Beneath the surface of the Mediterranean, a quiet invasion has been unfolding unseen — not because the invaders were absent, but because science lacked the eyes to find them. A new study reveals that what taxonomists long classified as a single marine worm species is in fact eight distinct lineages, four of them invasive newcomers to a sea already burdened by biological intrusion. The discovery is less a surprise than a reckoning: when our categories are too coarse, the world slips through them, and the losses we fail to name are losses we cannot address.