Meet the Uber-Rare Ghost Shark: Not Quite a Shark, Not Quite a Fish

The Hydrolagus trolli, the pointy-nosed blue chimaera, or “ghost shark,” is unlike any other on earth. Sightings are rare, and this deep-sea creature has only been filmed a handful of times in the Pacific. The eerie appearance of the pointy-nosed blue chimaera was seen up close for the first time in this YouTube video. Its bizarre physical features set it apart from other boneless fish species, making it one of the most unique Chimaeridae in the ocean.

The Rare Nature of the “Ghost Shark”

The pointy-nosed blue chimaera was named for Alaskan artist Ray Troll, who loved the species so much that his artwork immortalized it. However, Troll was not the only one curious about this strange fish. More than a decade after the first specimen was discovered, Monterey Bay Aquarium Research Institute scientists captured it on camera. Before this video, it was believed that the pointy-nosed chimaera lived primarily in the western hemisphere. This live footage challenged this, as it was filmed off the coasts of Hawaii and California.

This added further mystery, as scientists believed the fish was native to the waters off New Caledonia and Australia. Its choice of habitat makes this fish seem less rare than it is. The reason sightings are so infrequent is because of the depth at which it lives. Pointy-nosed chimaeras are deep-sea divers, never swimming above 2,000 feet. This makes it challenging to study them, if not for videos like this one. Through studies of other chimaeras, scientists have determined that they are “living fossils.“

Not Quite a Shark, Not Quite a Fish

The chimaera originated in Greek mythology and was an amalgam of several animals. It’s now a scientific term for “hybrids,” or animals that are not quite one thing or another. Due to their boneless bodies, chimaeras are related to rays, sharks, and skates. They share commonalities with sharks, both descendants of a common ancestor from the Jurassic era. Bone-like pieces of cartilage and flat plates give their bodies shape. This is also what differentiates them from being true sharks. A chimaera’s upper jaw is fused to its skull, while its lower “teeth” consist of grinding tooth plates. It only has four gills, whereas sharks can have up to seven on either side of their bodies.

There are roughly 50 species of chimaera swimming in the deep sea, which can grow up to 6.5 feet in length. The pointy-nosed blue chimaera can grow just over a foot, making it one of the smaller varieties. Like many other deep-sea creatures, the pointy-nosed blue chimaera has large eyes that allow more light. Its blue-grey hue makes it a true “ghost shark,” helping camouflage the fish against the rocky seafloor it prefers. While little is known about the behavior of the chimaera, it’s believed the dots along its forehead are sensory organs. The same is true of the deep grooves in the chimaera’s face, which are sensitive to movement. Both features help the chimaera to hunt prey on the seabed. Their diets consist of mollusks, crustaceans, and marine worms, and their extra perception helps track movement at dark depths, making up for their poor eyesight.

Its Retractable Penis is Rather Practical

Between its wing-like fins and unusual facial features, the pointy-nosed blue chimaera is one of the strangest deep-sea fish out there. Its most bizarre feature is what retracts out of its head: a reproductive organ. The pointy-nosed blue chimaera has a penis that extends and retracts from its head but unfortunately, no one has seen it in action. Scientists can confirm this “ghost shark” species is equipped with retractable genitals because they are essential to all chimaeras.

According to National Geographic, the sex organ of a male chimaera is shaped like a rod with protruding spikes. When a male and female mate, this allows the male to “lock” onto the female. This is one of three grasping organs that help stabilize the fish while mating. When its penis retracts, it fits into an indent on the female’s head, which allows the male to latch on while fertilizing the female’s eggs. Females have a built-in sperm bank lasting several years, making reproduction easier. Since chimaeras are oviparous, they bury egg cases in the sand, and it takes six months to a full year for these eggs to hatch. Scientists can make an educated guess as to how the pointy-nosed blue chimaera reproduces, but believe the process is similar to that of any other chimaera. Analysis of other chimaera species and footage of the pointy-nosed blue chimaera provides a rough picture of the species’ survival.