Beneath the rolling hills of the Ozark Plateau, a vast and silent wilderness exists in total darkness. This is a realm of karst—a landscape shaped by the slow, acidic dissolution of limestone and dolomite, creating a labyrinth of sinkholes, losing streams, and sprawling cavern systems. In these flooded subterranean galleries, life has taken a turn toward the ethereal. Among the most specialized inhabitants of this hidden world is the Ozark cavefish (Amblyopsis rosae), a small, translucent vertebrate that has spent millennia evolving to thrive where the sun never reaches. Recent breakthroughs in environmental DNA (eDNA) monitoring and population mapping have begun to shed light on this elusive species, revealing that its subterranean domain is far more interconnected—and far more fragile—than previously understood. The Biology of Absolute Darkness The Ozark cavefish is a masterclass in evolutionary reductionism. Reachin...