Do Spiders Have Lungs? The Complete Guide

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Mexican red-kneed tarantula

So, does your pet spider have lungs? The quick answer is that they do, but they are different to how you may imagine them to be. Also, their location is different as well. In short, they do have lungs, but they are not like most creatures or animals.

Spiders do not have lungs in a human sense, but they have something called book lungs. These resemble the pages of a book. They consist of thin layers of hollow plates. They are open to the air, and they allow air to come into the body of the spider.

In this post, I am going to give the complete guide on not only what constitutes lungs for a spider, but also how they work and where they are located. By the end of it all, you will be an expert on how your spider breathes, and it is far more interesting than most people will generally expect it to be.

So, let’s begin with the simplest of questions, and that’s dealing with this whole issue of your spider having lungs.

Yes, Your Spider Does Have Lungs – Well, Sort of

The first thing to note is that your spider does indeed have lungs, but how many depends on whether they are a more modern spider, or an ancient species. Yes, both do exist, and it’s all a sign of the way in which evolution has played a role in the development of the spider.

The spider has something called book lungs, and the ancient species will have two sets of them. The modern spider has evolved slightly since then, and they only have one pair of book lungs. However, the other pair has been able to evolve into trachea. That means they have small, narrow tubes running through their body, and they are designed to make it easier for the oxygen to get around the body and to help your spider to breathe.

These book lungs are impressive, so let’s look into them in a bit more detail.

More About Book Lungs

They are called book lungs because they resemble the pages of a book, which makes sense, and they form the core way in which a spider is able to breathe. However, don’t think that this applies to each and every species, as that’s not the case. [Source]

These lungs consist of thin layers of hollow plates. The surprising thing is that they are open to the air, and they allow air to come into the body of the spider. They will expand and contract, like our human lungs do, but they never fully close at any point.

The size of these book lungs will also vary quite widely. The plates come in pairs, and they can range from having 10 pairs up to 80 pairs, and that’s a huge difference. These leafy pages are very fragile in some ways, and yet the fact that they are kind of open to the outside world does then go against this idea. However, the key point here is that they work almost like a set of bellows to allow air to move in and out of the spider.

They manage to do this by creating what’s known as an air space between the pages. The surface of the lungs are also perfectly designed to allow that all-important exchange of gasses to occur within the pages before it’s then transported throughout the body.

The intention of the book lungs is to provide the spider with a large enough area for that gas exchange to take place that allows the spider to live. If you want to have an idea as to how large it can be, then a Tarantula will have a surface area of somewhere in the region of 70 cm, and that’s huge considering the overall size of the spider.

Their Location and Those Slits

These book lungs are generally located on the abdomen of the spider. They are in small, hard pockets in order to protect them, but do remember that the slits are always open to allow air to get into the lungs.

These lungs tend to sit more to the front of the spider, but that’s not something that applies to every single species. When you have over 38,000 species out there, it does allow for some variation to occur, so you will find some spiders where their lungs are more toward the back of the abdomen.

However, the one thing you can be certain of is that they are never anywhere else, just the exact positioning on the abdomen is called into question at times.

Now, when we say they are open, we don’t mean there is some gaping hole and these lungs are poking through. They are microscopic slits that are still able to allow air to come into the lungs, but it’s not going to put the health of your spider at risk. We know the idea of some open hole sounds horrible, but that’s really not the case in this instance.

However, we mentioned earlier on that some spiders also have trachea, so what are they and how do they relate to how a spider is able to breathe?

What About Trachea?

So, what about the trachea? You may be familiar with the word, as we have trachea as part of our own breathing system, but the spider version is a bit different to the rest. Also, the number that a spider will have is also something that varies depending on the species, but no matter the number, they are all designed to do the exact same job.

What we are talking about here are small breathing tubes, and a number of both spiders and insects have them in order to help them to breathe. They are almost like the transport network, and of course it works the same sort of way in us humans. [Source]

These small tubes are actually lined with another substance called ‘chitin’ and the reason for that is to offer some additional protection to the tubes to prevent them from being damaged.

