A Closer Look: The Anatomy of Aquatic Snails Explained

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 "What is this arm on my snail? Is he okay?"

Among the most frequent questions I come across regarding aquatic snails include questions about anatomy — and rightfully so! Snails have very funky anatomy, sometimes mystifying both beginner and long-time snailkeepers. While we still have yet to fully understand how aquatic snails function, there's thankfully much that we do know. Today, I'll break down the components of aquatic snail anatomy, focusing on the mystery snail. 

The mystery snail encompasses the anatomical structure present in each freshwater aquatic snail, hence my focus on this specific species.


Lola, the master of balance!


Siphon

That question asked at the beginning usually pertains to the mystery snail. What is that little tube? Most initially guess either parasite or genitalia. You'll be relieved to know that it's neither. This is their siphon!

I'll include this video I uploaded to my Instagram account for a fun summarization:

Mystery snails have both gills and lungs. They can breathe underwater, but you'll also find them at the waterline doing a little dance as they use their siphon to pump oxygen into their lungs. Here's a video of my golden mystery, Lola, oxygenating. 


You might also notice your mystery snail going about their day with their siphon extended, even though they're nowhere near the waterline. From what I've observed and from what other mystery snail keepers have told me, it appears that this is a generally normal behavior. In my experience, I don't believe it's indicative of distress. Of course, it never hurts to check your water quality if you're worried. Always go with your gut.



Sun's out, siphon's out!

Foot

Snails are gastropods (literally: "stomach foot"): this term refers to the fact that their anatomy is such that their stomach rests above their foot. Here's a diagram of my snail, Hershel, who is quite the model.


The mystery snail's foot, like other aquatic snails, is very gentle and soft. As their means of transportation, it's important to ensure that your substrate and tank decorations are smooth — jagged edges will cut their foot, resulting in injury. Sand down any rough edges of ornaments. As for substrate, I prefer sand, but so long as your gravel is smooth, that works perfectly fine. It just comes down to personal preference.

Mouth/Radula

Aquatic snails have something called a radula. I made a video about this on my Instagram account, which I'll link here: Snail Mouths.

As I explain in my video, aquatic snails have a radula. You may be familiar with the feeling of a cat's sandpaper tongue. However, cat's teeth are separate from their tongues. Snails, on the other hand, have a sandpaper-like tongue. The radula is a ribbon-like tongue decked out with thousands of chitinous teeth.

Chitin is a polymer composed of polysaccharides that ultimately forms a protective covering (e.g., an insect's exoskeleton). I admit that science is not my forte, so this is a very bare-bones explanation of what chitin is, but I wanted to try to summarize. (I'll leave a link to a proper explanation below.) 

Essentially, it includes sugar in its composition, and it's highly durable. These teeth are gentle enough to scrape up algae into the mouth, but it's also strong enough to devour sources of protein (such as dead shrimp). Not all aquatic snails eat meat, but mystery snails do.



This video of my nerite snail demonstrates how aquatic snails use the radula to eat.

In general, this leaves snails unable to truly injure each other (except in the case of excessive mating, which I touch on in this post). When I first began snailkeeping, I owned two nerite snails and a young bladder snail — I was so new to the hobby that I thought she was a baby mystery snail. Anyway, one day, I noticed that one of the nerites had scooped the bladder snail up and was eating it. I was horrified. Should I separate them? Is this just what happens? Will I hurt them more if I intervene?

Turns out, the nerite was just interested in the algae that accumulated on the bladder snail's shell. I mention this not only because it's funny, but also to say that should you notice your mysteries seemingly eating each other's shells (or other aquatic snails), don't panic. It's most likely eating algae. Mystery snails are very peaceful and will only eat other snails if they are starved for protein. This isn't a common occurrence as far as I'm aware, but I bring this up as well to underline the importance of feeding mystery snails properly. They must have plenty of food and plenty of protein.

Anus

On the opposite side of the siphon is the mystery snail's anus. This is where mystery snails poop from. I plan on dedicating another post to the specifics of aquatic snail waste, but in short, mystery snails poop often resembles a string of light-brown pellets. They poop often, so tank cleanings are integral to keeping the tank and snails healthy.

Antennae (technically sensory tentacles)

You learn something new every day. I sure did! As I was verifying some information for this post, I discovered that mystery snails do not have antennae (which is good because I struggle to spell that right haha), but rather, sensory tentacles. For the sake of simplicity, I'll continue to use "antennae," so just know that they're technically tentacles.

Captain Jack Sparrow using his feelers to explore


Mounted atop their heads, these sensory tentacles help the snail navigate their environment, as mystery snails mostly rely on their senses of smell and touch to get around. They do have eyes at the base of these antennae, but their sight isn't very strong, and they are incapable of hearing. Should one of their antenna be nipped or injured, it can regrow. Feeding extra protein is crucial for this to happen.

Shell and Operculum

All aquatic snail shells are made of calcium; specifically, calcium carbonate. This is why supplementing calcium in either water or diet (or both) is crucial to optimal snail shell growth and health. 

Mystery snails have a special trapdoor called an operculum. This brown disc is found at the opening of the snail shell. Composed of protein, the operculum allows the mystery snail to retreat into their shell and hide from predators. If starved of protein, the operculum can actually fall off, posing a major health risk to the snail. It can regrow after an extended period of time, but this leaves the snail highly vulnerable. A diet high in calcium and protein will prevent such a thing from occurring.

Conclusion

Though not all aquatic snails have siphons, for example, this general overview aims to provide a simplified guide to the nature of snail anatomy, in addition to the importance of meeting dietary needs for optimal snail health. Thank you for reading! Let me know if you have any questions in the comments below.

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