Sea robins, a unique species of fish that inhabit the ocean floor, have been found to use their taste bud-covered legs to sense and unearth prey, according to groundbreaking research. These extraordinary creatures are so proficient at detecting and digging up food as they traverse the seafloor on their six leg-like appendages that they've become a point of interest for other fish species, which often follow them in hopes of scavenging some of the newly exposed prey.

David Kingsley, co-author of two studies published in Current Biology, first encountered these fascinating fish in 2016. Kingsley, a professor in the department of developmental biology at Stanford University, was captivated by their unusual appearance: "The sea robins I saw had the body of a fish, the wings of a bird, and multiple legs like a crab," he remarked. This encounter sparked his interest, leading him and his team to investigate these fish in a laboratory setting.

Their research unveiled a trove of surprises, including the genetic factors behind the sea robins' distinctive traits, such as their leg-like fins that have evolved into sensory organs. The sea robins' unique extremities, extensions of their pectoral fins, have been adapted for walking, as explained by Amy Herbert, a postdoctoral scholar in Kingsley's lab. "We use the term 'legs' due to their remarkable walking function," she clarified, "though they differ structurally and positionally from human legs."

The study's findings highlight the complex adaptations that evolution can produce in specific environments. Sea robins, for instance, have developed the ability to "taste" their prey with their highly sensitive appendages. Corey Allard, the lead author of the study and a postdoctoral fellow at Harvard University, sees these fish as a model to understand the development of new organs.

During their research, the team observed the fish alternating between swimming and walking, and noted their ability to scratch at the sandy surface without any visual cues to locate buried prey. "Remarkably, they were exceptionally good at this, even capable of uncovering ground mussel extract and single amino acids," Nick Bellono, a Harvard professor and co-author, revealed.

An unexpected twist in their research occurred when they discovered that the sea robins they initially studied were of a different species than those they later received. The northern sea robin (Prionotus carolinus) possesses shovel-shaped legs covered in papillae, similar to human taste buds, while the striped sea robin (Prionotus evolans) has rod-shaped legs without papillae and lacks the sensory capabilities.

This discovery led the researchers to hypothesize that the digging behavior and sensory ability of sea robins may have evolved as a novel method for finding food or as an energy-efficient alternative to swimming in certain environments. The regulatory gene tbx3a, which plays a role in limb development across various species, including humans, was found to be crucial for the development of the specialized fins and papillae in digging sea robins.

The research by Kingsley, Herbert, and their colleagues has shed light on the evolutionary mechanisms behind the sea robins' sensory appendages. As they continue their work, they aim to uncover the precise genetic and developmental processes that have led to these remarkable adaptations.