2 min readfrom Marine Biology Subreddit

Do angelfish tilt their bodies to reflect sunlight into the eyes of invading angelfish?

Hi, I recently came across the following interesting passage about angelfish in Andrew Parker's book "In the Blink of an Eye: How Vision Sparked the Big Bang of Evolution":

"Angelfish live in the clear surface waters of the Amazon. They have flattened bodies with silver skin, similar to a mirror. When one fish invades another’s territory, the defender leaves the shelter of reeds to do battle. Battle stance is a tilted position in the water column, with the aim of firing sunlight into the eyes of the opponent. Like Roman shields, the strong Amazonian sunlight can be concentrated into a narrow beam and directed precisely. In fact both fish in this combat take up their positions in the open water, fine-tuning their lines of fire by adjusting the tilt of their bodies. Light flashes through the water like the lasers of Star Wars battles. The stakes are high. A direct hit in the eye can lead to the bursting of blood vessels and an increase in heart and breathing rates. A fish defeated in this manner is at best temporarily stunned and at worst killed. Either way, the battle is over. This is a fish living in waters where sunlight is at its most intense, and it has adapted. Acting on this strong selection pressure, it has evolved precision mirrors."

I was hoping to find a video of angelfish doing battle in this manner, but searching online, I can't seem to find any other sources describing angelfish behaving like this. Now I'm unsure whether or not this is even true (it does sound way too cool).

Does anyone know if Parker's depiction is accurate or just a romanticization of angelfish behavior?

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