Unlike the famous great white, a sister species to sharks is so mysterious that it was caught on film for the first time only a decade ago.
The “ghost shark” is aptly named for its illusive nature. As it lives at depths of the ocean where light cannot penetrate, amidst crushing pressures, it’s rarely seen, and very little is known about it.
Yet, the name ghost shark, too, is deceiving. The species is not really a shark at all, but belongs to a small sister group to sharks—as do skates and rays. Its proper name is chimaera (chimaeriformes order). Similar to sharks, chimaeras are cartilaginous fish, which means they have no bones but cartilage that keeps their bodies rigid instead.
Chimaeras typically have a triangular dorsal fin and two triangular, pectoral fin-wings on either side. They have been reported to get as long as 4 feet.
Chimaeras are unusual fishes. Like sharks, their bodies are not stiffened by bones, but by plates and bone-like bits of…
Around the world, chimaeras are usually found at depths of between 400 meters and 2,000 meters but are occasionally seen at depths of around 3 meters for mating or laying eggs. This accounts for the chimaera’s obscurity.
“The deep sea is vast and remote, and also a place of extremes—there are near-freezing temperatures, crushing pressures and a complete absence of light,” explains Dr. Diva Amon from the Natural History Museum, via Forbes. “It’s a place we cannot venture easily and this makes it an incredibly difficult place to work.”
The ghost shark was video-recorded in its natural habitat for the first time in 2009. Researchers from the Monterey Bay Aquarium Research Institute (MBARI) lowered a remotely operated vehicle (ROV) off the coast of California. They witnessed what was thought to be a pointy-nosed blue chimaera—a second hypothesis was that this was an entirely new species of ghost shark.
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The chimaera appeared to be quite curious about the ROV.
“It’s almost a little comical,” said Dave Ebert, program director for the Pacific Shark Research Center. “It would come up and bounce its nose off the lens and swim around and come back.”
The researchers believed the specimen matched the features of hydrolagus trolli species but stated in journal Marine Biodiversity Records that genetic samples would have to be collected in order to confirm that hypothesis.
There are believed to be three main families of chimaeras, though they are often lumped together. They are the ploughnose chimaera (callorhinchidae), the shortnose chimaera (chimaeridae), and the longnose chimaera (rhinochimaeridae). And among these, there are thought to be 52 different species of chimaera.
The rare and strange-looking shark relatives have garnered many nicknames besides “ghost shark.” They are also known as “ratfish,” “elephantfish,” “rabbitfish,” “waterbunnies,” and “spookfish.”
Some of their other unusual features, which further set them apart from true sharks, are that they do not have rows upon rows of jagged, razor-sharp teeth, as sharks do. Rather, ghost sharks have tooth plates; a sharp upper plate that is fused to the skull, and a lower, flat plate used to hold its prey in place. They typically hunt crustaceans, worms, mollusks, and bottom dwellers.
Chimaeras also have small dot and channel patterns on their heads, which are believed to be sensory organs that help them find their food.
Even stranger is the fact that (male) chimaeras possess retractable sex organs on the least likely of places: their foreheads.
Strange in a different way is the origins of the name “chimaera,” which alludes to the fantastic, hybrid beast from ancient Greek mythology. Spelled slightly differently, the “chimera” is a fire-breathing animal consisting of a lion with a goat’s head sprouting out of its back with a serpent for a tail.
Similar to sharks, however, chimaeras are animals that are older than the dinosaurs. And yet, despite their prevalence through history, there is so much we do not know about them. It is only with the development of new innovations that we have begun to unveil the mystery of the ghost shark.