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Ask Fuzzy: To slugs, slime is sublime
Question: Why are slugs so slimy?
Slime – despite our seeming aversion to it – is important to most animals, including us. We couldn't swallow, defecate, have sex, give birth, trap foreign bodies in our breathing airways, or many other things without slime.
Slugs and snails produce slime which provides a protective buffer between their delicate thin skins and soft bodies and the outside world.
For some animals, however, it takes on an even greater role. Slugs are covered in slime which provides a protective buffer between their delicate thin skins and soft bodies and the outside world. They can increase this coating in times of danger to turn themselves into a "very difficult to swallow" meal – not many animals eat slugs!
The slime slows evaporation from their water-permeable skin and even prevents abrasions and punctures. You might regard slime as a fairly insubstantial protection, yet a slug can crawl right across, and over, the sharpest blade edge without injury.
They can do this by producing a thin film of slime at the front of the foot which coats what they are crawling on, and then muscular waves produced on the foot of the slug move the slug forwards on this slime mat, leaving the well-known "silvery trail" behind them. This not only protects the slug from abrasions if it is crawling across rough ground but also has the advantage of being sticky so the slug can climb up a smooth pane of glass with ease and even travel upside down – no mean feat for a footless animal.
The slime is even strong enough to hold the slug's body weight. If you search on the internet for "Limax maximus mating" you will see that the strand of slime is actually supporting the combined weight of TWO huge spotted Leopard Slugs.
So with all the uses of slime, the question perhaps should really be "why aren't we MORE slimy?"
You might wonder how such a soft animal is able to chew through your lettuce. They do it with their radula, which is a sort of rasping tongue made out by of calcium and therefore harder than their food. It's also how slugs can be identified without a DNA analysis – we look at the pattern of rasping "teeth" on the radula, and its shape.
If you rub a small piece of paper onto a Leopard Slug and press it against the fridge you've just created a single-use organic post-it note!
Response by: Martyn Robinson, Naturalist
Brought to you by the Fuzzy Logic science show, 11am Sundays on 2XX 98.3FM. Send your questions to askfuzzy@zoho.com