eel

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Sounds like a strange toy or home knick-knack, doesn’t it? Actually, this does apply to real fish, including eels and sharks.

Scientists have discovered that the fish that are able to generate electric fields for purposes like fighting, navigating or mating, have a battery-like organ in their tails. Within this organ, a dimmer switch of sorts has been detected, as part of cells called electrolytes. The switch comes in the form of sodium channels. The fish uses these channels by inserting or removing them from the electrolyte membranes; the more channels that are used, the stronger the electric impulse will be.

Further investigation shows that when serotonin is released in the fish’s brain, it triggers the release of the adrenocorticotropic hormone from the pituitary gland. This in turn triggers the device that sends more sodium channels to the membrane. So, when the fish become inactive, they are able to reduce or dim the intensity of their electric fields by removing the sodium channels from the membranes.

“By adding new ion channels to the electrolyte membrane only during periods of activity or social encounters and removing these channels during inactive periods, these animals can save energy and reduce predation risks associated with communication,” the researchers write in the Sept. 29 issue of the journal PLoS Biology.

I don’t know about you, but I’d say that’s quite a shocking discovery!