Difference Between Snail and Slug

Introduction

If we talk about a story that says slow and steady wins the race, we always remember the story of the rabbit and tortoise. But there are many more creatures present on our planet whose speed is really slow but they are also important for nature and plays an important role as well. Snails and slugs are one of them. Snails and Slugs both are mollusks. They belong to the same group that includes octopuses and oysters and belong to the gastropod family. Then how snails and slugs are different from each other? In this article, we are going to discuss such facts. What is the difference between a snail and a slug, are they the same, or are they different creatures altogether, why do snails have shells and slugs don’t, are Slugs related to snails, etc.

Snail vs Slug

As we have already read, snails and Slugs belong to the same family of gastropods, they are different from each other. Snails have evolved a handy portable capsule on their backs. Some slugs also do have shells, but we rarely see them, because they spend most of their lives underground, chasing earthworms, while others have nothing at all. The shell of the snails provides some form of protection from smaller predators, but more importantly, it allows them to slither into a world of their own. On the other hand, slugs spend most of their life underground and don’t require any shells.

Difference Between Snails and Slugs in Tabular Form

Parameter of Comparison	Snail	Slug
Definition	Snails are mollusks who have shell in their back.	Slugs are mollusks but don’t have a shell.
Types	Sea Snail  Freshwater Snail Land Snail	There are more than 60000 species of slugs.
Features	They have a hard shell on their back.	They don't have shells.

What is a Snail?

Most snails that crawls across the ground are harmless creatures with a shell on their back. This is usually the only picture that most people have of snails, however, not all snails are like this. Some snails inhabit the water swimming underneath or along the surface during a low tide, some snails live in the aquarium.

Interesting Facts of Snails

• Snails are not insects. They crawl underground much like insects do, but they are gastropods.
• Gastropods make up over 80% of mosques. Mosques are soft-bodied invertebrate clams, oysters, and octopuses are a few examples. However, gastropods like snails still outnumber the list.
• Contrary to popular belief, snails and slugs are not the same. They belong to the same category, but still, they are not the same. There are a lot of different snail species.
• A fully preserved snail dates back to 99 years ago. Mostly the complete snail fossil was recovered from Myanmar in 2018. It still had its shell, head, eye socket, and foot. Most fossils only survive with the shell so this fossil was a special and historic find.
• The smallest snail in the world is found in China.
• The world’s largest snail is the giant welk, the Australian great wealth 70cm in size. It is three times bigger than most African land snails.
• Baby snails are born with a protoconch. A protoconch that is the earliest shell is a soft and transparent shell that baby snails are born with. As they grow older and consume food with calcium in it, the shell becomes harder.
• Snail shells cannot be replaced. A snail shell acts as its home and protects the snail’s organs from harm. Snails cannot recover from a completely broken shell.
• While most snails do, some snails do not have two eyes. There are snail species that do not have eyes at all. All the underground snails use their tentacles and other senses to move around.
• A snail doesn’t have jaws. Their mouth does not change with a jaw nor do they have teeth or fangs lined up as most animals do.
• Despite not having jaws, snails have the most teeth out of any animal. It depends on the snail species but a snail’s raglan is lined with up to 20000 teeth. Further-more snail teeth are incredibly strong. The strongest natural material in the world is found in marine snails’ teeth. It was five times stronger than spider silk.
• Snails move using only one foot. They crawl across the ground as snakes do, however, they don’t use their bellies to move around, instead, snails use one muscular foot. They secrete a lubricant that eases their movement and also protects their bodies from rough surfaces. 
• One day is not long enough for a snail to cover a distance of 1 mile. Snails are known as fast creatures they are some of the slowest creatures out there. On average a snail takes up to 33 hours to cover a single mile.
• Snails can move faster if they are trailing behind another snail. Since a snail leaves a trail behind in their way, another snail can use this to move faster. The existing trail makes it easier for the snail to move fast around because of the added traction.
• The fastest snail alive is likely the plow snail. The plow snail is a sea snail that knows how to use ocean waves to its advantage. When the timing is right the plow snail flexes its foot much like a boat sail, this causes the snail to move 2.5 cm as opposed to the usual one cm per second.
• Freshwater snails are asexual. Since most freshwater snails have both egg and sperm cells, they can reproduce by themselves. This also makes it very easy for them to multiply over a short time.
• A snail usually lays over a hundred eggs in one clutch. Despite the large number, only a few survive. Usually only around 20 to 50 of these eggs hatch and mature into adulthood.
• Unfortunately a third of snails die after laying eggs. Some snails do not survive long after giving birth due to excessive stress they have put during laying a hundred eggs.
• Garden snails are nocturnal creatures.
• A snail’s nap can range from a few hours up to three years because snails need moisture to survive, they will sometimes sleep when the weather gets too hot and dry.

