Why are exposed neuromast cells useful to deep-sea protacanthopterygian fishes?

In deep-sea protacanthopterygian fishes, the lateral line system serves as a vital sensory mechanism for detecting water movement and pressure changes. While many fishes possess neuromasts embedded within canals to shield them from the constant stimulation caused by swimming, deep-sea species that live in the absence of sunlight face different environmental pressures.123

For these deep-sea fishes, exposed neuromast cells—often arranged on raised papillae—are useful because they significantly increase the sensitivity of the sensory system. By positioning these receptors on the surface rather than within canals, the fish can better perceive their environment, effectively compensating for the lack of vision in the deep-sea habitat. This heightened sensitivity allows them to more accurately detect the presence of prey, predators, or other objects in the water by sensing minute displacements that might otherwise go unnoticed.213