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The star-nosed mole possesses a truly extraordinary sensory apparatus that allows it to navigate its dark, subterranean world and hunt with unparalleled efficiency. The star-like ring of 22 fleshy tentacles around its nostrils is not merely for show; it is an incredibly sophisticated touch organ. These appendages are densely packed with over 25,000 minute sensory receptors called Eimer's organs, giving the mole the most sensitive sense of touch of any known mammal. To put this into perspective, its star, which is roughly the size of a human fingertip, contains six times more sensory neurons than an entire human hand.
The function of these Eimer's organs is crucial for the mole's survival. As the mole explores its environment, it rapidly touches objects and tunnel walls with its star, much like humans shift their eyes to build a visual image of their surroundings. When a potential food item is detected, the mole uses two particularly sensitive central rays, acting like a tactile fovea, to "zoom in" and confirm if the item is edible. This entire process, from initial touch to ingestion, occurs with astonishing speed, often in as little as 120 to 227 milliseconds, making it the fastest-eating mammal. Its brain can decide if prey is edible in approximately eight milliseconds.
This remarkable speed and sensitivity are vital adaptations for the star-nosed mole, especially considering its poor eyesight and its wetland habitat, which is rich in small prey like worms, grubs, and aquatic insects. The evolution of this unique sensory system is thought to be a response to this environment, allowing the mole to exploit abundant but tiny food sources more efficiently than competitors. Beyond its rapid eating, the star-nosed mole also exhibits another fascinating adaptation: the ability to smell underwater. It achieves this by exhaling air bubbles onto objects or scent trails and then quickly re-inhaling those bubbles to carry scents back through its nose, a feat known only to one other mammal.
The scientific understanding of the star-nosed mole's star has evolved over time. Eimer's organs themselves were first described in the European mole in 1872 by German zoologist Theodor Eimer, though they are far more specialized and numerous in the star-nosed mole. Early hypotheses about the star's function included detecting electrical activity in prey, but extensive research, particularly by neurobiologist Kenneth Catania, has firmly established it as an extraordinary touch organ. Studies have shown parallels between the organization of the mole's somatosensory system and the visual systems of other mammals, with the tactile fovea having a magnified representation in its brain's neocortex, highlighting the star's critical role in its sensory world.