The Fish that Walks and Tastes with Its ‘Legs’

While we can’t imagine tasting with our legs, for this peculiar fish, this ability is necessary for survival.

Photo byWikimedia commons

Nature is weird, and one such oddity is the sea robin. This fish has fascinated scientists for years with its ability to walk along the seafloor. The sea robin has six leg-like limbs, which are actually modified pectoral fins that it uses to dig up buried prey. However, until recently, researchers weren’t entirely sure how the sea robin was so skilled at finding food.

New research has revealed that the sea robin uses its legs to actually taste the environment. The study was published in Current Biology and shows that these appendages are covered with small bump taste receptors similar to those on a human tongue.

The appendages allow the sea robin to detect chemicals in the sand and locate prey hidden beneath the surface. (“Evolution of novel sensory organs in fish with legs | Current Biology”)

In an experiment conducted by Harvard professor Nicholas Bellono and his colleagues, sea robins were placed in tanks with buried mussels. The fish always dug up the mussels but ignored empty capsules.

The experiment proved that their legs were involved in the detection process. When the researchers added capsules containing mussel extract, the fish continued to dig in those spots, demonstrating that the sea robins’ legs could "taste" their prey even when it was buried. (“This Fish Doesn’t Just Walk—It Tastes With Its Legs, Too | gizmodo.com”)

What’s even more remarkable is that the sea robins didn’t need to physically touch the mussels to detect them. Their legs were so sensitive to chemical signals in the sand that they could sense prey from a distance of up to four inches. This sensory ability is similar to how flies taste with their feet, making the sea robin another example of nature’s strange adaptations.

The research team also discovered that a specific protein, tbx3a, plays a critical role in both the development of the sea robin’s limbs and the taste receptors in the legs. This protein is also involved in limb development in other vertebrates, including humans. In sea robins, however, tbx3a has been repurposed to enhance their ability to sense prey through taste.