14 DAY TRIAL // A fairly big number of fish species, including eels and sharks, has the ability to generate and discharge electrical currents in the water around. The ability is used either to stun prey, or for defensive purposes, depending on the situation. Now, a new study has revealed that some of these species are also equipped with dimmer switches, whose purpose is to turn down the electrical activity in the fish, so as to preserve energy. The switch addresses the battery-like organ most electric fish carry in their Tails, LiveScience reports.
Naturalists and biologists have known for a long time that generating electrical impulses is a very energy-consuming process for the fish, and, naturally, it would be unsustainable for the animals to keep themselves on alert all the time. In the new investigation, a species known as Sternopygus macrurus has been analyzed. For example, this fish needs to be active during the night, and must avoid electrical field-sensing predators, such as the catfish. Without the ability to turn down its electricity, it would surely become food for the predator.
While looking inside the electrical organ, during the latest study, experts have observed dimmer switches, located in the membrane of electrocytes. These are the cells in which the electrical charges build up, before they are channeled into the surrounding environment. Observations have shown that the fish is basically able to control the amount of sodium channels that form in the electrocyte membrane. More of the chemical means a powerful electrical current, whereas less translates into a weaker discharge. The current electric fish emit can range between eight and 220 volts, depending on its purpose and the circumstances it's being used in.
Investigators have also noticed that electrocytes always have a reserve of sodium channels. This allows the fish to rapidly modify the intensity of their charge, within two to three minutes. When a dangerous situation presents itself, serotonin is released from the brain. The chemical acts on the pituitary gland, to release the adrenocorticotropic hormone, which initiates the introduction of more sodium channels in the membrane walls.
“This is happening within a matter of two to three minutes. The machinery is there to make this dramatic remodeling of the cell, and it does so within minutes from the time that some sort of stimulus is introduced in the environment,” University of Texas in Austin expert and study researcher Michael Markham explains. According to a paper published in the latest issue of the open-access journal PLoS Biology, when the original stimulus is gone, the number of sodium channels drops considerably, making the fish “stealth” to electrical field-sensing predators.
“By adding new ion channels to the electrocyte 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 UTA team reports.