eyespot

noun

1. (countable)Any of various primitive light-sensitive organs or regions in many diverse organisms.

   “The eyespot is a complex sandwich of membranes with rows of granules that contain around 200 different proteins, including the same rhodopsins found in the retina of our own eye.”

2. (countable)An eye-like marking on the tail of a peacock or the wing of a butterfly.
3. (countable)A coloured spot in a motile gamete or spore, which is sensitive to light.
4. (countable, uncountable)Any of a group of fungal infections of grasses that are characterized by oval spots; strawbreaker.