When the researchers performed post-mayhem postmortems on the fish, they found that the levels of testosterone and another hormone associated with aggression circulating in the cichlids' bloodstreams were comparable regardless of whether the foe was a reflection or flesh.
But in dissecting a part of the fishes' brain called the amygdala, they found evidence of substantially more activity in that region in the mirror-fighting fish than in those tussling with real foes.
"The amygdala is a part of the brain that has been associated with fear and fear conditioning, not only in fish, but across all vertebrates," Desjardins said. So the fish appeared to feel an element of fear when confronted by an opponent whose behavior was off-kilter.
Although higher vertebrates such as humans have very elaborate amygdalas by comparison with fish, there is still a part of the more complex amygdalas that is analogous to what fish have and performs similar functions.
"The fact that we saw evidence of a really high level of activity in the amygdala, is pretty exciting," Desjardins said. "And surprising."
"I thought I might see a difference in the behavior and when I didn't see that, I was pretty skeptical that I would see anything different in the brain," she said.
But she thinks what they found is evidence of a negative emotional response and offered what she emphasized is a speculative comparison. Perhaps it is "like when you are a little kid and someone keeps repeating back to you what you have just said, that quickly becomes irritating and frustrating," she said. "If I was going to make that giant leap between humans and fish, it could be similar."
So what does this tell us about a fish's level of consciousness?
|Contact: Louis Bergeron|