Predation and Defence

Polyclad flatworms are soft, juicy, and delicate worms. During evolution they had to evolve strategies to protect themselves from all the hungry reef animals (especially fish and crustacea) that might eat them. One general principle is camouflage which means in first line to become invisible by being exclusively active at night or by matching both the texture and the colour of the food they prefer to feed on. Surprisingly, some strategies involve colours! In vertebrate animals with well developed vision, such as fish, colour patterns have often evolved as signalling displays for intraand inter-species communication. Flatworms, however, have very poor eye sight and it is very unlikely that they can sense much more than light and dark and passing shadows. Thus, their brilliant colour patterns have evolved entirely for defense against predators, mainly fish, which have excellent eye sight.