A fascinating discovery in marine biology reveals that the northern sea robin, a fish residing on the ocean floor, has evolved unique legs that serve a critical purpose beyond walking. These legs function as advanced sensory organs, akin to a tongue, enabling the fish to locate prey hidden beneath the seabed.
The northern sea robin (Prionotus carolinus) features three legs on each side of its body, emerging from the base of its pectoral fins, derived from fin rays. This adaptation allows them to thrive in their underwater habitat.
During a research expedition in Woods Hole, Massachusetts, scientists observed the remarkable hunting capabilities of sea robins and decided to investigate their efficiency in locating food. Preliminary findings confirmed that these fish excelled in discovering hidden prey, able to uncover capsules containing ground mussel extract and single amino acids, indicating a high level of foraging skill.
However, upon collecting a second batch of sea robins, researchers noted that while the fish demonstrated proficiency in walking, they struggled to detect prey buried in the sand. Further investigation revealed an accidental collection of a different species, the striped sea robin (Prionotus evolans), which primarily hunts visible prey.
Upon comparison, the legs of digging sea robins were markedly different, with distinct sensory papillae that are easily observable. These structures house taste receptors and touch-sensitive neurons, similar to taste buds found in humans.
While various fish species have adapted their pectoral and pelvic fins for activities such as walking or perching, the sea robin stands out due to its ability to move its legs independently and swiftly, enhancing its capabilities for both walking and digging for food.
Research also delved into the genetic mechanics behind the evolution of these specialized legs. It was revealed that the development is governed by the ancient regulatory gene tbx3a, which is crucial across various animal species, ranging from fish to mammals. This discovery exemplifies how evolutionary processes can create new anatomical features by repurposing existing genetic frameworks.
