Northern Sea Robins Use Their Legs To Walk And "Taste" The Ocean Floor For Buried Prey

The sea robin is a bottom-dwelling fish uniquely adapted to life on the ocean floor. These fascinating creatures have frog-like eyes, wing-like fins, and six crab-like legs. Scientists have now discovered that at least one species, the northern sea robin, uses these legs both for walking and for "tasting" the sea floor for buried prey.

Northern sea robins are native to the Western Atlantic Ocean. They can be found from Nova Scotia to the Florida Keys and into the Gulf of Mexico. David Kingsley, a biologist at Stanford University, first caught sight of the unique fish at a small public aquarium in Woods Hole, Massachusetts.

“The sea robins on display completely spun my head around because they had the body of a fish, the wings of a bird, and multiple legs like a crab,” Kingsley told CNN in an email. "I’d never seen a fish that looked like it was made of body parts from many different types of animals."

Eager to learn more about this unusual fish, Kingsley teamed up with scientists at Harvard University. He brought some sea robin specimens from the aquarium to Harvard Professor Nicholas Bellono's laboratory for a closer look. The team discovered that the fish's "legs" are actually extensions of its pectoral fins. However, unlike other fish with similar fin extensions, sea robins can move each leg independently. This makes these fish more adept at walking and digging across the ocean floor.

In previous studies, researchers noticed that other fish tend to follow sea robins due to their ability to find buried prey. The researchers tested this by putting shellfish under the sand in the laboratory aquarium. Sure enough, the sea robins found the food using only their legs. Further investigation revealed that these legs contain sensory organs similar to those found on the human tongue. They allow sea robins to “taste” the ocean floor as they walk around and find prey hidden below.

However, not all sea robins share this unique ability. During their experiments, the researchers accidentally received a shipment of striped sea robins, another species found in the Western Atlantic Ocean. Although the two species look similar, the striped sea robins did not dig or find buried prey. A closer look revealed that these fish did not have taste organs on their legs.

"We were originally struck by the legs that are shared by all sea robins and make them different from most other fish," Kingsley says. "We were surprised to see how much sea robins differ from each other in sensory structures found on the legs."

The scientists shared their findings in two studies published in Current Biology on October 7, 2024. They suggest that since only a few sea robin species have taste organs, the fish's legs initially evolved for movement. Later, certain species developed the additional ability to use these limbs to find food.

Resources: CNN.com, sciencenews.org, Harvard.edu