A star for a nose
The star-nosed mole, Condylura cristata, lives in the wetlands and marshes of eastern North America, including parts of Tennessee. This small, semi-aquatic mammal navigates its dark, subterranean world using a unique sensory organ: a star-shaped structure at the end of its snout. This "star" consists of 22 fleshy, pink appendages, often called rays or tentacles, that are in constant motion as the mole explores its environment. Functionally blind, the mole uses this apparatus to build a picture of its surroundings through the sense of touch.
The surface of the star is covered with more than 25,000 microscopic sensory receptors known as Eimer's organs, named for the German zoologist Theodor Eimer who first described them in 1871. Each of these dome-like papillae, about 30 to 50 micrometers in diameter, contains a collection of nerve endings that detect fine textures and shapes. In total, the star sends information to the brain through more than 100,000 nerve fibers—five times the number found in the human hand. This dense network of sensors makes the star a highly sensitive known touch organs in the animal kingdom.
A brain built for touch
The star-nosed mole’s brain is uniquely adapted to process the massive influx of sensory data from its nose. A disproportionately large section of its cerebral cortex is dedicated to interpreting signals from the star. In brain scans, the representation of the 22 rays appears as a series of distinct stripes, mirroring the physical structure of the nose. The mole has a "tactile fovea," a specific pair of rays (the 11th pair) that it uses for the most detailed examination of objects, similar to how humans use the center of the retina for sharp vision.
This specialization allows for incredible speed. The mole can identify and eat a piece of food in as little as 120 milliseconds. Its brain takes only about eight milliseconds to decide if an object is edible. This rapid processing makes it the fastest-eating mammal recorded. The mole forages by constantly touching its star to the ground, contacting up to 10 distinct spots per second. Its diet consists mainly of earthworms and aquatic insects, but also includes snails, crayfish, and even small fish.