Oct 17 2009
Fun Science Fact: This Sixth Sense is Indeed Fishy
A couple months ago I read of research into what was billed as a sixth sense. You can’t call it seeing, nor smell. It’s not quite touch nor hearing. Taste? No. What is it?
Fish and some amphibians possess a unique sensory capability in the so-called lateral-line system. It allows them, in effect, to “touch” objects in their surroundings without direct physical contact or to “see” in the dark. [source]
Is this sixth sense in any way similar to “touch” or “sight”? Hmm. If you ask me, it is a lot closer to hearing. Fish, of course, don’t have ears. But, oddly, many make noises, so they can perceive these. How? It seems that while they lack outer ears, they do have an inner ear structure. Vibrations pass through their body to the inner ear, which allows them to hear. Just as you can hear strong vibrations even with fingers jammed in your ears.
A major difference is that land animals hear vibrations that pass through a gas, our thin atmosphere, while fish sense vibrations that pass through their dense, liquid environment. I believe the “sixth sense” talked of in the research is much like hearing because it relies upon sensing movements in the water. Here’s the nitty-gritty of how the sense works:
This remote sensing system, at first glance mysterious, rests on measurement of the pressure distribution and velocity field in the surrounding water. The lateral-line organs responsible for this are aligned along the left and right sides of the fish’s body and also surround the eyes and mouth. They consist of gelatinous, flexible, flag-like units about a tenth of a millimeter long. These so-called neuromasts – which sit either directly on the animal’s skin or just underneath, in channels that water can permeate through pores – are sensitive to the slightest motion of the water. Coupled to them are hair cells similar to the acoustic pressure sensors in the human inner ear. Nerves deliver signals from the hair cells for processing in the brain, which localizes and identifies possible sources of the changes detected in the water’s motion. [bold mine]
There you have it. Fish can hear/feel changes in their liquid atmosphere. Would a human equivalent be the ability to decipher the direction from where a slight puff of air has brushed the skin? Would we not only hear and see someone place a stack of books on a table, but also feel the slight wave of compressed air generated by it?
And what happens when a fish is pulled from of the water? Does “all go silent” for this sense? Or does it instead perceive a raucous of strange noises? A fishy tinnitus? I wonder.
To truly get into a fish’s head you’d have to inhabit its whole body.
