Chimaera

The chimaera is a unique, cartilaginous fish closely related to sharks, skates, and rays. Not much is known about the lifestyle or reproductive habits of the chimaera, but scientists have identified over 50 chimaera fish species worldwide.

Each family of chimaera fish has a distinctive, somewhat gruesome appearance, and they are often collectively referred to as “ghost sharks” because of their strange, pale coloring.

Classification and Scientific Name

Chimaeras are part of the order Chimaeriformes, which is subdivided into three families:

• Callorhinchidae, meaning “plough-nosed” chimaera
• Chimaeridae, meaning “short-nosed” chimaera
• Rhinochimeridae, meaning “long-nosed” chimaera

The term “chimera” or “chimaera” is also used to describe a mythical lion-goat-snake hybrid creature. While these chimaeras do not bear any resemblance to their Greek mythology counterparts, the name does evoke a feeling of mystery.

Common names for chimaeras include ghost shark, rat fish, and spook fish. These names all stem from the chimaera’s unique appearance.

While the closest modern relatives of the chimaera are the sharks and rays, their last common ancestor lived almost 400 million years ago.

Species

Current knowledge shows that there are about 50 species of chimaera fish that live in the deep ocean. Because so little is known about deep-sea creatures, researchers are constantly updating taxonomic information as new species are discovered.

Some of the best-known species of chimaera include the following:

• Rabbit fish: This species is also known as Chimaera monstrosa. Its name comes from its large head and small, tapering body.
• Pale chimaera: They are sometimes also called the “pale ghost shark” because they have a distinctive whitish-gray coloring that gives them their ghostlike appearance. They are endemic to New Zealand.
• Small-spine spook fish: This unusual creature is part of the long-nosed chimaera family. It is small and pure white, and it has a thin, curved snout that is covered in nerve endings to help it hunt.

Appearance

Chimaeras have a single external gill opening covered by a flap on each side of the body. Sharks and rays do not have this feature, but bony fish do. Male chimaeras, unique among fish, also have tentacles on the forehead and in front of each pelvic fin.

Because there are so many species of chimaeras that live in the deep waters of oceans around the globe, there are many variations of size, shape, coloring, and distinguishing features.

This means that it would be impossible to describe every known species of chimaera. Instead, it would be more useful to look at the average appearance of members of each family of chimaeras.

Plough-nosed

This family of chimaeras is also commonly referred to as “elephant fish.” The family Callorhinchidae includes several living species within the genus Callorhinchus. While they behave similarly to the other members of the chimaera order, they are distinguished by their long, flexible, and fleshy snouts. These “trunks” are used to search the sea bottom for the small invertebrates that they feed on. Their snouts can also sense movement and electrical fields, which makes them better hunters.

The plough-nosed chimaeras typically grow up to four feet long and have flat, elongated bodies. Their coloring is usually a mixture of black and brown patches, and they have distinctively large pectoral fins that help them navigate waters quickly.

Short-nosed

Short-nosed chimaeras are often called “ratfish” because of their long, tapering tails. They can grow to be between one and five feet long, including their tails, and they have a distinctive, venomous spine in front of the dorsal fin that is potent enough to injure a human. Their coloration varies by species, including brown, gray, and spotted patterns.

Long-nosed

Long-nosed chimaeras have long, pointed snouts as well as the long, tapering tails of rat fish. They are typically pale in color and can grow up to 4.5 feet in length. Like the short-nosed chimaera, they also have a small, venomous dorsal spine.

Distribution, Population, and Habitat

Chimaeras can be found in all of the world’s oceans except the Arctic. They typically live between 650 and 8,500 feet below the ocean’s surface. This means that they are considered deep-sea creatures because they reside in the twilight and midnight zones of the ocean.

It is difficult for researchers to gather information about deep-sea dwellers, so much of the information that has been gathered requires further verification.

The majority of chimaera species live near muddy bottoms of underwater ridges, continental shelves, and oceanic islands. This is because they feed on small fish and invertebrates that often burrow into these ocean floors.

The exact population numbers for chimaeras are not known, but they are currently listed as a species of least concern by the IUCN.

Predators and Prey

Chimaeras typically eat crabs, mollusks, sea urchins, marine worms, and small octopuses. They have multiple rows of tough, mineralized tooth plates that allow them to crush their prey.

In general, the main predators for chimaeras are larger fish and sharks. Humans are also a threat to certain species of chimaeras that can be found closer to the surface of the ocean.

In addition, while parasites may not technically be considered predators, scientists have noted that chimaeras are often covered in parasite colonies. One research trip collected nine separate parasite species on a single fish.

Reproduction and Life Span

Unfortunately, little is known about the life span and reproductive habits of chimaeras. However, it is known that males possess external reproductive organs called claspers that inject sperm into the female.

Like some of their skate and shark relatives, chimaeras lay eggs on flat, muddy sea beds. Females lay eggs in pairs, and they can lay multiple pairs during each breeding season. The number of eggs laid depends on the species, and researchers believe that it takes anywhere from 6 to 12 months for the eggs to hatch.

Chimaera hatchlings are usually about 5 inches long, and they look like miniature versions of their adult counterparts. Most deep-sea fish have little interaction with their young because they grow and develop in a shallower stratum of the ocean, so there is almost no overlap in their habitats.

Researchers do not know what the average life span is of a chimaera in the wild, but they have been known to live up to 30 years.

Fishing and Cooking

Chimaeras are edible, but they are not a common food source for humans. Like many fish, they have parasite colonies that live on their skin and in their gills. The rabbit fish, in particular, is thought of as a novelty seafood dish, and some people will also eat ghost fish alongside mussels, clams, or shrimp. In the past, chimaera liver oil was valuable as a lubricant for guns and certain instruments.

Most chimaeras are not actively sought by fishermen because they live in deep waters, but they may be what is known as a “bycatch,” which means that they are caught alongside other targeted species.

Population

The current population numbers for the chimaera are not known. Chimaeras in general are poorly understood by scientists, and there is a lack of useful, up-to-date information on their biology, habits, and numbers.