Colorful male swordfish will measure their sword size before heading into battle, and typically just flaunting their impressive weapon can make opponents flee.
Meanwhile, researchers in the United States have found that female swordfish prefer males with magnificent striped swords.
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Male swordfish. (Photo: Discovery/Vnexpress) |
From this, the research team suggests that the sword is not functional as a weapon but is instead designed to impress females. It is an extension of the tail fin, protruding like a sword.
“It is not hard and cannot be easily controlled. It is not useful as a weapon but merely serves as a visual sign in the competition,” said Kari Benson, the study’s author.
Benson, a biology professor at the University of Lynchburg in the United States, explained: “The sword may indicate many things: how strong and vigorous he is, how well he feeds, or simply that he is large.”
Researchers placed two male swordfish of similar size but with different swords in a tank and observed their interactions, mainly chasing and biting. Next, the team altered the sword size by attaching plastic pieces to the fish’s tail.
Each time, the male with the larger sword won. Typically, all he needed to do was display his sword, and the other male would retreat. “The body of the defeated male darkens due to stress, he lowers his head and backs away to the far side of the tank,” Basolo noted.
Brian Trainor from Ohio University commented: “What surprised me was that even when given a fake sword, the fish could still assess the size of their weapon.”
Trainor added: “People think fish are not intelligent. But these fish not only evaluate the size of their opponent’s sword but can also compare it to their own weapon. I think that’s an impressive result.”
He even suggested a connection between swordfish and humans, as both species develop traits that do not provide significant survival benefits. For example, the sword serves no defensive purpose other than a visual effect. Humans have artistic abilities and a sense of humor mainly to impress the opposite sex. Just like swordfish, they can outshine competitors lacking talent or wit.
M.T. (according to Discovery)
