A squid's skin is covered in tiny hair cells — and scientists have now mapped them across the animal's entire body for the first time. The discovery could help explain why humans lose their hearing permanently.

The Case Western Reserve University team, led by Brian McDermott, found that squid carry lateral-line-like sensory systems studded with hair bundles, similar to the ones in the human inner ear that detect sound. Using light-sheet microscopy, they charted the full-body map.

The key difference: many animals can regrow damaged hair cells, but humans cannot. Once the hair cells in our ears are destroyed by noise, age or drugs, hearing loss is permanent. Studying how squid build and maintain theirs could point to ways of triggering regeneration in people.

The study was published in Current Biology. Researchers say the humble squid may become an unlikely model for one of medicine's hardest problems. Next, the team wants to test which genes drive hair-cell growth in squid, hoping to find switches that could one day be flipped in humans.

Sources: case.edu; scienmag.com.