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Female elephant nose fish gets sexually ‘charged up’ by the electric aura of males of their own kind over the spark of closely related species, according to lab experiments.

For a long time, male elephant nose fish are known to lure females with the help of an electric field.

Philine Feulner, a behavioural ecologist at the University of Sheffield, UK, who led the study, said that such electric attraction could maintain genetic differences between the nearly identical fish species.

As compared to electric eels, which deliver 500-volt zaps, elephant nose fish can’t muster more than 1 volt and are thus called weakly electric fish.

The fish generate an electric current with an organ in their tail made from specialised muscle cells.

Feulner said that the resulting field helps the long-nosed nocturnal fish to find food and navigate the murky waters of the lower Congo River.

In many closely related species all living in the same vicinity, the jolts differ enough in their length, size, and frequency.

And Feulner and her colleagues managed to easily measure the difference with an electrode inside the fish’s aquarium. They could even mimic electric pulses of different species using a simple set-up.

Campylomormyrus compressirostris females spend most of their time near males of their own kind.

While a barrier kept the females from acting on their desires, but that didn’t stop fish from releasing eggs after the experiment was complete.

The researchers repeated the experiment with artificial electric fields in place of actual male fish. Again, females lingered near to the same-species signal.

Feulner speculated that the two species of elephant nose fish from the family Mormyridae might still interbreed to produce offspring, but their differing electric fields might keep interspecies sex to a minimum.

This might occur if differences in the strength and duration of electric discharges determine what and where the fish can eat.

According to Matthew Arnegard, an evolutionary biologist at Fred Hutchinson Cancer Research Center in Seattle, Washington, it was a rather good idea.

However more research will be needed to determine whether electric discharges increase species differences - or reflect them.

“That’s not really known,” New Scientist quoted him as saying.

Researchers from Rensselaer Polytechnic Institute claim to have solved the ‘Gray’s Paradox’ - how dolphins can swim so fast.

In 1936, zoologist Sir James Gray observed the sea mammals swimming at a swift rate of more than 20 miles per hour.

While studying, Gray calculated the drag dolphins must overcome to swim faster than 20 miles an hour.

And found that although dolphins lacked the muscles to swim so fast, yet they did. This was called Gray’s paradox.

He theorized that their speed possibly had something to do with their skin.

In the new study, Wei has developed a tool that conclusively measures the force a dolphin generates with its tail.

The researchers found that dolphins use 212 pounds of thrust to push themselves at more than 20 miles an hour.

“Sir Gray was certainly on to something, and it took nearly 75 years for technology to bring us to the point where we could get at the heart of his paradox,” said Timothy Wei, professor and acting dean of Rensselaer’s School of Engineering, who led the project.

“But now, for the first time, I think we can safely say the puzzle is solved. The short answer is that dolphins are simply much stronger than Gray or many other people ever imagined,” Wei added.

He videotaped two bottlenose dolphins, Primo and Puka, as they swam through a section of water populated with hundreds of thousands of tiny air bubbles.

He filmed dolphins as they were doing tail-stands, a trick where the dolphins “walk” on water by holding most of their bodies vertical above the water while supporting themselves with short, powerful thrusts of their tails.

The results show that dolphins produce on average about 200 pounds of force when flapping their tail - about 10 times more force than Gray originally hypothesized.

“It turns out that the answer to Gray’s Paradox had nothing to do with the dolphins’ skin,” Wei said.

“Dolphins can certainly produce enough force to overcome drag. The scientific community has known this for a while, but this is the first time anyone has been able to actually quantitatively measure the force and say, for certain, the paradox is solved.”

At peak performance, the dolphins produced between 300 and 400 pounds of force.

Wei said the research team will likely continue to investigate the flow dynamics and force generation of other marine animals, which could yield new insight into how different species have evolved as a result of their swimming proficiency.