Fish species that evolved on opposite sides of the Atlantic Ocean developed the ability to generate electricity in a similar way and around the same time, according to an international team of researchers.
The scientists, including Masaki Miya, head of the zoology department of the Natural History Museum and Institute, Chiba, analyzed mitochondrial DNA of gymnotiforms, a group of South American electric fish species, including the electric eel, and of mormyroids, a group of similar species in Africa.
The results showed that the species’ common ancestor lacked electrogenic capacities. But both species groups acquired electroreceptor organs around 110 million years ago after the African and American continents started drifting away from each other. They subsequently developed electrogenic organs for defense against predators and for mutual communication, the scientists said.
"The electroreceptor organs and the electrogenic capacities probably developed under environments that impaired the field of vision and hampered communication," Miya said. "That's probably why they acquired the same capacities independently."
The species were collected from the Amazon and the Nile rivers, which are both muddy. Combinations of species from both habitats that have similar feeding habits emit different electric signals but look strikingly similar.
The research results were published on May 14 in the PLoS ONE scientific journal.
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