Rare shapeshifting whalefish spotted off the coast of California

A remarkably bizarre fish that has confused scientists for centuries has just made a rare appearance at the Monterey Bay Aquarium Research Institute off the California coast.

A one-of-a-kind sea creature

Historically, it has only been seen 18 times over the last three decades of research into the species. The female whalefish that was spotted by researchers, was seen 'half swimming, half gliding' 6,000 feet below the surface, while they used a remote submarine to study the depths of the Pacific Ocean. The Monterey Bay Aquarium Research Institute tweeted:

Whalefish have rarely been seen alive in the deep, so many mysteries remain regarding these remarkable fish. With each deep-sea dive, we uncover more mysteries and solve others.

The first whalefish observed was in 1895 and has since confounded researchers due to its ability to take on different body shapes during its lifetime. Even more interesting, the whalefish will take on completely different body shapes depending on its gender.

The fish in question start their lives as tapetail—the larva stage where the scale-less fish has a long, streamer-like tail and upturned mouth before going through an impressive transformation.

Male vs female transformations

For male tapetails, scales form along its body, their jawbone disappears and a large nose appears at the front. Its esophagus and stomach completely disappear and are instead replaced by a large liver and sex organs. Male whalefish swallow crustaceans alive and whole to keep their body's fuelled throughout their journeys.

Female tapetails, on the other hand, develop a body similar to a baleen whale, which might explain why the species was given its name. Female fishwales come in a range of bright oranges and reds, while males exclusively vary within different shades of orange.