The following video shows a snail waving its tentacles around to find out what’s going on and how the snail retracts its tentacles when they are touched: This pulling in of the tentacles is called retracting, so slugs and snails can draw back and hide their tentacles whenever they want. If a slug or snail touches something with its tentacles that it doesn’t like or that might attack it, the slug or snail pulls its tentacles back into its body for protection. They also use smell for this, which we’ll talk about in a bit.
When they do this, they feel where they are, where they’re going, and they learn their way around an area. Slugs and snails use their upper tentacles to see what little they can, but they “see” better by touching things with their tentacles. With such bad eyesight, how do slugs and snails see where they’re going?
They also can’t see colors.īut we do know that slugs and snails can see changes in light, which tells them when it’s day time for sleeping and night time to come out, and when the days are getting short enough for snails to go into hibernation. But slugs and snails don’t see like we do because they don’t have the same eye muscles or cells in their primitive brains to interpret what they see.Īs far as experts can tell, slugs and snails can’t adjust their pupils to focus on things near and far, so things far away and nearby are probably very blurry for them. Slug and snails’ eyes are quite well developed, with a retina, lens, and optic nerve, like there are in human eyes. How slugs and snails use their tentacles to see As a result, slugs and land snails are very similar and use their tentacles in pretty much the same way. So some water snails became land snails and some of these land snails became slugs.
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Over time, evolving land snails grew smaller shells (semi slugs), or made their shells so small that they are hidden under the skin on their backs or disappeared completely (slugs).Ĭlick here to read about this amazing transformation and why snails have shells and slugs don’t.
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Once land snails learned how to live on land successfully, some of these snails evolved again – into slugs. The upper tentacles can also move independently, which means that one tentacle can point in one direction and the other tentacle can point in another direction.Īll of this movement is important because land snails crawl a lot further than water snails, so they need to see more and watch out for more dangers, like predators who want to attack them. With eyes at the tips of their long tentacles, snails can move their tentacles to see much more around them. As these snails adjusted to living on dry ground, their eyes moved from the base of their tentacles to the very tips of their tentacles and their tentacles became retractable (more on that a little later). Over a long period of time, some water snails adapted to live on land. With their eyes fixed firmly to their head, water snails have a very limited range of view. Water snails have only two tentacles on their head (not four like land snails), with eyes at the base of these tentacles. These tentacles have changed quite a bit over time…Īll snails started out living in water, and many snails still live in water. There is a light-sensitive eye at the tip of each long tentacle and cells in the tentacle that can smell. The tentacles higher up on a slug or snail’s head are the longer tentacles.
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