Sea robins are an unusual type of fish that live on the bottoms of tropical and temperate seas around the world. They mostly eat mussels and other shellfish buried in the sand of these sea bottoms. What makes them unusual is that a pair of fins on their underside has been modified into six legs that look a bit like the legs of a crab. Sea robins “walk” along the seafloor on these legs as they search for their prey. Biologists are studying these animals to learn how their unique appendages evolved and what functions they perform. In twenty twenty four, an international team of researchers published new results.

The researchers found that sea robin legs are covered with sensitive touch and, in some species, taste receptors, while humans only have taste receptors on their tongue. These receptors are sensitive to chemicals dissolved in saliva. It’s entirely typical for fish, unlike humans, to have taste receptors on the outside of their body and even on their tail.

What was special about some species of sea robins was that their legs, like our tongue, had become highly effective sense organs. The researchers showed that the legs help the fish detect chemical traces of their prey as they use them to dig in the sand of the sea bottom. They found what might be important clues to broader patterns in animal evolution. They discovered that the evolution of sea robin legs involved some of the same genes involved in the evolution of our limbs, and that some of the same genes are involved in the development of their taste receptors as in ours.

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Sources

These fish use legs to taste the seafloor, ScienceDaily.com

Sea robins use leg-like fins to taste and navigate seafloor, researchers discover, Phys.org

Sea robins are fish with ‘the wings of a bird and multiple legs like a crab’, CNNScience.com

This fishes legs were made for walking and tasting the seafloor, Nature

‘Crazy little fish have lots to tell us’: Sea robins use legs to taste way to prey, The Guardian

Corey, et al. 2024 Evolution of novel sensory organs in fish with legs, Current Biology, DOI: 10.1016/j.cub.2024.08.014.

Herbert, et al 2024, Ancient developmental genes underlie evolutionary novelties in walking fish, Current Biology, DOI: 10.1016/j.cub.2024.08.042.