Great question! That horizontal “blink” and the three oval pupils are various tricks of the light as it bounces off the mantis shrimp’s triple-banded, highly-faceted eyes!
Mantis shrimp do not have eyelids, so they don’t blink—but they do clean their eyes frequently to keep things 20/20!
The eyes of mantis shrimp have three bands, each with a focal point. One mantis shrimp eye is therefore tri-focal, meaning they have depth perception with just one eye! Those three focal point “pupils” appear when the eye is looking toward the camera.
Each band is sensitive to different types of light, including polarized light, allowing mantis shrimp to see and communicate using visual signals that play across a huge visual spectrum!
Thanks again for the great question!