Saccopharynx ampullaceus

[3][4] These fish are rarely observed, so little information is currently known about their habits or full distribution.

In the fall of 1826, a Captain Sawyer, of the ship Harmony, of Hull, while cruising for northern bottlenose whales at 62° N and about 57° W, found the type specimen, floating at the surface, of what was named Ophiognathus ampullaceus by I. Harwood, at the time the professor of natural history at the Royal Institution of Great Britain.

It was at first thought to be an inflated seal skin, but on getting closer they realized it was alive.

Saccopharynx ampullaceus lacks a traditional gas-filled swim bladder, presumably due to the pressures at the depths they live in.

Instead, the function of the swim bladder has been replaced by lymphatic spaces that run along the spine which are filled with a gelatinous substance.