If you’re curious how many noses does a slug have, you may be surprised to learn that they don’t really have one at all. Instead, slugs have four sensory organs that look like they should have a nose and serve different functions.
The most obvious “nose” on a slug is actually a gaping hole, called a pneumostome, on the right side of their bodies. This opening is used to move air in and out of their single lung, allowing them to breathe even in moist environments where oxygen levels might be low. The slug’s large lung-like structure is also a defense mechanism against predators, as they can release a foul-smelling slime that repels insects and other potential prey.
Eyes on a slug are found in the form of eyespots at the end of two retractable pairs of tentacles. The upper pair, known as optical tentacles, are used for sight and have light-sensitive eyespots on the ends that can grow back if they’re lost or damaged. They can’t detect color or shape as well as humans can, but they can distinguish between bright and dark hues.
The lower tentacles, on the other hand, are used for touch and smelling. They can move in rhythmic waves to help the slug navigate their way around their environment, and they can also create a layer of mucus that helps them find their way home after leaving their tunnels or feeding sites. This mucus is also a defense against predators, as it will stick to any insects that come too close.