Types of Snails

There are over 5000 species of snails. They are classified into Three mail groups as-

1. Land Snail - The land snails are again sub divided in many species like Giant African Land Snail, Mediterranean Green Snail, White-Lipped Snail, Croatian Cave Snail, Garden Snail, Roman Snail, White Garden Snail, Milk Snail and Candy Cane Snail.
2. Freshwater Snail - Freshwater Snails are also divided into species like Mystery Snail, Channeled Apple Snail, Red Nerite Snail, Golden Apple Snail, Rabbit Snail and Colombian Ramshorn Apple Snail.
3. Sea Snail - Sea Snails are sub divided in Common Periwinkle Snails, Geography Cone Snails, Hairy Triton’s Trumpet, Common Whelk, Violet Sea Snail, Limpet and Sea Butterfly.

What is Slug?

Technically slugs and snails are the same. Most people call any of these with a visible shell a snail and any without a visible shell a slug. But taxonomically speaking there are some slugs more closely related to certain snails than they are to other slugs, so their classification goes more than shell deep plus sometimes there are slugs who look like a cross between a slug and a snail. These are usually referred to as semi-slugs. They do have shells but they’re no longer able to curl up inside them the way a snail would. Slugs travel on slime trails. These slime trails are produced via released mucus and the slugs move around using a muscular foot to sense their surroundings.

Interesting Facts of Slugs

• Slugs can reach one-fourth inch to ten inches in length, depending on the species.
• Slugs can be a yellow, brownish, whitish, grey, or black-coloured body that is often covered with different dark markings.
• Slugs don’t have teeth. Instead, they have radula which is an organ composed of thousands of miniature protrusions that helps them in grinding of food.
• Slugs have two pairs of retractable tentacles on top of the head. The light-sensitive eye spots are located on top of the long tentacles.
• Sense of smell and touch in slugs are located on the short tentacles. Each lost tentacle can be regenerated.
• Slug can flatten its body vertically and can elongate it 30 times when it needs to enter small hole or crack.
• Unlike snails, slugs don’t have a shell. Their body is one strong, muscular foot covered in slime that helps them in movement on the ground and prevents their body from injuries.
• Slugs can move across the rocks and other sharp objects including the blades and knife.
• Slugs produce chemicals in the slime to find their way to home. Dried slime leaves a silvery trail which they follow.
• Slug has only one lung. It is connected with the atmosphere by a tiny opening on the right side of the body. Besides via lungs, the slug can breathe via skin.
• Slug spends most of the time in cool and moist underground tunnels. It emerges at night to feed on leaves, speed sprouts, roots, and decaying vegetation.
• Some species of slugs are carnivores. They feed on other slugs and earthworms.
• Slugs avoid hot weather because it easily loses body water. It is most active during the spring and autumn.
• According to some studies in the UK, one cubic meter of garden contains 200 slugs. One acre of farmland contains approximately 300.000 slugs.
• Slugs contain both male and female reproductive organs. Even though they can produce offspring on their own, they prefer to find partners and exchange packages of sperm.
• Slugs lays 20 to 100 eggs on the surface of the soil couple of times per year. One slug can produce up to 100.000 babies in a lifetime.
• Incubation period depends on the weather conditions. Eggs sometimes hatch after a couple of years of dormancy.
• Slugs can survive from 1 to 6 years in the wild. Female slugs live longer than males.
• A slug’s body is around 80 to 90% water.
• Slugs make mucus on their own.

Types of Slugs

There are more than 60000 species and subspecies of slugs. Some common species of slugs found in gardens are The Brown-Banded Arion, European Red Slug, Black Green House Slug, Marsh Slug, Large Spotted Garden Slug, Grey Garden Slug, European Slug, Native Reticulated Slug, Great Grey Garden Slug, European Black Slug, Milky Slug, banana Slug, Spanish Slug, Dusky Slug, Balcon Thread Band Slug.

Main Differences Between Snail and Slug in Points

There are not so many differences that we can find between a snail and a slug as they belong to the same gastropod family, and both the snails and slugs are mollusks.

• The Major difference between them that is visible from the outside is the hard outer shell which is present at the top of a snail and absent in a slug.
• Although a few slugs also have calcium shells they are rare. Slugs can live without shells and can re-grow their tentacles whereas snails can’t repair their shell if they got broken and can’t grow back their tentacles as well.
• Slugs always prefer to live underground to keep their body moist whereas Snails lives on the ground because their shell helps to provide nourishment and moisture to the body.
• Another difference between them is the teeth. Snails have more than 20000 teeth whereas slugs don’t have teeth at all.

Conclusion

Always remember slugs play the most vital role in their ecosystem because they eat dead matter from the forest and recycle it into nutrient-heavy waste that acts as a fertilizer. On the other hand, snails are important players in the process of forest decomposition and also contribute to the nitrification of soil through their decaying shells, feces, and body. Snails are the prey for a number of vertebrates as well as invertebrates.