How Spiders Breathe
Have you ever wondered whether or not spiders breathe? If so, have you ever wondered how their respiratory system works? Well, first, spiders do breathe. They just do not breathe like mammals and other animals do. They do not take a breath through their mouth like humans do but instead they breathe through their skin on the underside. Compared to man's own respiratory system, they have an what is called an open respiratory system
5 Types of Respiratory Systems in Spiders
- A single pair of book lungs, as within the suborder Pholcidae.
- Two pairs of book lungs, as within the suborder Mesothelae and the infra-order Mygalomorphae
- One pair of tubular trachea only, or sieve trachea to some spiders, such as the Symphytognathidae spider family.
- Two pairs of tubular tracheae, or sieve trachea, as in the Caponiidae family of spiders.
- A pair of tracheae and a pair of book lungs, as in wolf spiders and orb weavers. This is also apparent in a majority of spider species.
Please Note: Some scientists do not believe there is much of a difference between tubular tracheae and sieve tracheae to classify them differently. However, you will find that other scientists do make the distinction between the tubular and sieve tracheae.
Spiders have four respiratory functions that work together to enable the spider to breathe. The book lungs and the spiracle of the book lungs are located at the anterior end, which is the front end of the spider. For spiders with a trachea, the trachea is located at the posterior end, which is toward the back end of the spider. These two sets of respiratory organs vary from one individual spider species to another. Some spiders have two sets of book lungs while other spiders have two sets of tracheae. Even still, some spiders have a combination of both where the trachea is at the anterior end, and the book lungs are located at the posterior end.
Book lungs are stacks of ten to eighty hollow, leafy disks. The number of hollow disks stacked depends on the species of spider. Spiders, such as tarantulas, in the Mygalomorphae infra-order and Mesothelae suborder, have two pairs of book lungs. Scientists have found that many primitive spider species have the feature of a set of book lungs compared to just one pair.
The book lungs are saturated in light blue haemolymph. Haemolymph is similar to blood for a spider. Then the book lungs or trachea, depending on the spider, filters the oxygen for absorption and releases carbon dioxide into the air through a process called diffusion.
Haemolymph is very similar to the hemoglobin that carries iron-rich nutrients. In the case of spiders, hemocyanin, which is a protein-rich respiratory pigment, carries oxygen and carbon dioxide within haemolymph instead. Haemolymph is a light blue color due to the copper atoms it carries as well.
The tracheae are long tubes that start at small holes on the underside of the exoskeleton and extend through the body of the spider providing oxygen to internal organs. Air is absorbed through the skin or very small trachea holes located on the underside of the spider's abdomen. It is a common belief of arachnologists and entomologists that the trachea is a new feature that was integrated with genetic adaptation. Some species with this trachea feature include wolf spiders, orb spiders, and daddy longlegs.
The spider must move to allow the book lungs to work. The movement of a spider provides the necessary energy for air to be pushed in and out of the book lungs or trachea. However, spiders require less oxygen than people do. Therefore they can go hours to even days without breathing. This is why they can stay so still in their web waiting for their next meal or why you can capture a spider in a jar without holes and they can be still alive days later. So be careful the next time you choose to capture a spider specimen. It may still be alive when you open the jar days later.
Although the respiratory system of a spider is much simpler compared to mammals, the inner workings of a spider are amazing. They are very resilient creatures, so don't underestimate the survival rate of spiders. They are equipped to survive the toughest of times and circumstances. One way this is evident is in the way they breathe, and yet can go for hours without breathing at all.
© 2014 L Sarhan