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Sea Creatures 101: Chimaeras

© Sharon Rorem

I was doing a word search for strange fish, and the word "chimaera" popped up. "That's a fish?" I thought. "I have never heard of it!" I dug a little further. My question was, "What is this fish and why is it strange? What is a chimaera?"

Chimaeras are in the class Chondrichthyans, and the sub-class Holocephali (which means "whole head"). The name chimaera, which means "wildly imaginary" or "absurdly fantastic" probably came from the mix of odd characteristics. They have a head out of proportion to their bodies, big eyes, and a rabbit-like mouth with one pair of teeth in the lower jaw and two pairs in the upper jaw. Their bodies are thick and taper to a long, thin, rat-like tail. They have a dorsal spine that contains a poison. The poison can cause quite a bit of pain but it is not fatal. They have large wing-like fins, and skeletons made of cartilage rather than bone. Male chimaeras have three clasping organs used for mating- two below the pelvic fin and one on top of their head. The two pelvic claspers are used in mating and the clasper on the top of the head is called a cephalic tentaculum. It has an opposable tip (like a hook) which the male uses to catch a female that is willing to mate. The female chimaeras have a hollow area on the back of their heads. That's where the male "hooks up" with her as she swims by. They live in temperate ocean floors. Favorite foods are clams, shrimp, worms, sea stars, and other fish.

There are 35 known species of living chimaeras, divided into three families: Chimaeridae, Rhinochimaeridae, and Callorhinchidae. The Chimaeridae family includes the shortnose chimaeras known as Spotted Ratfish. These are found off the west coast of North America. It can grow to three feet long and will "fly" as it swims, skipping across underwater mud plains. It will swim at depths as shallow as 20 feet. Divers in the areas near Washington and British Columbia will often come across these on their dives. The Spotted Ratfish is quite beautiful to see in the water because its body is silvery-bronze and has white spots. The body, along with the Spotted Ratfish's emerald-colored eyes, reflects the diver's underwater light. The Spotted Ratfish females will "lay" two eggs at a time. These "eggs" are actually leather-like fully enclosed pouches with a baby Spotted Ratfish inside, attached to a yolk sac. The mother drops the "egg" as she swims. This can take 4 to 6 days. Once the "egg" is loose from the mother, it drops to the bottom of the water and usually catches onto a rock or piece of coral. It will stay there until the baby is big enough to break out of the sac and swim on its own.