What Happens When a Slug’s Eyestalk Touches Water?

Slugs are fascinating creatures known for their sliminess. Slugs have eyestalks that protrude from their bodies, positioning the eyes away from the main body. This is very different from humans and raises questions about how slugs protect their eyes. With their eyes so exposed, what happens if they get water on them? How do slugs keep their eyes healthy? This video by Nature Picture Library shows what happens when a slug’s eyestalk touches water, causing a sudden retraction. Read below to learn how this happens and when it occurs.

Slugs Retracting Eyestalks

The eyestalks on slugs serve a few purposes. The first is for seeing. The pair of tentacles, known as optical tentacles, serve as the slug’s eyes. These eyes are very different from human eyes; they can only detect light and dark, causing slugs to rely more on other senses. Slugs have two pairs of tentacles: the upper pair, called optical tentacles, is used for seeing, while the lower pair is used for smelling and tasting. If the light-sensitive tips of the tentacles are damaged, they can be regrown, highlighting their importance in a slug’s life. With how important the eyestalks are, why do they retract?

Slugs retract their eyestalks when they sense potential harm. This action is not painful for them. When exposed to water, as shown in the video, or to other potentially harmful stimuli such as physical touch, the slug will retract its eyestalks. This is a simple muscular movement that keeps their eyes safe. The best way to think of it is as blinking. When something gets in your eyes, it is common to blink rapidly to remove it, or when something is flying toward your eyes, you shut them tightly to protect them. A slug’s eyestalk retraction serves the same purpose.