Polka-dot boxfish (juvenile)

The boxfish are related to the pufferfish and found in the same super-family, the Tetradontidae. In these pictures show juveniles, a younger individual in picture number three. When they reach adult stages the polka-dot boxfish (also known as yellow-spotted boxfish) turn brown and as they mature they develop the characteristic box shape. The younger juveniles (pic no. 3, ca 2 centimeters long) are more round.

The bright yellow colouration is called aposematic colouration, meant to deter predators by warning them that they are toxic.