As these tubes allow air to move throughout the body, it does provide air to the entire spider. However, the trachea then does something special in that it allows the air to pass through it into the tissue and organs, effectively keeping the spider alive.

But do remember that not every spider has trachea, so their breathing system has to work slightly differently to how you would expect.

Brown hairy tarantula on a log

But Things Get Complicated

But wait a minute, because things are going to get a bit more complicated now.

You see, with so many species of spider out there, it does mean there are some variations even when it comes to this entire usage of trachea to help with breathing. Actually, when you look at the different species, it does seem that there are five different types of breathing apparatus in the spider world.

Now, not all of them actually involve lungs, but we can quickly look at each one to show you the differences that occur in the natural world.

One Solitary Pair of Book Lungs

First, we have the solitary pair of book lungs. These are more common in the Pholcidae species of spiders. Of course, they tend to be smaller, but it does seem to be the case that size doesn’t matter when it comes to breathing.

Two Pairs of Book Lungs

Next, we have two pairs of book lungs, and no trachea. This is mainly found in the Mesothelae and Mygalomorphae species. That does mean Tarantulas and trapdoor spiders have two pairs of book lungs.

One Pair of Trachea

Some spiders only have a single pair of trachea for their breathing, and even though that sounds strange, it’s still something that really works for them. This particular form of breathing is most common in the Symphytognathidae spider family. That means 73 different species have this type of breathing, which is a small number out of over 38,000.

Two Pairs of Trachea

Another set of spiders have two pairs of trachea as their breathing system. This system is found in the Caponiidae family.

A Pair of Trachea and a Pair of Book Lungs

The final option is a pair of trachea along with a pair of book lungs. This breathing system is the one that appears in the overwhelming majority of spider species. Wolf spiders along with orb weavers are just two examples.

How Their Respiratory System Works

So, even though there are so many options, how does the respiratory system generally work on a spider? Actually, a spider has four different functions.

First, the book lungs, along with the spiracle are generally located toward the front of the abdomen of the spider. If the species has trachea, then they are mainly located towards the rear of the spider.

But even that’s not always the case. In fact, there are some species where the position of the two is reversed, and that shows the amazing diversity within the spider world.

When they have book lungs, these lungs are covered in something called haemolymph. This is something that is very similar to hemoglobin, which is used to carry nutrients around the body. These book lungs expand and contract, followed by oxygen being filtered and made ready for absorption. At the same time, the book lungs also allow for carbon dioxide to be released, in the same way as our own lungs do.

Getting More Scientific

Getting a bit more scientific for a moment. When the oxygen enters their body, a substance called hemocyanin takes over. What hemocyanin does is it helps to carry the oxygen, and then carbon dioxide, throughout the body and within the haemolymph. Hemocyanin is actually a pigment, and it’s filled with protein, but its main aim is to just make the entire process run far more smoothly than it would otherwise do.

Movement is Essential with Breathing

One thing that may be surprising for some people is that movement is very important when it comes to breathing for a spider. They need to move for their book lungs to work in the way that the spider requires.

You see, movement helps the book lungs to expand and contract. Movement gets air into the lungs and allows it to circulate.

But there’s something else you should know about breathing and spiders, they don’t need to do it that often.

A spider can sit still on their web for an extended period of time because they can go hours, or sometimes days, without breathing. This is because they don’t require a constant supply of oxygen like we do. However, it still plays a role in keeping them alive even though it’s very sporadic.

So, In Conclusion

Basically, spiders do have lungs, but not every spider has them. It all depends on the species in question. Also, don’t stress if your spider doesn’t move for a prolonged period of time after learning they need to move in order to breathe. They are a well-oiled machine, and they know exactly what they are doing.

No matter if it’s two pairs of book lungs or just trachea, your spider is able to get the correct amount of oxygen into its body and for it to then be converted into everything it needs.

Spiders breathe differently from most creatures, but it’s an approach that works well for them in life. Also, don’t worry about potentially damaging those lungs on your pet spider, They are a lot hardier than they may initially seem.

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