Lateral Line

This gray angel exhibits a distinct lateral line but the lines are hard to see in some fishes.

LATERAL LINE (lat-er-uhl lahyn)  A series of tube-like canals  and sensory cells along the heads and sides of fishes by which they are able detect vibrations in the surrounding water.

Lateral lines almost certainly play roles in schooling behavior, predator detection and fishes’ turning away when they sense over-anxious photographers like me swinging their cameras toward them to shoot photos.