How do spiders breathe?

1 Answer
Mar 21, 2016

Sipders have two system of respiration, the book lungs and the tubular tracheal.


First let's talk about the book lung.

This structure is situated in a "pocket" on the ventral side of the opistrosoma (abdomen). he name "book" come from it's shape which remind of the page of a book. This shape grant a hight ratio surface/volume, meaning that there is a lot of contact surface with air stored in a little space. Those " page" have a very thin structure that allow oxygen in the air to diffuse inside the spider's hemolymph just like it happend within our lungs to our blood.

The other structure are the tubular tracheal.
Those are tubes that have an opening ventraly, They could remind of the stigmat of insects but they are less effective. Insect's stigmats divide themself in several little tube that bring oxygen dirrectly to cells, in spider it supply the hemolymph only which then transport oxygen throughout the circulatory system.

Those tube vary a lot in size and shape depending on the spider's family with different strategy. For instance salticid spider, which have a great vision and tend towars analysing it's environnement, have their tubular tracheal extend to suply their nervous system.

Most ancient spider don't have the tubular tracheal but two pair of book lung (ex: tarentula). most have both the strutures and some are exeptions (like often in biology), for instance the daddy long leg (Pholcidae) only have a pair of book lungs but no tubular tracheal.

Foelix, R. F. (1982). Biology of spiders. Harvard University Press.

Nentwig, W. (Ed.). (2013). Spider ecophysiology. Springer Science & Business Media.