Difference Between Slug vs Snail

Difference Between Slug vs Snail

The most common fact about invertebrates is their lack of backbones, but you would be amazed at how insignificant this piece of information is when it comes down to describing them uniquely. The reason is that there are over a million species known and scientists believe that there are many more that are unknown. Some of them are so similar, especially in their physical properties, that they are often confused for each other. A very good example is in the slug vs snail comparison.

After careful research, we gathered some information that can help to differentiate these two, regarding their appearance, pattern of movement, economic importance, and lots more. But before we get into that, here is a descriptive summary of the two.

Definition of Slug

A slug is defined as a mollusk characterized by its biological ability to secrete a thin layer of liquid that acts as a protective fluid. It has a tough skin to cover up for its lack of shell, which is a major difference between slug and snail.

According to scientists, some of the subspecies of a slug have reduced shells or an internal one. In addition to that, they all have the following features in common.

  • A saddled-shaped mantle right behind the head which holds the anus, genital, and respiratory opening.
  • A couple of retractable pairs of tentacles for smell and sensory perception
  • The vestigial shell, which is internalized and used for storing calcium
  • The tail, which comes right after the mantle
  • A flat underside, which works as the foot

This animal is known to feed on leaves, mushrooms, lichens, and other forms of organic materials. They may have no positive economic importance in a farm considering their parasitic nature as pests. However, some scholars argue that the mucus they secrete might be of benefit to plants.

Definition of Snail

A snail is defined as a mollusk with an external shell to house its complete body. Like every other invertebrate, it does not have any backbones, and like slugs, they also secrete a form of fluid that helps them to breathe.

There are quite a number of subspecies of this mollusk, including the sea, freshwater, land, and African giant snails. The difference in these subspecies can be seen in their size, habitat – either terrestrial or aquatic, color, and a number of other features. In addition to that, they have the following common traits:

  • A flat under layer foot for movement
  • Male and female reproductive organs
  • Two pairs of tentacles that are retractable for sight and sensory
  • The outer shell for protection when threatened
  • A mantle located towards the exterior

Another thing that the snail and slug have in common is that they are both hermaphrodites. They share some features like the tentacles, compound eyes, ability to secrete mucus, and so on. On the average, they live for two to three years, which is about half the lifespan of a slug.

Main Differences Between Slug vs Snail

The table below is an attempt to summarize the basic difference between slugs and snails. Aside from the reference to external shells, we would also look at them considering their habitat, movement, color, length, etc.

Basis of ComparisonSlugSnail
DefinitionA mollusk characterized by its biological ability to secrete a thin layer of liquid that acts as a protective fluidA mollusk with an external shell to house its complete body
HabitatTerrestrialTerrestrial or aquatic
ColorBlack, yellow, or greyMostly gray in color with a brown, white, or black shell
MovementManeuverable and compressibleSlightly stiff and incompressible
ReproductionCan carry less than thirty eggs at a timeCan carry up to one hundred eggs at a time
SubspeciesAbout 20Over 60
LengthGrows up to 15 inches longGrows up to 10 inches long
LifespanSometimes more than 6 yearsAbout 2 to 3 years

Difference Between Slug and Snail: Conclusion

Without the shell, it would probably be a tough task doing a snail vs slug comparison and trying to tell the difference on a face level. However, we hope that the much we have shared is enough help in differentiating between these two.