People often think of slugs and make a nasty face, since the word doesn't bring any good images to one's mind. We immediately tend to think of nasty, snail-like creatures that crawl across our gardens and feed off blood like vampires. What's surprising though is that there is a lot more to slugs than just these features, which makes them come across as very interesting!
Slugs are very unusual creatures in the way they interact with their surrounding environment, the conditions they need to survive, and even in the way they reproduce. For starters, their only way of detecting their external surroundings is by means of the two feelers on their head - one is responsible for detecting light and hence acts like an eye, while the other provides a sense of smell. What's even more interesting is that both of these feelers can be retracted by the slug if it so chooses, and even if you were to completely remove them, they would grow back, much like a lizard's tail! Of course, the slug is not limited to only an eye and a nose to detect the outside world; it is also able to tell the ground it treads upon based on the nerve endings in its lower muscles which act as fingertips for humans. In order to move, the tiny mollusk moves its entire body in a wave of muscular contractions - much like a snake - and this propels it in whichever direction it chooses.
Being a mollusk, the slug shares its anatomy with shellfish, meaning that it is mostly muscular in nature. It also means that their body is made up mostly of water, which is prone to evaporate when the small creature is making its way across the ground. Because of this reason, most slugs are very prone to desiccation, which causes them to shrivel up and die in high temperatures. In order to counter this, the slug does two things. Firstly, it chooses to hide deep under the soil where the moisture content is higher in order to stay sufficiently hydrated. Secondly, when it moves across the ground, it secretes a layer of mucus directly underneath it which acts as a buffer between the slug and the ground. This layer not only protects the slug from being dehydrated, it also contains special fibers which allow for better grip - thus allowing slugs to climb vertical surfaces without slipping! What's even more fascinating is that some species even use this mucus trail to identify potential mates!
Slugs are hermaphroditic - they possess both male and female reproductive organs. This means that in a mating ritual, either of the two can assume the male role and the other will automatically become the female! Once mating is completed, the female lays roughly 30 eggs deep into the ground or in an area where the moisture content is high, thereby protecting it from the fate of drying up as well.
One thing that is most pertinent is the fact that slugs are often categorized as snails, which isn't entirely true. According to the true definition, a snail must possess a shell large enough for its body to comfortably retract in, which is something the slug does not have. And besides, with so many cool features borrowed from so many fascinating creatures, the little slug deserves its own recognition!