia and Tasmania, at depths between 600 and 1,200 meters (about 2,000 to 3,900 feet). Down in this aphotic zone, the pressure is between 60 and 120 times greater than at the surface. Under such immense force, a conventional gas-filled swim bladder, which most surface fish use to control buoyancy, would collapse. The blobfish lacks this organ entirely.
Its primary adaptation to this environment is its body composition. The fish’s flesh is a gelatinous mass with a density slightly less than water. This allows it to achieve near-neutral buoyancy, floating effortlessly just above the sea floor without spending energy on swimming. Its skeleton is made of very soft, flexible bones, and it has minimal muscle, which is not a disadvantage for its lifestyle. This low-energy body plan is ideal for an environment where food is scarce.
The decompression problem
The famous image of the blobfish as a saggy shape comes from severe tissue damage. When a blobfish is hauled up from the deep by fishing trawlers, the rapid change in pressure causes a catastrophic decompression effect. The low-density, gelatinous tissue, which provides the fish's structural support in its high-pressure home, cannot hold its shape at the surface. The body expands, causing its features to distort into the droopy form that won it the title of "World's Ugliest Animal" in a 2013 online poll.
In its natural habitat, the pressure of the water gives the blobfish a more conventional fish-like shape, with a large head and a tapering body. It is a lie-in-wait predator, opening its mouth to consume edible matter that floats by, such as small crustaceans and other invertebrates. This method of feeding requires very little energy, aligning with its low-muscle anatomy. The fish can grow to about 30 cm (12 inches) in length and may live for up to 130 years due to its slow growth and metabolism.