Ghost Shark: Chimaera

Chimaeras are cartilaginous fish in the order Chimaeriformes, known informally as ghost sharks, rat fish, spookfish, or rabbit fish.

At one time a "diverse and abundant" group (based on the fossil record), their closest living relatives are sharks and rays, though their last common ancestor with them lived nearly 400 million years ago. Today, they are largely confined to deep water.

They have elongated, soft bodies, with a bulky head and a single gill-opening.

Their skin is smooth and naked, lacking placoid scales (except in the claspers), and their color can range from black to brownish gray.

For defense, most chimaeras have a venomous spine in front of the dorsal fin.

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Credit: Linda Snook

Spotted ratfish (Hydrolagus colliei) observed off Pt Pinos during a sanctuary seafloor monitoring survey using the Delta submersible.

They also differ from sharks in that their upper jaws are fused with their skulls and they have separate anal and urogenital openings. They lack sharks' many sharp and replaceable teeth, having instead just three pairs of large permanent grinding tooth plates.

Source / Image Courtesy

NOAA

A deep-sea chimaera seen by the Little Hercules in the Sulawesi Sea as part of the NOAA Okeanos Explorer Program.

Its snout is covered with tiny pores capable of detecting perturbations in electrical fields generated by living organisms.

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A longnose chimaera enchants scientists when it swims into the ROV camera view.

They also use electroreception to find their prey.