Marine Life

The electric ray is one of those creatures that might have simultaneously fascinated and frightened you as a child. Lurking unseen on the seafloor, it has the power to send a jolt of painful electricity rippling through your body. The mechanism that provides this power is unique, emanating from kidney-shaped organs made of striated muscle located on either side of the ray’s head. These modified muscles contain columns of electrocytes — jelly-filled electric plates, kind of like rows of batteries — that electric rays use to generate their charge.

Noam Kortler

The Pacific electric ray is found off the coast of California.

NHPA/Photoshot/Superstock

The Atlantic’s beautiful common torpedo ray belies its pedestrian name.

There are many varieties of the electric ray. In the United States, one common type is the Pacific electric ray, found off the California coast. These rays are part of the Torpedinidae family, commonly called torpedoes — which is where we got the name for the weapon — that includes 22 species around the world. The Pacific electric ray can grow fairly large, about 4 feet long, and generates about 45 volts of electricity, which it uses for self-defense and to stun its prey.

The Pacific electric ray’s cousin on the East Coast is called the Atlantic torpedo, and it’s even larger, growing up to 6 feet long and nearly 200 pounds. These behemoth blasters pack the largest punch of any electric ray, producing up to 220 volts of electricity.

The Atlantic torpedoes can be found in coastal waters on both sides of the Atlantic, though they prefer cooler water so are more often seen in locations such as New England and the Mediterranean Sea.

There’s a second family of electric rays called Narcinidae; the main difference between the two is how they give birth, not how they deliver their electrical payload. The name Narcinidae — and its common name, numbfish — comes from the ancient Greeks, who used the rays as a form of anesthesia because of the localized numbing sensation that their shock left behind.

Numbfish are found all over the world; they are not only smaller than the torpedoes — only about 2 feet at the largest — but they also deliver a lesser jolt, ranging from 10 to 35 volts.

The habitat of one type of numbfish — the bullseye electric ray — overlaps with the Pacific electric ray, but you’re more likely to spot the bullseye in the Sea of Cortez than Southern California. It’s easy to spot if you do come across one, thanks to the noticeable eyespot marking it has at the center of its body.

Kevin Raskoff

Nanomia bijuga belongs to a group of colonial animals called physonect siphonophores that are related to jellyfish, anemones and corals.

If you’ve dived the open ocean off Hawaii or Tahiti at night, you’ve probably seen it: a glowing, segmented line that appears to be a single animal but really is many animals working together, collectively known as siphonophores. Now scientists are going beyond the startling beauty of these “multi-engine organizations” and investigating whether their unique method of propulsion could change how we design undersea craft for future generations.

“We can perhaps peer into our own future in the sea,” says marine biologist Jack Costello of Providence College, one of the researchers, “by studying how this seemingly simple animal jets from one part of the ocean to another, relying on its youngest crew members.” (Star Trek fans, score one for Mr. Chekov.)

Lots of marine animals move by jet propulsion — squid and jellyfish spring to mind— but siphonophores are uncommon in that they represent an entire colony that is coordinating individual jets to move the collective as a whole, something like the way each crew member aboard the Starship Enterprise has a specific role in guiding the ship.

Kevin Raskoff

A nectophore budding zone is where a siphonophore’s swimming areas are made.

In a study published in the journal Nature Communications, Costello and colleagues from Roger Williams University in Rhode Island, the University of South Florida, Stanford University and the University of Oregon examined a siphonophore known as Nanomia bijuga. The group of researchers found that younger and older colony members fulfill distinctly different functions.

Costello explains that younger, weaker members, located at the front of the organism, are responsible for turning and steering. Older — and larger — members at the rear provide more thrust. “It’s a sophisticated design in what would initially seem like a simple organism,” Costello says.

The findings suggest it might be possible to design an undersea vehicle that, like N. bijuga, twirls as it moves, propelled by front-to-back thrusters, “a natural solution to multi-engine organization that might contribute to the expanding field of underwater-distributed propulsion-vehicle design,” the study concludes.